Biomedical subjects

M S Sy

Publications and source records attributed to M S Sy.

At least 73 records · Page 4Linked to original sources

PubMed1994

Trinitrophenol reactive T-cell hybridomas recognize antigens that require antigen processing.

Protein antigens must be taken up, processed, and displayed on the surface of antigen-presenting cells in association with major histocompatibility complex molecules before they can be recognized by T cells. Whether recognition of the haptens used to study allergic contact hypersensitivity in murine models similarly requires processing has not been determined. We analyzed whether presentation of trinitrophenol to trinitrophenol reactive T-cell hybridomas requires antigen processing by studying the effects of inhibitors of antigen processing and presentation on the ability of a syngeneic B-cell tumor (A20) to present trinitrophenol to a series of interleukin-2 producing, trinitrophenol specific, major histocompatibility complex class II-restricted T-cell hybridomas. The ability of trinitrophenol modified A20 cells to stimulate the hybridomas was completely inhibited by monoclonal, anti-trinitrophenol, or anti-Ia antibodies and was significantly reduced by paraformaldehyde fixation immediately after trinitrophenol modification. Trinitrophenol-modified A20 cultured at 37 degrees C for 2 h prior to fixation was significantly more effective at stimulating the hybridomas than trinitrophenol-modified A20 fixed immediately. The ability of A20 to present trinitrophenol was inhibited by chloroquine. Paraformaldehyde fixation and chloroquine treatment had similar effects on the ability of trinitrophenol modified lymph node dendritic cells to stimulate the trinitrophenol specific hybridomas. Paraformaldehyde fixation and chloroquine treatment had similar effects on the ability of A20 cells to present ovalbumin to ovalbumin-specific hybridomas as they had on the ability of trinitrophenol modified A20 cells to present trinitrophenol to the trinitrophenol specific hybridomas. One of seven T-cell hybridomas responded to trinitrophenol modified ovalbumin but not other trinitrophenol modified proteins. These results suggest that, at least in part, T cells in the contact hypersensitivity response to trinitrophenol recognize antigens that require processing and that trinitrophenol modified proteins can be recognized.

Albumins↗

PubMed1993

Antibodies to intercellular adhesion molecule 1/lymphocyte function-associated antigen 1 prevent crescent formation in rat autoimmune glomerulonephritis.

In patients with glomerulonephritis widespread crescents are associated with a poor prognosis. Crescent formation appears to depend on the migration of mononuclear cells into Bowman's space, and therefore the interaction between leukocytes and glomerular endothelium may be a critical event in the genesis of crescents. We performed the present study to determine the effects of mouse monoclonal antibodies to the adhesion molecules intercellular adhesion molecule 1 (ICAM-1) and lymphocyte function-associated antigen 1 (LFA-1) in a model of crescentic glomerulonephritis in Wistar-Kyoto rats, induced by immunization with bovine glomerular basement membrane (GBM). By 10-14 d after immunization, the rats had developed circulating anti-GBM antibodies, reactive with the alpha 3 chain of type IV collagen (the Goodpasture antigen), accompanied by proteinuria, accumulation of rat immunoglobulin (Ig)G in the GBM, increased expression of ICAM-1 by glomerular endothelial cells, infiltration of glomerular tufts with LFA-1+ T cells and monocyte/macrophages, and early crescents. At 5 wk all rats had diffuse fibrocellular crescents, glomerular sclerosis, and tubulointerstitial damage. All rats developed severe renal insufficiency and died by 5 or 6 wk. The administration of monoclonal antibodies to rat ICAM-1 and LFA-1 markedly decreased the severity of the renal disease. In a group of rats injected three times a week with the monoclonal antibodies, from 2 d before immunization with GBM to day 14, glomerular abnormalities and proteinuria were virtually absent at day 14; even at 5 wk glomerular disease was quite mild, with only slight crescent formation and with only a mild decrease in renal function. When treatment was continued until 5 wk, the beneficial effects were even more marked, with virtual absence of crescents and with preservation of normal renal function. In a group of rats in which treatment was initiated on day 14, shortly after the appearance of glomerular abnormalities, progression of the disease was appreciably retarded, and the decrease in renal function was inhibited. The kidneys of rats treated from days -2 to 14 with antibodies to ICAM-1 and LFA-1 showed bright linear staining for rat IgG along the GBM, which did not differ in intensity from that seen in untreated rats. Furthermore, the titers of anti-GBM antibodies at 2 wk in treated rats were not lower than that seen in most of the untreated rats. There was, however, moderate reduction of anti-GBM antibodies at 5 wk in the treated rats.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1993

