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A Kelso

Publications and source records attributed to A Kelso.

At least 91 records · Page 5Linked to original sources
PubMed1985

Characteristics of colony-stimulating factor production by murine T-lymphocyte clones.

From a panel of cloned interleukin-2-dependent murine T-lymphocyte lines, several clones were identified that secreted high titers of one or more of the colony-stimulating factors (CSFs): granulocyte-macrophage CSF, multi-CSF (or interleukin 3), and human eosinophil CSF. These clones were used to examine the parameters of CSF production, including stimuli required, kinetics, serum concentration, and the cell dose and proliferative state of the clone. Maximal production of CSFs and interleukin 2 was stimulated by the lectin concanavalin A, which induced a burst of secretion over a 12- to 20-h period, during which all factors were released at similar rates. CSF production was not stimulated by interleukin 2 and occurred independently of clonal proliferation.

Animals↗
PubMed1984

Comparison of thymic and peripheral T cell Ly-2/3 antigens.

Major structural differences occur between the thymic and peripheral T cell forms of the Ly-2/3 antigen. Thymus Ly-2/3 consists of similar amounts of two types of disulfide-linked heterodimer, alpha beta and alpha' beta (Mr alpha = 38000, Mr alpha' = 35000, Mr beta = 30000). In contrast material from peripheral T cells consists almost exclusively of alpha beta dimers. The alpha chains of thymus and peripheral T cells differ also in isoelectric point with the thymic alpha chain being the more acidic. Based on peptide mapping experiments the alpha and alpha' chains of thymus are likely to be alternatively modified forms of the same polypeptide backbone. Individual T cell clones or T cell tumors propagated in vitro exhibit either a typical thymus or a typical peripheral T cell Ly-2/3 polypeptide pattern indicating that the synthesis of both alpha and alpha' chains can occur in the same cell. The heterogeneity of thymic Ly-2/3 can be considerably reduced by removal of sialic acid residues, and after desialylation the alpha chains of thymus and a cloned cytotoxic T lymphocyte (CTL) line cannot be electrophoretically distinguished. If Ly-2 structures affected the antigen specificity of CTL, a different structural variant would be expected in individual clones. The electrophoretic identity of desialylated thymus and CTL alpha chains suggests that Ly-2 does not exhibit clonal variation in polypeptide structure and, therefore, cannot contribute to antigen specificity.

Animals↗
PubMed1984

Intracellular destruction of Leishmania tropica by macrophages activated with macrophage activating factor/interferon.

Supernatants (SN) from cloned T cell lines, lymphokine secreting tumour cell lines and mixed lymphocyte culture were analysed for their ability to induce murine peritoneal exudate cell (PEC) macrophages (M phi) parasitized with Leishmania tropica to destroy the parasite. The ability of the SN to induce parasite destruction in parasitized PEC M phi correlated with their content of macrophage activating factor/interferon. Neither granulocyte-macrophage colony stimulating factor, M phi colony stimulating factor nor interleukin 2 was required for the induction of parasiticidal activity by infected PEC M phi. Similar results were also obtained using either a different Leishmania species, Leishmania enriettii, or a second source of cells: bone marrow derived macrophages.

Animals↗
PubMed1984

Secretion of interleukin 2, macrophage-activating factor, interferon, and colony-stimulating factor by alloreactive T lymphocyte clones.

Sixty-four murine alloreactive, cytolytic and noncytolytic , T lymphocyte clones were tested for the production of interleukin 2 (IL 2), macrophage-activating factor (MAF), interferon (IFN), and colony-stimulating factor (CSF). Approximately 90% of both cytolytic and noncytolytic clones secreted MAF and IFN upon antigen or mitogen stimulation. IL 2, in contrast, was only released in detectable amounts by 50% of noncytolytic clones and 50% of a subclass of cytolytic clones in which the proliferation was independent of exogenous IL 2 ("antigen-driven" clones); IL 2-dependent cytolytic clones did not release measurable IL 2. CSF was secreted by approximately 90% of noncytolytic and IL 2-independent cytolytic clones and 40% of IL 2-dependent cytolytic clones. The analysis reported here revealed a strong quantitative correlation between the titers of MAF and IFN released by the clones, suggesting that these two assays may measure the same lymphokine. Although the other activities measured were not directly correlated, a broad association was noted between IL 2 secretion and the production of high titers of MAF, IFN, and CSF. Thus, noncytolytic and IL 2-independent cytolytic clones on average released significantly higher titers of these factors than IL 2-dependent cytolytic clones.

