Biomedical subjects

G Pantaleo

Publications and source records attributed to G Pantaleo.

At least 109 records · Page 6Linked to original sources

PubMed1987

Antibody-induced modulation of the CD3/T cell receptor complex causes T cell refractoriness by inhibiting the early metabolic steps involved in T cell activation.

We investigated the mechanism involved in T cell unresponsiveness that follows the monoclonal antibody-induced surface modulation of the CD3-TCR complex. We determined whether modulation of CD3-TCR affected the early metabolic steps such as [Ca2+]i rise and InsP3 formation. A strong inhibition of the increase on [Ca2+]i mediated by either anti-TCR or anti-CD2 mAbs was detected. In contrast, surface modulation of CD2 molecules did not prevent the [Ca2+]i increase induced by anti-TCR mAb. Similarly, InsP3 increase was strongly reduced only after modulation of CD3-TCR complex (but not of CD2 molecules). Therefore, it appears that surface modulation of CD3-TCR complex causes T cell refractoriness by inhibiting the very early metabolic events that follow receptor-ligand interactions.

Antibodies, Monoclonal↗

PubMed1987

Surface markers of human lymphokine-activated killer cells and their precursors. Analysis at the population and clonal level.

Lymphokine-activated killer (LAK) activity was first analyzed on PBL populations fractionated on the basis of the expression of T11 or T3 antigen. LAK cell precursors were found to be present in both T11+ and T11- populations, but only in the T3- cell fraction. The generation of LAK activity in highly purified T3- populations of PBL was not accompanied by expression of T3 antigen during a 5-day culture period. LAK activity was next analyzed at the level of limiting dilution clonal microcultures. T11+T3- and T11+T3+ cells, cloned under optimal culture conditions, gave a frequency of proliferating cells of approximately 1 cell in 1.25 for T11+T3+ and 1 cell in 10 for T11+T3- cells. Clones were screened for their ability to lyse fresh ovarian carcinoma cells and K562 target cells. The majority of LAK clones were derived from the T11+T3- cells; moreover, most of the clones derived from these cells displayed LAK activity. Clones displaying LAK activity lysed a panel of fresh or cultured tumor target cells, but failed to lyse PHA-activated lymphoblasts. Surface marker analysis indicated that all the clones had maintained the original T11/T3 phenotype. Whereas 2 T3+ selected LAK clones expressed the T8+T4- phenotype, only 1 out of 9 T3- clones was T8+T4-, all the others lacking both T4 and T8 antigens.

Antigens, Differentiation, T-Lymphocyte↗

PubMed1987

Transmembrane signalling via the T11-dependent pathway of human T cell activation. Evidence for the involvement of 1,2-diacylglycerol and inositol phosphates.

It has previously been shown that some anti-T11 monoclonal antibodies, when used in combination, can activate the human T cell line Jurkat to produce interleukin 2. In this study, we investigate the mechanism by which perturbation of different epitopes of T11 molecules induces activation in Jurkat cells. We show that this activation is initiated by a T11-mediated increase in the concentration of free cytoplasmic calcium ions ([Ca2+]i). The initial increment in [Ca2+]i can occur when extracellular Ca2+ is depleted by EGTA, indicating that Ca2+ from intracellular stores is mobilized. As an early response to extracellular signals provokes a rapid breakdown of a class of lipid known collectively as the phosphoinositides, we measured the levels of phosphatidylinositol bisphosphate (PIP2) which is hydrolyzed to generate inositol triphosphates (IP3), the putative mobilizer of Ca2+ from internal stores and 1,2-diacylglycerol (DAG), the physiological activator of protein kinase C. Monoclonal antibodies directed either against different epitopes of T11 molecules or the T3-Ti antigen receptor complex provoke a rapid breakdown of PIP2, the parental product from which IP3 and DAG derive. In addition antibodies to either the T11 molecules or T3-Ti antigen receptor complex induce marked elevations in IP3, other inositol phosphate compounds and DAG. Taken together, these data indicate that, during T cell activation, due to the perturbation of T11 molecules or T3-Ti antigen receptor complex, membrane phosphoinositides are specifically hydrolyzed. This hydrolysis of phosphoinositides generates two putative second messengers such as IP3 and DAG, which mobilizes Ca2+ from intracellular stores and stimulates protein phosphorylation, respectively.