Anti-CD3:anti-IL-2 receptor bispecific monoclonal antibody. Targeting of activated T cells in vitro.

T cells are major mediators of graft rejection and many autoimmune diseases. During the Ag recognition process, T cells often become activated. We tested the hypothesis that an anti-CD3:anti-CD25 (CD3,25) bispecific mAb (BSMAB) can effectively and selectively target activated T cells. By flow cytometric analysis, the CD3,25 BSMAB was shown to bind avidly to activated T cells that coexpress CD3 and CD25 (p55 chain of the IL-2R), achieving higher levels than the parent anti-CD3 and anti-CD25 mAb. It bound only weakly to unstimulated T cells. The CD3,25 BSMAB effectively redirected CTL to lyse CD25-bearing PHA-stimulated T lymphoblasts and the IL2-dependent CTLL tumor cell line in chromium release assays. It was highly effective in blocking MLR as shown by inhibition of [3H]TdR incorporation. However, the CD3,25 BSMAB has a low potential to activate resting T cells, as it induced only minimal [3H]TdR incorporation even in the presence of exogenous IL-2. In the absence of exogenous IL-2, the CD3,25 BSMAB was unable to induce [3H]TdR incorporation. In contrast, the parent anti-CD3 mAb induced a high degree of incorporation. In summary, the CD3,25 BSMAB selectively targets activated CD25-expressing T cells and lymphomas although maintaining a low activation potential for unstimulated T cells, potentially advantageous properties that can be exploited for immunotherapy.

Animals↗

PubMed1993

Monoclonal anti-CD44 antibody acts in synergy with anti-CD2 but inhibits anti-CD3 or T cell receptor-mediated signaling in murine T cell hybridomas.

We investigated the effects of anti-murine CD44 monoclonal antibodies on the activation of antigen-specific T cell hybridomas. Anti-murine CD44 antibodies by themselves did not induce the production of IL-2 by antigen-specific T cell hybridomas. However, anti-murine CD44 monoclonal antibodies were able to either inhibit or enhance the production of IL-2, depending on the other monoclonal antibodies used as comitogenic stimuli. When a T cell hybridoma was activated by antigen and antigen-presenting cells or anti-CD3 antibodies, addition of anti-CD44 antibodies inhibited IL-2 production. In contrast, monoclonal anti-CD44 antibodies acted in synergy with anti-human CD2 antibodies in stimulating a murine T cell hybridoma stably transfected with the human CD2 gene to produce IL-2. Therefore, cross-linking of surface CD44 is able to deliver either a positive or a negative signal in murine antigen-specific T cell hybridomas. One of the ligands for CD44 is hyaluronic acid. Hyaluronic acid in vitro significantly increased the activation of murine T cell hybridomas. Hyaluronic acid itself was mitogenic for T cell hybridomas. Therefore, in addition to being an adhesion molecule, CD44 functions as a signal-transducing molecule on murine T cell hybridomas.

Animals↗

PubMed1992

Inhibition of tumor growth in vivo with a soluble CD44-immunoglobulin fusion protein.