Animals↗
PubMed1984

Glucocorticoid inhibition of lymphokine secretion by alloreactive T lymphocyte clones.

The effect of glucocorticoids on lymphokine production by T lymphocytes was examined by using long-term alloreactive T cell clones that secreted one or more of the lymphokines interleukin 2 (IL 2), interferon-gamma, macrophage-activating factor (MAF), and colony-stimulating factor when stimulated by an antigen or a mitogen. Production of all of these four lymphokines was inhibited when glucocorticoids were added at physiologic concentrations (10(-8) to 10(-6) M) to clones stimulated with concanavalin A (Con A). Clones were heterogeneous with respect to their sensitivity to glucocorticoid inhibition of MAF production; cytolytic clones were generally more resistant than noncytolytic clones. The glucocorticoid dexamethasone (Dex) and an IL 2-containing supernatant exerted opposing effects on clonal MAF production. Kinetics experiments showed that Dex inhibited MAF production by reducing the rate of secretion without causing a compensatory increase in the duration of secretion, whereas the IL 2 source increased the rate and the total amount of MAF secretion. Dex abrogated the effect of IL 2. Inhibition by Dex was apparent from the earliest time of detectable MAF production (about 4 hr after stimulation) and increased with longer exposure until production ceased (12 to 24 hr). Pre-exposure and removal of Dex before Con A stimulation also inhibited MAF release. Effects of Dex on lymphokine secretion by clones could be dissociated from effects on their growth in response to stimulator cells and IL 2. Factor production by the 16 clones tested was inhibited to some degree. Proliferation, however, by two of these clones (both cytolytic) was unaffected by Dex, whereas proliferation of two noncytolytic clones was strongly inhibited even in the presence of a saturating dose of IL 2.

Animals↗
PubMed1984

Interleukin 2 enhancement of lymphokine secretion by T lymphocytes: analysis of established clones and primary limiting dilution microcultures.

The effect of exogenous interleukin 2 (IL 2) on lymphokine production by T lymphocytes was examined in two systems: the secretion of macrophage-activating factor (MAF) and interferon (IFN) by cloned long-term T cell lines, and a limiting dilution system for estimating the frequency of precursors of MAF-secreting cells in normal spleen. An IL 2-containing, MAF- and IFN-free supernatant from the EL-4 thymoma (EL-4 SN) significantly enhanced release of MAF and IFN by mitogen- or antigen-stimulated, cytolytic or noncytolytic T lymphocyte clones directed against alloantigens or Moloney leukemia virus-associated antigens. Highly purified IL 2 produced equivalent enhancement as EL-4 SN in cultures of alloreactive clones stimulated with concanavalin A. Kinetics experiments showed that EL-4 SN increased both the rate and duration of MAF release by T cell clones. EL-4 SN also increased MAF production when added during restimulation of limiting dilution cultures of positively selected Lyt-2+ and Lyt-2- C57BL/6 splenic T lymphocytes activated against DBA/2 alloantigens. This enhancement resulted in a threefold increase in the apparent precursor frequency of MAF-secreting cells among Lyt-2+ lymphocytes, but did not affect the frequency among Lyt-2- cells. Additional analysis indicated that average MAF production in cultures of Lyt-2-+ cells was sixfold lower than in cultures of Lyt-2- cells, and hence that EL-4 SN allowed detection of a significant proportion of Lyt-2+ cell cultures secreting low levels of MAF. Under these improved conditions, the MAF assay detected the majority of responding Lyt-2+ and Lyt-2- lymphocytes.

Animals↗
PubMed1983

Cytolytic T lymphocyte clones that proliferate autonomously to specific alloantigenic stimulation. II. Relationship of the Lyt-2 molecular complex to cytolytic activity, proliferation, and lymphokine secretion.