Antibodies, Monoclonal↗

PubMed1987

CD3+ WT31- peripheral T lymphocytes lack T44 (CD28), a surface molecule involved in activation of T cells bearing the alpha/beta heterodimer.

We have applied two-color fluorescence cytofluorometric techniques to the analysis of the distribution of T44 and CD3 antigens in peripheral blood human lymphocytes. While most CD3+ cells co-expressed T44 antigen, a small distinct subset was CD3+ T44- (2-10% of CD3+ cells). This cell subset also did not react with the WT31 monoclonal antibody (mAb), specific for an alpha/beta framework determinant of the T cell receptor (TCR). Lack of T44 antigen expression was also observed in purified CD3+ WT31- polyclonal populations that had been cultured in medium containing interleukin 2 (IL2) and as well as greater than 30 clones expressing the CD3+4-8-WT31- surface phenotype. Immunoprecipitation experiments confirmed that expression of T44 molecules was confined to CD3+ WT31+ peripheral blood T cells. While conventional CD3+ WT31+ cells produced IL2 in response to mAb directed to CD2, CD3 or T44 surface molecules, CD3+ WT31- cells did not respond to anti-T44 mAb but released IL2 following stimulation with anti-CD2 or anti-CD3 mAb. Therefore, assuming that anti-T44 mimicks the effect of a still undefined natural ligand our data suggest that T cells expressing the gamma-gene surface product may be signalled by stimuli which differ, at least in part, from those acting on CD3+ WT31+ T lymphocytes.

Antigens, Differentiation, T-Lymphocyte↗

PubMed1987

Identification of a novel 45-kDa cell surface molecule involved in activation of the human Jurkat T cell line.

This report describes a surface molecule, Tp45, which appears to be involved in interleukin 2 production and Ca2+ mobilization by Jurkat cells. The Tp45 molecule was identified by a monoclonal antibody, MX13, on the surface of either T3/TCR+ or T3/TCR- human T cell lines. Biochemical data showed that mAb MX13 precipitated a single polypeptide chain of 45 kDa both under reduced and nonreduced conditions from lysates of 125I-surface-labeled cells. Sequential immunodepletion experiments using lysates of 125I-labeled T3/TCR+ cells showed that Tp45 was distinct from the alpha chain of the TCR complex. However, incubation of such cells with either anti-T3 or anti-TCR monoclonal antibody induced complete modulation of both the T3/TCR complex and Tp45. Conversely, complete modulation of both Tp45 and the T3/TCR complex was observed after incubation with anti-Tp45 antibody. Functional studies showed that anti-Tp45 antibody induced high levels of interleukin 2 production in Jurkat cells. In addition, incubation of these cells with the antibody resulted in Ca2+ mobilization from internal stores. Anti-Tp45 antibody reacted with 3-19% peripheral blood (E-rosette-positive) T cells in individual donors. The magnitude of the proliferative response elicited by anti-Tp45 antibody for peripheral blood T cells was lower than that induced by an anti-T3 antibody. This observation is compatible with the idea that only a subpopulation of T cells is reactive with anti-Tp45. Multicolor flow cytometry analysis showed that the Tp45+ cells belong preferentially to the T8 subset.

Animals↗

PubMed1987

Selection and characterization of T-cell variants lacking molecules involved in T-cell activation (T3 T-cell receptor, T44, and T11): analysis of the functional relationship among different pathways of activation.

