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F W Fitch

Publications and source records attributed to F W Fitch.

At least 127 records · Page 7Linked to original sources
PubMed1982

Alloreactive cloned T cell lines. VI. Multiple lymphokine activities secreted by helper and cytolytic cloned T lymphocytes.

Culture supernatants generated by alloantigenic or lectin stimulation of a cloned helper T lymphocyte, designated L2, contain interleukin 2 (IL 2), granulocyte/macrophage colony-stimulating factor (CSF), B cell stimulating factor (BCSF), macrophage (Ia+)-recruiting factor (MIRF), (Ia+)-inducing activity, gamma-interferon, Fc receptor-enhancing activity, macrophage migration inhibitory factor (MIF), macrophage activation factor (MAF), interleukin 3 (IL 3), and a factor responsible for prolonging the synthesis and secretion of the fourth and second components of complement by guinea pig peritoneal macrophages. Erythropoietin was not detected. A spontaneously arising variant of L2, designated L2V, produces much lower quantities of macrophage-stimulating activities, IL 2, and interferon. However, when compared to L2, L2V produces much higher levels of BCSF, equivalent amounts of IL 3, and slightly smaller amounts of CSF. Unlike L2V, a cytolytic clone, designated L3, secretes lymphokines that primarily affect macrophage function. The time course of lymphokine production by L2 cells indicates that for the six lymphokine activities studied there are three different times at which maximal or near maximal levels are reached, as follows: 1) IL 2, 12 to 24 hr; 2) IL 3 and CSF, 24 to 48 hr; and 3) (Ia+)-inducing activity, MAF, and interferon, 48 hr or later. Only IL 2 activity disappears during the 8-day culture cycle. The time course data and the differential production of activities by the three types of lymphocyte clones suggest that at least four terminal effector lymphokine molecules account for the ten biologic activities tested.

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PubMed1982

High molecular weight lymphocyte surface proteins are structurally related and are expressed on different cell populations at different times during lymphocyte maturation and differentiation.

HMW lymphocyte surface proteins T20 and B220, which are expressed on T and B cells, respectively, have been found to be extensively related in structure, beyond what would be expected by the sharing of the determinant detected by monoclonal antibody 13/2. In addition, another HMW protein (T200A) has been discovered, which is preferentially expression proliferating T cells, and which exhibits significant structural homology with T200, but does not express the 13/2 determinant. T200A bears a novel antigenic determinant, detected by monoclonal antibody BS-S28E, which is not shared by either T200 or B220. A fourth HMW protein (170/100) has been found, which is expressed on most lymphocytes, but which is neither structurally nor antigenically related to T200A, T200, or B220. Monoclonal antibodies reactive with 170/100 inhibit T cell-mediated cytolysis, although monoclonal antibodies reactive with T200A, T200, or B220 do not.

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PubMed1982

I-A antigens on cloned alloreactive murine T lymphocytes are acquired passively.

Cloned lines of alloreactive cytolytic and amplifier T lymphocytes have been examined for expression of I-A antigens. Using flow cytofluorometry and monoclonal antibodies, MHC antigens representing both I-A and H-2K or D determinants were reproducibly detected on the cell surface of these cloned T lymphocytes. All cloned lines examined expressed H-2K or D antigens representing the MHC haplotype appropriate to their strain of origin. However, I-A as well as H-2K or D antigens appeared to be acquired passively from the stimulating cell population. Within the lower limits of detection using the fluorescence-activated cell sorter, evidence suggesting endogenous synthesis of I-A antigens by these cloned T lymphocytes could not be demonstrated. Further, the observed binding appeared to be nonspecific, because material originating from allogeneic, syngeneic, or third-party stimulating cells could be observed under appropriate conditions.

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PubMed1981

Lyt-2-/Lyt 3- variants of a cloned cytolytic T cell line lack an antigen receptor functional in cytolysis.