CD44H is the principal cell surface receptor for hyaluronate, which is a major glycosaminoglycan of the extracellular matrix. Expression of CD44H is enhanced in a variety of malignant tumors and correlates with tumor aggressiveness, supporting the notion that interaction between CD44H and hyaluronate may play an important role in tumor growth and dissemination. In this report we show that in vivo tumor formation by human lymphoma Namalwa cells, stably transfected with CD44H, can be suppressed by a soluble human CD44H-immunoglobulin fusion protein. Disruption of the interaction between CD44H and its physiologic ligands may provide a novel strategy for controlling tumor growth in vivo.

Animals↗

PubMed1991

Distinct effects of two CD44 isoforms on tumor growth in vivo.

Tumor growth is dependent in part on interactions between tumor cells and the extracellular matrix of host tissues. Expression of the cell surface glycoprotein CD44/Pgp-1, which mediates cell-substrate interactions is increased in many types of malignancies, but the role of CD44 in tumor growth is largely undefined. Recently, two isoforms of CD44 have been identified: an 80-90 kD form, which has high affinity for cell bound hyaluronate and a 150 kD form which does not mediate attachment to hyaluronate-coated surfaces. In this work, human B cell lymphoma cells stably transfected with cDNA clones encoding either of the two CD44 isoforms were compared for tumorigenicity and metastatic potential in nude mice. Expression of the 80-90 kD form but not the 150 kD form of CD44 greatly enhanced both local tumor formation and metastatic proclivity of the lymphoma cells. Our results suggest that CD44 polypeptides may play an important role in regulating primary and metastatic tumor development in vivo.

Animals↗

PubMed1991

The B lymphocyte adhesion molecule CD22 interacts with leukocyte common antigen CD45RO on T cells and alpha 2-6 sialyltransferase, CD75, on B cells.

Functional maturation of B lymphocytes correlates with expression of the B lineage-specific cell surface glycoprotein CD22. Two CD22 polypeptides have been characterized and suggested to play a role in B cell-B cell interaction as well as in B cell adhesion to monocytes. In this work we provide evidence that CD22 is directly involved in the cognate interaction between B and T cells. One of the two CD22 polypeptides, CD22 beta, interacts with a specific ligand on a subpopulation of CD4+ T cells. Our results suggest that the T cell ligand of CD22 is CD45RO, an isoform of the leukocyte common antigen class of phosphotyrosine phosphatases associated with the helper T cell phenotype. We further demonstrate that CD22 recognizes a second ligand, CD75, expressed predominantly on activated B cells and shown to be a cell surface alpha 2-6 sialyltransferase.

Antibodies, Monoclonal↗

PubMed1991

Molecular analysis of the interaction of p56lck with the CD4 and CD8 antigens.

The CD4 and CD8 antigens on the surface of T cells appear to bind to major histocompatibility complex (MHC) class II and I antigens, respectively. These antigens also synergize with the Ti(TcR)/CD3 complex in the potentiation of T-cell proliferation. Our earlier work demonstrated that the CD4 and CD8 receptors are coupled to a protein-tyrosine kinase termed p56lck from normal and transformed T lymphocytes. The p56lck protein is a member of the src family and its homology with receptor-kinases such as the epidermal growth factor receptor (EGFR) make it an important candidate in signal transduction. In this paper, we show in transfectants that p56lck interacts with the cytoplasmic tail of the CD4 antigen. Murine p56lck can interact across species with the human CD4 receptor. Furthermore, peptide competition studies showed that a specific sequence within the cytoplasmic tail of CD4 interacts with the kinase. Cysteine residues also appear to play key roles in this interaction. Lastly, we show biochemically that the CD4:p56lck complex can physically associate with the epsilon chain of the CD3 complex on HPB-ALL transformed T cells. This interaction may provide a bridge by which events related to ligand binding to Ti(TcR)/CD3 may trigger T cells via the CD4/CD8:p56lck complex.

Amino Acid Sequence↗

PubMed1990

Phorbol myristate acetate-induced down-modulation of CD4 is dependent on calmodulin and intracellular calcium.