A clone of the interleukin 2-producing Jurkat leukemia cell line termed JA3 (surface phenotype, T3+, Ti+, T44+, T11+, T40+) has been used to induce and select cell variants lacking surface molecules involved in T-cell activation. Following 200 rad of gamma-radiation (1 rad = 0.01 Gy), cells were treated with monoclonal antibodies (mAbs) directed to T3, Ti, T44, or T11 antigen and complement. After growth of the residual cells in culture, "negative" cells were cloned under limiting conditions. Depending on the specificity of the mAb used for the immunoselection, three groups of variants were obtained. (i) The use of mAbs directed to T3 or Ti resulted in cell variants that expressed the T3 Ti- T44+ Leu1+ T11+ T40+ 4F2+ HLA class I+ surface phenotype. (ii) Immunoselection with anti-T44 mAb resulted in 2 variants that shared the T3- Ti- T44- Leu1- T11+ T40+ 4F2+ HLA class I+ phenotype. (iii) Cell treatment with anti-T11 mAb resulted in 15 variants characterized by the lack of T11 antigen expression and of all the other T-cell-specific surface antigens. Therefore, it appears that the different sets of JA3 cell variants, like T cells at discrete stages of intrathymic differentiation, may follow a coordinated expression of surface differentiation antigens. Analysis of the functional responsiveness of the three distinct groups of JA3 cell variants to different stimuli showed that all produced interleukin 2 in response to A23187 calcium ionophore plus phorbol 12-myristate 13-acetate. The first group of variants (T3- Ti-) did not respond to stimulation with anti-T3, anti-Ti, or anti-T44 mAbs. Eight of 9 did not respond to phytohemagglutinin either; however, all responded to appropriate stimulatory combinations of anti-T11 mAbs (and to calcium ionophore). The second group of variants (T3-, Ti-, T44-, T11+), similar to the first group, did not respond to anti-T3, anti-Ti, anti-T44 mAbs, and phytohemagglutinin, but they were fully responsive to anti-T11 mAb. The last group of variants (lacking all the T-cell-specific surface antigens) only responded to calcium ionophore A23187.

Antibodies, Monoclonal↗

PubMed1986

Modulation of surface T11 molecules induced by monoclonal antibodies: analysis of the functional relationship between antigen-dependent and antigen-independent pathways of human T cell activation.

Previous data indicated that T lymphocyte activation can be achieved by using a combination of anti-T11 monoclonal antibodies (mAb) directed to the "T11(2)" and the "T11(3)" epitopes, respectively. Unlike the T cell activation induced by antibodies directed to the T3-T cell receptor (Ti) complex or to T44 molecules, the anti-T11 mAb-induced cell activation was not accompanied by surface modulation of the T11 antigen. In the present study we show that appropriate stimulatory combinations of anti-T11 mAb are able to induce T11 antigen modulation in a variety of T cells including polyclonal peripheral blood populations, normal as well as leukemic (JA3) T cell clones. The first anti-T11 mAb combination leading to both cell activation and T11 antigen modulation was given by a mAb directed to the T11(2) epitope and by another mAb recognizing an epitope belonging to the T11(1) group. The second combination was given by two mAb directed against two different determinants of the T11(1) group. The ability to induce T11 antigen modulation allowed a more precise analysis of the pathway of T cell activation initiated by T11 molecules and its physical and functional relationship with the other known pathways of T cell activation. T cells following T11 antigen modulation failed to respond to subsequent stimulation with anti-T11 mAb. The refractory period lasted for 48-72 h and the restoration of the responsiveness to anti-T11 mAb coincided with the re-expression of T11 molecules at the cell surface. Modulation of T11 antigen did not affect the surface expression of T3, Ti or T44 molecules, in addition, "modulated" cells maintained their ability to respond to mAb directed against T3, Ti or T44 molecules. On the contrary, antibody-induced modulation of the T3-Ti receptor complex abrogated both T11- and T44-dependent T cell activation. Finally, antibody-induced modulation of T44 antigen did not inhibit either the T11- or the T3-Ti-dependent pathway of T cell activation. These data indicate that down-regulation of the pathway of T cell activation initiated by T11 molecules can be induced not only by modulation of the antigen receptor complex but also by appropriate mAb to T11 molecules and, presumably, by the natural ligand binding to T11 molecules.