To investigate the role of Lyt-2 and Thy-1 in cytolysis, we have generated, by ethyl methanesulfonate mutagenesis and selection, variants of the cloned cytolytic T lymphocyte line L3 that specifically lack either Lyt-2 or Thy-1. An analysis of these variants indicates that neither Lyt-2 nor Lyt-3 is responsible for the lethal hit, but suggests that Lyt-2 and/or Lyt-3 are required for an antigen receptor functional in cytolysis. The data also suggest that the expression of Lyt-3 on the cell surface is not independent of the expression of Lyt-2. Finally the data indicate the Thy-1 plays no role in cytolysis.

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PubMed1981

Enumeration of alloreactive helper T lymphocytes which cooperate with cytolytic T lymphocytes.

The number of alloreactive helper T lymphocytes (HTL) which cooperate with cytolytic T lymphocytes have been quantified in a sensitive limit dilution system. Approximately 1 in 330 splenic T lymphocytes developed helper activity in response to alloantigen of a single haplotype. Most HTL appeared to cooperate nonspecifically with the cytolytic cells. A significant number of alloreactive HTL precursors recognized H-2 K or D alloantigen, but roughly 6-fold more HTL precursors responded to H-2 I, and roughly 20-fold more responded to non-H-2, presumably Mls, alloantigen. These results support the hypothesis that alloantigen encoded by the H-2 I and non-H-2 Mls regions preferentially stimulate helper T lymphocytes, while alloantigens encoded by the H-2 K and D regions preferentially stimulate cytolytic T lymphocytes.

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PubMed1981

Structural differences in cell surface T25 polypeptides from thymocytes and cloned T cells.

The molecule bearing the Thy-1.2 antigen, T25, has been isolated from fractionated thymocytes as well as from cloned cytolytic and helper T cells by immune precipitation with monoclonal antibodies. Using NaDodSO4/polyacrylamide gels cross-linked with N,N'-diallytartardiamide, electrophoretic analyses of the precipitates revealed a heterogeneous pattern of polypeptide bands, ranging in apparent molecular weight from 28,000-36,000 daltons. Thymocytes separated on the basis of Thy-1.2 surface antigen density were found to differ not only in amount of Thy-1.2 expressed, but also in the structure of the surface T25 molecules isolated from each subpopulation. This structural variation was evidenced in changes detected in the relative density and electrophoretic mobility of T25 band patterns obtained on SDS gels. Differences in T25 band patterns were also observed in polypeptides isolated from cloned cytolytic or helper T cells. These data suggest that although surface T25 is structurally heterogeneous, the pattern of heterogeneity can differ from cell to cell, or from population to population. Changes in T25 structure appear to correlated with differences in either T lymphocyte maturation or T cell function.

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PubMed1981

T lymphocyte clones having defined immunological functions.

T cell clones are proving to be useful for analysis of various immunological phenomena. Although some clones grow well in IL 2-containing CM alone, the combination of antigen, "filler" cells, and CM improves cloning efficiency and may favor the retention of stable clones expressing a "normal" phenotype. The antigen recognition repertoire of T cells appears to be much larger than was predicted using conventional approaches. CTLs can react with at least 23 different determinants on the H-2Kb molecule of the MHC. CTLs demonstrate MHC-restricted recognition of viral and haptenic determinants, but the restriction is not strict for all cloned cells, and a variety of reactivity patterns are found. Antigen-responsive cloned T cells appear to recognize antigens in association with alloantigens encoded by the I-A region of the MHC. However, the relevant structures formed in hybrid animals include all possible combinations of peptides including those formed by trans-complementation of I-A and I-E region gene products. Culture supernatants from antigen-responsive cloned T cells contain a variety of biological activities including IL 2, B cell-stimulating factor, colony-stimulating factor, migration inhibition factor, interferon, and factors that modulate expression of Ia antigens on macrophages and influence production of complement components. These factors may be important in mediating interactions between T lymphocytes and other cells. Cloned T cells have proved to be useful for studying the importance of particular phenotypic characteristics associated with given immunological functions. Although expression of Lyt-2 generally correlates with cytolytic activity and Lyt-1 with helper activity, important exceptions have been found with T cell clones. Cloned T cells promise to be useful for further characterization of the molecular basis of immune responses.