PMA causes rapid down-modulation of CD4 molecules on murine immature thymocytes, human PBL, and CD4-positive human tumor cell lines, but not on murine peripheral lymphocytes. The mechanisms of phorbol ester-induced down modulation of CD4 molecules, however, have not been elucidated. To determine how PMA down-modulates CD4 expression by T lymphocytes, we studied the ability of inhibitors of protein kinase C, calmodulin, actin, and tubulin to block PMA-induced modulation of CD4 in several murine and human cell types. We also tested the ability of intracellular and extracellular calcium chelators to block CD4 internalization. There was marked variability in the degree of PMA-induced down-modulation of CD4 among various cell types. The effects of PMA on CD4 expression were greater for murine thymocytes, for human PBL, and for the human lymphoblastic leukemia cell line, MOLT-3, than for any of the other cell types studied. The protein kinase C inhibitor, 1-(5-isoquinolinesulfonyl)-2-methylpiperazine, blocked phosphorylation but not internalization of CD4 molecules induced by PMA. Therefore, phosphorylation of CD4 molecules by protein kinase C is not required for the internalization of the molecules. Internalization was blocked by both inhibitors of calmodulin, N-(6-aminohexyl)-5-chloro-1-naphthalene-sulfonamide, and trifluoperazine. PMA-induced internalization of CD4 was blocked by Quin-2 AM, which chelates intracellular calcium. EGTA, which chelates extracellular calcium, did not block internalization. Inhibitors of actin or tubulin did not block internalization. These results suggest that PMA-induced modulation of CD4 can occur in the absence of phosphorylation of the CD4 molecules and is calmodulin and intracellular calcium dependent.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗

PubMed1989

Production of hapten-specific T cell hybridomas and their use to study the effect of ultraviolet B irradiation on the development of contact hypersensitivity.

We produced a series of T cell hybridomas that produce IL-2 when cultured with syngeneic APC coupled to FITC or TNP. These hybridomas are hapten specific and Ia restricted. The hybridomas were used to detect hapten-bearing APC in draining lymph nodes of mice sensitized with trinitrochlorobenzene or FITC in vivo. Hapten-bearing APC capable of stimulating the hybridomas were detectable in draining lymph nodes of hapten-painted mice within 3 h after sensitization. The ability of lymph node APC to stimulate the hybridomas peaked at 24 h and declined by 48 h. The dendritic cell subpopulation was the subpopulation of cells that were found in the regional lymph nodes of hapten-painted animals that were capable of stimulating the hybridomas to produce IL-2. Prior treatment of the skin with low dose UVB irradiation before epicutaneous application of contact sensitizers significantly reduced the capacity of hapten-bearing APC to stimulate the hybridomas. This observation was corroborated by results obtained from flow microfluorometry analysis of lymph node cells from FITC-sensitized mice. Lymph node dendritic cells obtained from FITC-painted mice contain a brightly staining group of cells by flow microfluorometry analysis. Lymph node dendritic cells from FITC-painted, UVB-irradiated mice did not contain this brightly staining population. These results indicate that low dose, local UVB irradiation may affect APC migration and/or function. We believe that these hybridomas will prove to be useful tools in the study of the development and regulation of contact hypersensitivity.

Animals↗

PubMed1989

Defective signal transduction in CD4-CD8- T cells of lpr mice.

Mice homozygous for the lpr gene develop a lymphoproliferative disorder due to expansion of a subset of CD4-CD8- T cells. Triggering of the T-cell receptor in these lpr T cells does not lead to translocation of protein kinase C or phosphorylation of CD3, interleukin-2 production, or proliferation, whereas a combination of phorbol ester and calcium ionophore does. Stimulation with concanavalin A or anti-CD3 induces phosphoinositide hydrolysis. The rise in inositol bisphosphate, inositol triphosphate, and inositol tetrakisphosphate, identified by HPLC, is similar in +/+ and lpr T cells. The concentration of cytoplasmic free calcium ([Ca2+]i), however, under basal and stimulated conditions is significantly lower in lpr T cells. The lower basal [Ca2+]i may explain why induction of proliferation with phorbol ester and calcium ionophore requires a higher concentration of ionophore in these cells than in normal T cells. The lower [Ca2+]i obtained on stimulation may contribute to the activation defect of CD4-CD8- lpr T cells.