Antibodies, Monoclonal↗

PubMed1986

Signal transducing mechanisms involved in human T cell activation via surface T44 molecules. Comparison with signals transduced via the T cell receptor complex.

Antibodies against the T44 surface molecule have been shown to activate human T cells to produce interleukin 2. The role of Ca2+ in the triggering of the interleukin 2-producing Jurkat T cell line by anti-T44 monoclonal antibody has been investigated. We show that activation is initiated by an increase in the concentration of free cytoplasmic calcium ions [Ca2+]i. Subsequently, we have investigated the mechanism by which perturbation of T44 molecules induces increases of [Ca2+]i in Jurkat cells. We show that the anti-T44-mediated increase in [Ca2+]i can occur only in presence of extracellular Ca2+, since no increment is detectable when extracellular Ca2+ is depleted by EGTA. Thus, it appears that perturbation of T44 molecules, unlike that of T3-Ti antigen receptor complex, fails to mobilize Ca2+ from intracellular stores. As inositol triphosphate is considered the putative mobilizer of Ca2+ from internal stores, we measured the levels of inositol triphosphate and of the other inositol phosphate compounds in Jurkat cells after stimulation with anti-T44 antibodies. In contrast to the stimulation via the T3-Ti antigen receptor complex, stimulation via T44 molecule does not induce increments of all three inositol phosphates. Taken together, these data indicate that stimulation mediated by the T44 molecule proceeds via a mechanism independent from the typical inositol lipid metabolism which does not involve mobilization of Ca2+ from internal stores.

Antibodies, Monoclonal↗

PubMed1985

Anticlonotypic monoclonal antibodies induce proliferation of clonotype-positive T cells in peripheral blood human T lymphocytes. Evidence for a phenotypic (T4/T8) heterogeneity of the clonotype-positive proliferating cells.

Three previously selected monoclonal antibodies (mAb) directed against the clonotypic structure of a variant (termed JA3) of the interleukin 2 (IL-2)-producing Jurkat leukemia cell line (anti-JTi1-3 mAb) were found to induce an adherent cell-dependent proliferation of peripheral blood T cells in 20 different donors. Unlike the early cell proliferation induced by anti-T3 mAb, anti-JTi mAb-induced proliferation was detectable at day 5-6 of culture and reached peak levels at day 7-9. Less than 1% JTi+ cells were consistently detected in the starting peripheral blood lymphocytes or in control cultures in which cells were stimulated with anti-T3, phytohemagglutinin, or allogeneic cells. However, JTi+ cells were found in increasing proportions after culture with anti-JTi mAb and they were mostly represented by large blast cells expressing either the T4 or the T8 antigen, together with typical activation antigens including HLA-DR, IL-2 receptor, and 4F2. Immunoprecipitation experiments and sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that anti-JTi-reactive molecules present on antibody-stimulated lymphocytes or on JA3 cells were similar, disulphide-linked heterodimeric structures.

Animals↗

PubMed1985

Involvement of T44 molecules in an antigen-independent pathway of T cell activation. Analysis of the correlations to the T cell antigen-receptor complex.