Animals↗
PubMed1981

Alloreactive cloned T cell lines. II. Polyclonal stimulation of B cells by a cloned helper T cell line.

A cloned helper T cell line, L2, has been derived that promotes the proliferation of cytolytic T cells with the concomitant expression of cytolytic activity. L2 helper cells also cause a polyclonal stimulation of B cells in the absence of antigen, as measured by the number of total plaque-forming cells (PFC) as well as those generated toward TNP or SRBC. The L2 helper cell function is dependent on cell number, is radioresistant, and is mediated via soluble factor(s). Maximum levels of PFC were generally observed after 4 days of culture, with IgM-secreting B cells being predominantly induced in these cultures. Both the proliferation of and stimulation by L2 helper cells are activated by Misa determinants. F1 progeny from a mating of CBA/N and DBA/2 (Mlsa) that did not bear Mlsa (NDF1) were nonstimulatory, whereas those F1 animals bearing Mlsa (DNF1) induced L2 helper-cell proliferation and function. L2 helper-cell recognition of Mlsa determinants present on the responding B cell surface was not required for polyclonal helper-dependent stimulation in vitro. L2 cells stimulated polyclonal antibody secretion in syngeneic as well as allogeneic B cells. Since Mls antigens are not expressed on T cells, these results indicate that regulatory T cell circuits are initiated by non-T cells, possibly B cells.

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PubMed1981

Alloreactive cloned T cell lines. III. Accessory cell requirements for the growth of cloned cytolytic T lymphocytes.

We examined the role of accessory cells that cooperated with the cloned cytolytic T cell line, L3. Accessory cells and T cell growth factors (TCGF) acted synergistically to stimulate cloned L3 CTL to grow and produce cytolytic activity. Accessory cells were non-T, radioresistant, plastic adherent M phi-like cells that interacted with cloned L3 CTL via soluble factors. Peritoneal M phi, at low density, also cooperated with L3 cells but at high density, inhibited L3 cells. Both accessory and inhibitory M phi acted upon L3 CTL without the intervention of other T lymphocytes or nonadherent cells. Other published reports indicate that M phi may promote cytolytic activity indirectly, amplifying TCGF production by helper T lymphocytes. This report indicates that M phi may also promote cytolytic activity directly, amplifying the response of CTL to TCGF.

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PubMed1981

Alloreactive cloned T cell lines. V. Differential kinetics of IL 2, CSF, and BCSF release by a cloned T amplifier cell and its variant.

A noncytolytic, Thy-1+, MIs-responsive cloned T amplifier cell, designated L2, derived from secondary C57BL/6 anti-DBA/2 mixed leukocyte culture was found to produce IL 2 (Interleukin 2), granulocyte/macrophage colony-stimulating factor (CSF), and a polyclonal B cell-stimulating factor (BCSF) after alloantigenic stimulation. IL 2 activity was present transiently, with maximal levels observed 12 to 24 hr after exposure to alloantigen. Only trace amounts were present 96 hr after initiation of culture. CSF and BCSF activities were present at high levels by 24 hr and remained elevated throughout an 8-day culture period. Further evidence that the lymphokine(s) having IL 2 activity is different from those having CSF and BCSF activities was provided by L2V, a variant of L2 that did not produce IL 2. The time course of CSF and BCSF production by L2V after stimulation with alloantigen was similar to that found with L2, although IL 2 activity was not detected at any time. Since the release of lymphokines from both L2 and L2V cells could be induced by Con A in the absence of stimulating alloantigen, it is likely that the biologically active factors were produced by the cloned T cell.

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