Animals↗

PubMed1989

Autoantibody in MRL/Mp-lpr/lpr mice. A monoclonal antibody specific for the abnormal T cells from mice bearing the lpr/lpr gene.

We generated mAb from an unimmunized autoimmune MRL/Mp-lpr/lpr mouse. One of these mAb A108, reacted with cell surface Ag present on abnormal T cells from MRL/Mp-lpr/lpr, C3H-lpr/lpr, and C57BL/6-lpr/lpr mice. We failed to detect significant numbers of A108 bearing cells in the lymph nodes of MRL-Mp/+/+, normal C3H or normal C57BL/6 mice. Therefore, the expression of A108 correlates with the presence of the lpr/lpr gene. A108 binds to a variety of murine T cell tumor lines (e.g., EL4, BW5147, and YAC-1) and human T cell tumor lines (e.g., MOLT-3, Sup T1, and Jurkat). A108 does not bind to normal human PBL. Immunoprecipitation of surface iodinated EL-4 and BW5147 with A108 identified one major protein with a Mr of about 17.5-kDa. The significance of these findings with respect to the development of lymphoid proliferation and autoimmune disease in mice bearing the lpr/lpr gene will be discussed.

Animals↗

PubMed1989

Requirements for modulation of the CD4 molecule in response to phorbol myristate acetate. Role of the cytoplasmic domain.

CD4 (T4) is a 60 kD glycoprotein expressed on a subset of T lymphocytes. CD4 augments T cell responses to suboptimal Ag stimulation. In addition, the CD4 molecule is the receptor for HIV-1. CD4 is phosphorylated on serine residues within the cytoplasmic domain and its cell surface expression is decreased in response to PMA, APC bearing the appropriate Ag or HIV infection. The kinetics of CD4 phosphorylation and modulation are similar, suggesting that the two events may be related. L3T4, the murine CD4 equivalent, is not modulated from the surface of mature, peripheral T cells in response to PMA. The difference in the ability to modulate L3T4 and CD4 in response to PMA may be due to differences between the two molecules or to differences between the cells in which they are expressed. To further define the requirements for CD4 modulation, we used retroviral vectors to transfer the cDNA for CD4 and various mutants of CD4 into two murine T cell hybridomas that express L3T4. One of these hybridomas, By155.16, does not modulate L3T4 in response to PMA and the other, 5D5.63, does modulate L3T4 in response to PMA. When expressed by these hybridomas CD4 is not modulated from the surface of By155.16 and is modulated from the surface of 5D5.63 in response to PMA. In both of these hybridomas, CD4 is phosphorylated on serine residues in response to PMA. A mutant form of CD4, CD4 delta, was constructed in which the majority of the cytoplasmic domain was deleted. When expressed in 5D5.63, CD4 delta was not modulated in response to PMA. Replacing the cytoplasmic domain of CD4 with that of the human IL-2 receptor did not reconstitute the ability of CD4 to be modulated. These results suggest that the inability to modulate L3T4 from the surface of murine peripheral T cells is due to features of the cell and not the molecule. Furthermore, the cytoplasmic domain of CD4 is required for its modulation from the cell surface in response to PMA.

Amino Acid Sequence↗

PubMed1989

Surface expression of CD3 in the absence of T cell receptor (TcR): evidence for sorting of partial TcR/CD3 complexes in a post-endoplasmic reticulum compartment.