Prior studies indicate that the 9.3 monoclonal antibody (mAb) which defines a 44 kD T lineage-specific glycoprotein (T44) enhances the proliferative response of peripheral blood T lymphocytes to phytohemagglutinin (PHA) or allogeneic cells. The T44 molecule was expressed in both resting and activated T lymphocytes and in a subset of thymocytes, as assessed by indirect immunofluorescence and flow cytofluorometry. In view of the potential importance of T44 in T cell activation, we investigated the ability of the 9.3 (anti-T44) antibody to stimulate peripheral blood T lymphocytes under culture conditions giving optimal proliferative responses to anti-T3 mAb. Like UCHT1 (anti-T3) mAb, the 9.3 (anti-T44 mAb) promoted strong proliferative responses of purified T cells, provided that adherent cells were added to the culture. Maximal proliferation in response to 9.3 antibody was consistently detected at day 5 (at day 3 with anti-T3 or PHA). Moreover, triggering of T lymphocytes with 9.3 antibody (in the presence of adherent cells) resulted in strong IL-2 production that peaked at 48 h. Analysis of the physical and functional relationship between the T44 molecule and other molecules involved in T cell activation, including the clonotypically restricted Ti and the monomorphic T3 or T11 molecules, was carried out on a mutagenized jurkat T leukemia cell line. This mutant, termed JA3 (surface phenotype: T11+, T3+, 3A1+, T4-, T8-, DR-, Tac-, 4F2+, T44+) produced large amounts of IL-2 upon stimulation with PHA, anti-T3, or anticlonotypic mAb in conjunction with phorbol myristate acetate (or adherent cells). The molecules precipitated by anti-T44 mAb from 125I-labeled JA3 cells appeared as a diffuse band of Mr 40-45,000 under reducing conditions; under nonreducing conditions, a prominent band of Mr 80-85,000 was observed, while the Mr 40-45,000 band was greatly reduced. Thus, T44 molecules in both reducing and nonreducing conditions had relative molecular weights similar to that of molecules carrying clonotypic (Ti) determinants. In addition, like anti-Ti or anti-T3 mAb, anti-T44 antibody induced JA3 cells to produce large amounts of IL-2 in the presence of phorbol myristate acetate. Other similarities between T44 and molecules carrying clonotypic structures included the susceptibility to antibody-induced modulation and the late reexpression (72 h) at the cell surface after modulation. Taken together, these experiments suggest that anti-T44 mAb might recognize a monomorphic determinant of the T cell receptor molecule or be physically or functionally linked to the T3-Ti complex.(ABSTRACT TRUNCATED AT 400 WORDS)

Antibodies, Monoclonal↗

PubMed1985

Selection and characterization of monoclonal antibodies to the idiotype-like structure of an interleukin-2-producing human leukemia T-cell line.

A variant of the Jurkat leukemia cell line termed JA3 (surface phenotype: T11+., T3+, T4-, T8-, T6-, T1+, 3A1+, HLA-DR-, Tac-, 4F2+) has been used for mouse immunization and production of monoclonal antibodies (MAbs) to molecules carrying clonotypic determinants that are thought to serve as receptor for antigen on human T cells. JA3 had been selected because of its ability to release large amounts of IL-2 following stimulation with phytohemagglutinin (PHA) or anti-T3 antibody in the presence of phorbolmyristate acetate (PMA). This functional property has been exploited for screening of MAbs potentially directed to idiotype-like structures of JA3 cells. Thus supernatants of hybridomas (obtained by fusing mouse splenocytes with P3-UI myeloma cells) were analyzed for their ability to induce JA3 cells to release IL-2 in the presence of PMA. Four stimulatory antibodies reacted with JA3 but not with polyclonal T-cell populations, T-cell clones, or T and B tumor cell lines as assessed by indirect immunofluorescence and fluorescence-activated cell sorter (FACS) analysis. All 4 antibodies immunoprecipitated the same disulphide-linked heterodimeric molecules having a molecular mass (Mr) of approximately 85,000 under non-reducing conditions that was resolved in 2 major peptides of 40,000 and 45,000 under reducing conditions. These data indicate that these antibodies (termed anti-JTi) were directed to the clonotypic-restricted structures of the JA3 T-cell-receptor molecules. Unlike the anticlonotypic antibodies described so far, anti-JTi MAbs were capable of triggering IL-2 production even in unbound, soluble form, in the absence of adherent cells or PMA. Competitive inhibition experiments, in which 35S-labelled anti-JTi MAbs have been used, provided evidence that they may be directed against different epitopes on the same clonotypic structure.

Antibodies, Monoclonal↗

PubMed1985

Involvement of T3 and T8 molecules in human T cell receptor function. Anti-T3 or anti-T8 antibodies do not block the antigen-dependent activation of a subset of alloreactive cytolytic T cell precursors.

In the present study, we have analyzed the effects of anti-T8 and anti-T3 monoclonal antibodies (mAb) on the generation of human allospecific cytolytic T lymphocytes (CTL). A sensitive limiting dilution microculture system, in which graded numbers of responder T cells were added to 10(5) irradiated allogeneic spleen cells and saturating amounts of exogeneous interleukin 2, has been employed to provide minimal estimates of the frequencies of alloreactive CTL precursors (CTL-P) present in T lymphocyte populations freshly isolated from peripheral blood. Addition of anti-T8 or anti-T3 mAb at the onset of micro mixed lymphocyte culture containing peripheral blood T lymphocytes as responding cells caused a 65-80% reduction in the frequency of specific CTL-P which proliferate under these conditions. Moreover, in most instances (greater than 80%) the cytolytic activity of those CTL-P which underwent clonal expansion in the presence of either anti-T8 or anti-T3 mAb was found to be resistant to inhibition by the corresponding mAb added during the cytolytic assay. In addition, a great degree of overlap existed between microcultures resistant to anti-T3 and those resistant to anti-T8 mAb. In contrast, neither antibody had any inhibitory effect when added later to the cultures, presumably because at this stage CTL-P had been already triggered by alloantigens. Taken together our data indicate that the heterogeneity in the susceptibility to inhibition by anti-T3 or anti-T8 mAb, previously observed at the level of CTL clones, is predetermined already at the level of peripheral blood CTL-P.

Antibodies, Monoclonal↗

PubMed1985

Involvement of T11 molecules in antigen receptor-mediated T lymphocyte functions: effect of anti-T11 monoclonal antibody on functional capabilities of alloreactive T cell clones.

As shown by previous studies, the sheep erythrocyte-binding T11 molecule is involved in T cell activation, as well as in mechanisms of specific allogeneic target cell lysis. In this study, we utilized two anti-T11 monoclonal antibodies (mAb) that inhibited the specific cytolytic activity of mixed lymphocyte culture (MLC)-activated T cells to analyze, at the clonal level, the involvement of T11 molecules in (a) antigen-specific vs. nonspecific mechanisms of target cell lysis, and (b) antigen-driven T cell proliferation and interleukin 2 (IL 2) production vs. IL 2-induced cell proliferation. In contrast to anti-T3 or anti-T8 mAb, antibodies to T11 molecules inhibited the cytolytic activity of MLC-derived allospecific clones in a uniform manner. In addition, anti-T11 antibodies inhibited the specific activity of cytotoxic T lymphocyte clones resistant to anti-T3 antibodies, even after antibody-induced modulation of T3 molecules (while anti-T3 mAb had no effect). Similarly, anti-T11 antibodies inhibited the alloantigen-induced proliferation and IL 2 release of alloreactive clones independent of their T4+ or T8+ phenotype. The inhibitory activity of anti-T11 antibodies appears to be confined to antigen-specific T cell functions since neither natural killer-like activity of cytotoxic T lymphocyte clones nor the IL 2-induced clonal proliferation was affected. Thus, our results indicate that T11 molecules are functionally involved in antigen recognition by T cell regardless of their function and T4/T8 phenotype. The possible mechanisms of anti-T11 antibody-mediated inhibition are discussed.

Antibodies, Monoclonal↗

PubMed1985

Clonal analysis of the involvement of T11 molecules in antigen receptor-mediated T lymphocyte functions.

In this study, we utilized two anti-T11 monoclonal antibodies (mAbs) that inhibited the specific cytolytic activity of mixed lymphocyte culture (MLC) activated T cells to analyze, at the clonal level, the involvement of T11 molecules in 1) antigen specific versus non-specific mechanisms of target cell lysis 2) antigen-driven T cell proliferation and IL-2 production versus IL-2-induced cell proliferation. In contrast to anti-T3 or anti-T8 mAbs, antibodies to T11 molecules inhibited the cytolytic activity of MLC-derived allospecific clones in a uniform manner. In addition, anti-T11 antibodies inhibited the specific activity of CTL clones resistant to anti-T3 antibodies, even after antibody-induced modulation of T3 molecules (while anti-T3 mAbs had no effect). Similarly, anti-T11 antibodies inhibited the alloantigen induced proliferation and IL-2 release of alloreactive clones independent on their T4+ or T8+ phenotype. The inhibitory activity of anti-T11 antibodies appears to be confined to antigen-specific T cell functions since neither natural killer-like activity of CTL clones nor the IL-2 induced clonal proliferation was affected. Thus, our results indicate that T11 molecules are functionally involved in antigen recognition by T cell regardless of their function and T4/T8 phenotype.