The T cell receptor (TcR) for antigen, on the majority of T cells, is a disulfide-linked heterodimer composed of the alpha and beta chains, noncovalently associated with the CD3 complex of polypeptides (gamma, delta, epsilon and zeta). In this report, two murine thymoma cell lines are described which synthesized incomplete TcR/CD3 complexes and expressed low levels of CD3 on their surface in the absence of the TcR chains. The partial TcR/CD3 complexes were composed primarily of the inherently metabolically stable CD3 gamma and epsilon subunits. These results were in contrast to previous studies, which suggested that synthesis of all of the component chains of the TcR/CD3 complex is required for the successful transport of any of the chains to the cell surface. The efficiency of transport of the partial TcR/CD3 complexes from the endoplasmic reticulum (ER) to medial Golgi in the two thymomas was similar to complete complexes. However, the transport of the incomplete receptors was impaired at some point between the medial Golgi and the plasma membrane. Taken together with previous studies, these results suggested that T cells have mechanisms to retain partial TcR/CD3 complexes intracellularly both in the ER and in an undefined post-ER compartment. However, the transport of low levels of partial TcR/CD3 complexes to the cell surface in some T cell lines implied that the retention mechanisms may not always be completely efficient. Cross-linking of the surface, partial TcR/CD3 complexes with anti-CD3 epsilon antibodies did not stimulate interleukin 2 (IL 2) production. It is possible, however, that the partial TcR/CD3 complexes have some function which is unrelated to the stimulation of IL 2 production.

Animals↗

PubMed1988

Autoreactive T cells in MRL/Mpr-lpr/lpr mice. Characterization of the lymphokines produced and analysis of antigen-presenting cells required.

Lymph node cells from 4-wk-old MRL/Mp-lpr/lpr mice, but not from MRL/Mp-+/+ mice, when cultured in vitro for 5 to 7 days, will spontaneously proliferate and produce IL-2. We examined the expression of several cell surface Ag on lymph node cells from MRL/Mp-lpr/lpr mice before and after in vitro culture. There is an increase in the expression of Thy-1, L3T4, IL-2R, T cell activating protein, T cell receptor, and T3 complex on the surface of cultured cells. Cultured cells produced IL-3, IFN-gamma, and small but detectable amounts of IL-1 in addition to IL-2. Gamma irradiation of APC from young MRL/Mp-lpr/lpr mice or treatment of APC with a mAb (J11D) and C, completely abrogated their stimulatory capacity. These experiments suggest that B cells are the predominant APC responsible in the activation of autoreactive T cells in MRL/Mp-lpr/lpr mice. Lymph node cells from C57BL/6-lpr/lpr or C3H-lpr/lpr mice were unable to spontaneously proliferate or produce IL-2. Lymph node cells from (MRL/Mp-lpr/lpr x C57BL/6-lpr/lpr) F1 mice or (C3H-lpr/lpr x MRL/Mp-lpr/lpr) F1 mice did proliferate and produced IL-2 after in vitro culture. Using T cells from these F1 animals and APC from each parental haplotype, we found that APC from MRL/Mp-lpr/lpr mice induced more proliferation and greater amounts of IL-2, when compared to APC from F1 animals. APC from C57BL6-lpr/lpr mice or C3H-lpr/lpr were unable to induce spontaneous proliferation and IL-2 production. Therefore, B cells from MRL/Mp-lpr/lpr mice appear to possess unique features that enable them to activate autoreactive T cells more effectively than B cells from other mice bearing the lpr/lpr gene.

Animals↗

PubMed1988

The role of antigen-presenting B cells in T cell priming in vivo. Studies of B cell-deficient mice.