Antibodies, Monoclonal↗

PubMed1985

Phenotypic and functional heterogeneity of human peripheral blood T lymphocytes producing colony stimulating factor. A clonal and precursor frequency analysis.

In this report we describe the precursor frequency and the subset distribution of peripheral blood human T cells producing lymphokine(s) acting on the proliferation and differentiation of bone marrow precursors of the granulocyte/macrophage series, as assessed in a liquid microculture assay. Because the sensitivity of this system was similar to that of the classic colony formation assay in semi-solid (methylcellulose) medium, it is likely that the lymphokine activity measured in this assay corresponds to the colony-stimulating factor (CSF) activity. Single human T lymphocytes, isolated from peripheral blood by E rosetting and Ficoll-Hypaque gradients, were seeded into microculture wells by limiting dilution or micromanipulation techniques and were incubated under culture conditions that allow clonal expansion of essentially all T cells. After 15 to 20 days, microcultures were stimulated with PHA and CSF activity was assayed in culture supernatants 24 hr thereafter. About 45% (1/2.3) of peripheral blood T cells were found to give rise to CSF-producing progenies. Moreover, when fluorescence-activated cell sorter-purified T4+ and T4- (or T8- and T8+) were analyzed, the frequency of the precursors of CSF-producing cells was 1/1.5 in the T4+ subset, whereas approximately one-third of the T8+ cells had this functional potential. To additionally characterize T cells responsible for CSF production, unfractionated T cells as well as T4+ and T4- cells were cloned by single cell micromanipulation. The resulting clones were analyzed simultaneously for the production of IL 2, production of CSF and for cytolytic activity in a lectin-dependent assay. It was found that 25/48 clones obtained from unfractionated T cells produced CSF, whereas 23/48 and 19/48 produced IL 2 or had cytolytic activity respectively. Six of the 25 CSF-producing clones had only this functional capability, whereas the remaining clones in addition displayed cytolytic activity (4/25), IL 2 production (10/25), or both (5/25). A similar functional heterogeneity was observed among T4+ and T4- clones, thus indicating that T cells producing CSF are functionally heterogeneous within both the T4+ and T8+ subsets.

Cell Differentiation↗

PubMed1984

Clonal heterogeneity in the requirement for T3, T4, and T8 molecules in human cytolytic T lymphocyte function.

In an attempt to define the requirement of T8, T4, and T3 surface molecules in functional interactions occurring between human cytolytic T lymphocytes (CTL) and specific target cells, we have analyzed a large number of CTL clones derived from primary mixed lymphocyte culture (MLC) T cell populations for their susceptibility to inhibition by monoclonal antibodies (mAb) directed against these surface antigens. In most experiments, MLC T cells were stained with B9.4 (anti-T8) or OKT4 (anti-T4) mAb, separated into positive and negative cells using a fluorescence-activated cell sorter (FACS) and cloned under limiting conditions. While the lytic activity of the majority of T8+ CTL clones was inhibited by B9.4 mAb, approximately 15% of these clones were unaffected even in the presence of excess antibody. Flow cytofluorometric analysis of T8 antigen in individual clones did not show any correlation between the amount of T8 antigen expressed, the magnitude of cytolytic activity and the susceptibility (or lack thereof) to inhibition by B9.4 mAb. Of the 16 T4+ CTL clones analyzed, 7 were resistant to inhibition by OKT4 mAb even at doses 10-fold higher than that sufficient for complete inhibition of susceptible clones. Again, no correlation was found between the amount of T4 antigen expressed and the susceptibility to inhibition by the corresponding antibody. The same sets of T8+ and T4+ CTL clones were also analyzed for their susceptibility to inhibition by OKT3 mAb. Although all of the clones expressed the T3 surface antigen, only 15/23 T8+ clones and 9/14 T4+ clones were inhibited by anti-T3 mAb. To further document this clonal heterogeneity, we selected two T3+ T4- T8+ CTL clones that had no concomitant NK-like activity. One clone was resistant to inhibition by OKT3 mAb, whereas the other was highly susceptible. Incubation with OKT3 mAb resulted in modulation of the T3 molecules in both clones. Following modulation, however, the cytolytic activity of the resistant clones was unaffected, whereas the lytic activity of the susceptible clone was abrogated. These results thus indicate extensive clonal heterogeneity in the requirement for T3, T4, and T8 molecules in CTL function. Moreover, it appears that T3 molecules are not always physically and functionally linked to CTL receptor structures.

Antibodies, Monoclonal↗

PubMed1984

Assignment of human natural killer (NK)-like cells to the T cell lineage. Single allospecific T cell clones lyse specific or NK-sensitive target cells via distinct recognition structures.

The aim of the present study was to define the cell lineage of mixed lymphocyte culture (MLC)-induced natural killer (NK) effector cells. Human MLC cells were plated under limiting microculture conditions in the presence of irradiated spleen cells and interleukin 2-containing supernatant. After 18 days, microcultures were scored for proliferation and for cytolytic activity against specific lymphoblasts and NK-sensitive K562 target cells. About 1 in 7 and 1 in 5 proliferating microcultures had specific or NK-like cytolytic activity, respectively. Moreover, several microcultures exhibited dual (specific and NK-like) cytolytic activity, even when they had been established at relatively low numbers of responding cells/well (0.5-0.25) to ensure a high probability of monoclonality. Direct evidence for the existence of cytolytic effector cells with dual activity was achieved by using clones derived from single MLC T cells by micromanipulation. Out of 26 cytolytic clones so derived, 16 exhibited specific cytolytic activity, whereas 22 lysed K562 target cells. More interestingly, 12 of these 26 clones were active against both types of target cells. Only one of these clones was able to lyse autologous or unrelated target cells. In contrast, all such clones lysed the NK-sensitive cell lines G11, MOLT-4, Raji, Daudi, Chang and T-24. Addition of saturating amounts of B9-4 monoclonal antibody in the lytic assays resulted in the inhibition of the specific cytolysis, but not the NK-like activity of clones with dual cytolytic activity. It thus appears that (a) alloreactive cytotoxic T lymphocytes can mediate both specific and NK-like cytolysis and (b) two independent recognition structures are involved in this dual activity.

Cell Differentiation↗

PubMed1984

Frequent coexpression of cytolytic activity and lymphokine production among human T lymphocytes. Production of B cell growth factor and interleukin 2 by T8+ and T4+ cytolytic clones.

These studies were designed to determine the degree of overlapping between cytolytic function and lymphokine production among peripheral blood human T lymphocytes. T8+ and T4+ cells were obtained by sorting purified T cells using the fluorescence-activated cell sorter (FACS) and cloned at 0.25 cells/well in a microculture system that allows clonal growth of every T cell. 49/49 T8+ clones but only 5/102 T4+ clones displayed cytolytic activity, as assessed by a lectin-dependent assay. Cytolytic clones were further analyzed for their ability to release interleukin 2 (IL2) and B cell growth factor(s) (BCGF) upon 24 h stimulation with phytohemagglutinin. Fifteen percent and 18% of T8+ cytolytic clones were producing IL2 and BCGF, respectively; in addition 3 out of 5 T4+ cytolytic clones released both lymphokines. Although the majority of cytolytic clones producing IL2 were also producing BCGF, 5 clones released either BCGF or IL2. The present studies indicate that the coexpression of cytolytic and helper/inducer functions is relatively common among peripheral blood T lymphocytes, irrespective of their T8+ or T4+ phenotype.

B-Lymphocytes↗