Mice rendered B cell deficient by treatment with rabbit anti-mouse IgM (anti-mu) antibodies from birth fail to respond when primed with soluble protein antigens in CFA, as measured by T cell proliferation when challenged with antigen in vitro. The role of B cells in T cell priming in vivo was examined by adoptively transferring hapten-specific B cells into anti-mu mice, followed by immunization with haptenated Ag in CFA. The T cell proliferative response to OVA of anti-mu BALB/c mice was partially restored by the administration of TNP or FITC-specific B cells and immunization with TNP-OVA or FITC-OVA, respectively. This reconstitution was Ag-specific, inasmuch as hapten-binding B cells restored the T cell responses to OVA in mice immunized with the same hapten coupled to OVA. The mechanism of B cell reconstitution of T cell priming in anti-mu mice was addressed using parental to F1 B cell transfers. The Ia restriction pattern of the activated T cells from these mice indicated that both direct presentation of Ag by transferred B cells and antibody-mediated enhancement of Ag presentation by non-B, host Ag-presenting cells occurred. Thus, Ag-specific B lymphocytes play a critical role in priming of T cells in vivo.

Animals↗

PubMed1988

Abnormal T cells from MRL/Mp-lpr/lpr mice do not respond to anti-T-cell-receptor antibody or tumor promoter and calcium ionophore A23187 despite the presence of the T-cell-receptor complex and protein kinase c.

Abnormal T cells from autoimmune MRL/Mp-lpr/lpr mice express T-cell-receptor complexes on their surfaces. These receptors are nonfunctional, since monoclonal anti-T-cell-receptor antibody-conjugated beads, which normally activate receptor-bearing T cells, were unable to activate these abnormal T cells. In addition, these abnormal T cells are unresponsive to the synergistic effect of phorbolmyristate acetate (PMA) and calcium ionophore A23187, as quantitated by proliferation, interleukin-2(IL-2) production, and the expression of IL-2 receptors. The failure of abnormal T cells to respond to PMA is not due to the absence of PMA receptors since Scatchard plot analysis reveals that there are 1-1.5 X 10(5) PMA-binding sites/cell with a Kd of 6-10 nM on these abnormal T cells. Similar to normal T lymphocytes, protein kinase c activity can be readily detected in the cytosolic fraction of these abnormal T cells. More importantly, in vitro culture of the abnormal T cells with PMA results in translocation of protein kinase c activity from the cytosolic fraction to the membrane fraction. From these experiments we concluded that the defect in the signal-transducing machinery in MRL/Mp-lpr/lpr T cells is not due to the lack of PMA receptors or the absence of protein kinase c activity, but may result from events which occur after the activation and translocation of protein kinase c. However, whether defects in response to a physiological stimulus (i.e., anti-receptor antibody) could occur in a step prior to protein kinase c activation remains to be determined.

Animals↗

PubMed1988

Effects of in vivo monoclonal anti-I-A antibody treatment in neonatal mice on intrathymic and peripheral class II antigen expression.

Intrathymic, Ia-bearing antigen-presenting cells (APC) are believed to play an important role in the development of a mature, functional T-cell repertoire. We used chronic in vivo treatment of neonatal mice with anti-I-A monoclonal Ab (MAb) to examine the expression of I-A and I-E antigens on intrathymic and peripheral APC. Three weeks after continuous treatment with anti-I-A MAb, FACS analysis of unfractionated spleen cells revealed a 75-90% reduction in the number of I-A bearing cells. Splenic antigen-presenting capacity measured by the ability of unseparated or density gradient-enriched APC to stimulate I-A- or I-E-reactive T-cell hybridomas was also greatly reduced. In contrast to the expression of I-A and I-E molecules in the splenic APC, anti-I-A MAb treatment resulted in decreased thymic APC I-A expression without significant changes in I-E as measured by FACS analysis. This was confirmed in functional studies in which allo-I-A- or auto-I-A-reactive T-cell hybridomas could not be stimulated by treated thymic APC. Unlike splenic APC, anti-I-A-treated thymic APC did not differ significantly from normals in their ability to stimulate allo-I-E-reactive T hybridomas. This lack of linkage or comodulation of I-A and I-E expression on thymic but not splenic APC may allow us to study the role of I-A molecules and I-E molecules on the development and expansion of functional, mature T-cell repertoires.

Animals↗