Previous analyses of the inhibitory effects of anti-Lyt-2 monoclonal antibodies (mAb) on cytolytic activity suggested that Lyt-2/3 antigens expressed on the surface of murine cytolytic T lymphocytes (CTL) are involved in antigen recognition. In the present study, we investigated the effects of anti-Lyt-2 mAb (in the absence of complement) on the functional activities of H-2K/D-specific Lyt-2+ CTL clones that proliferate to antigenic stimulation in the absence of helper T cells or added interleukin 2 (IL 2) and secrete lymphokines. For those clones that were inhibited in cytolysis by anti-Lyt-2 mAb, a parallel inhibition of antigen-dependent proliferation and lymphokine secretion (interferon, macrophage-activating factor) was observed. Inhibition of proliferation or lymphokine secretion could be overcome by the addition of IL 2 or lectin, respectively. Collectively, these results would strongly suggest that anti-Lyt-2 mAb were inhibiting CTL antigen recognition. Not all CTL clones, however, were inhibited in cytolysis by anti-Lyt-2 mAb, in which case proliferation and lymphokine secretion were similarly unaffected. This heterogeneity of Lyt-2+ CTL clones in their susceptibility to inhibition of cytolytic activity, proliferation, and lymphokine secretion by anti-Lyt-2 mAb is discussed in the context of a model proposing that Lyt-2/3 molecules function to stabilize the interaction between CTL receptors and the corresponding target/stimulating cell antigens. Such a stabilization may be required by CTL possessing few and/or low affinity receptors.

Animals↗
PubMed1983

Stimulator cell requirements for allospecific T cell subsets: specialized accessory cells are required to activate helper but not cytolytic T lymphocyte precursors.

Murine cortisone-resistant thymocytes were separated by staining with monoclonal anti-Lyt-2 antibody and FMF into Lyt-2- and Lyt-2+ subsets in order to analyze the nature of stimulator accessory cells required to activate each of these functionally distinct T cell subpopulations. The Lyt-2- fraction was able to proliferate but not to generate cytotoxic cells when stimulated by irradiated allogeneic spleen cells. Fractionation of the stimulator population showed that low numbers of dendritic cells and splenic macrophages, but not equivalent numbers of whole spleen cells or peritoneal macrophages, were able to stimulate the Lyt-2- population. On the other hand, the Lyt-2+ population, which showed little if any proliferation in response to irradiated spleen cells, contained all the precursors of cytolytic T lymphocytes. In contrast to the highly specific stimulator requirement of the Lyt-2- fraction, allospecific cytotoxic cells were generated from Lyt-2+ cells by any alloantigen-bearing stimulator cell provided interleukin 2 was present. This was confirmed by limiting dilution analysis: alloreactive CTL-P frequencies in spleen and thymus were not influenced by the nature of the stimulator cell. These data collectively indicate that heterogeneous Ia+ accessory cells are required to stimulate helper but not cytolytic T cell precursors.

Animals↗
PubMed1982

Precursor frequency analysis of lymphokine-secreting alloreactive T lymphocytes. Dissociation of subsets producing interleukin 2, macrophage-activating factor, and granulocyte-macrophage colony-stimulating factor on the basis of Lyt-2 phenotype.

The frequencies of precursors of C57BL/6 T lymphocytes that respond to DBA/2 alloantigens by secreting the lymphokines interleukin 2 (IL-2), macrophage-activating factor (MAF), and granulocyte-macrophage colony-stimulating factor (GM-CSF) have been directly compared with cytolytic T lymphocyte precursor (CTL-P) frequencies in limiting dilution microcultures established from spleen cells positively or negatively selected on the basis of Lyt-2 phenotype. A clear dichotomy was observed between CTL-P, which were contained in the Lyt-2+ fraction, and precursors of IL-2-secreting cells, which were detected almost exclusively in the Lyt-2- population. In contrast, precursors of cells secreting MAF and GM-CSF were found in both populations: almost all responding cells from the Lyt-2- fraction produced both these factors, whereas the precursor frequency of MAF-secreting and GM-CSF-secreting cells was three- to fourfold lower in the Lyt-2+ population. These frequency data were consistent with quantitative differences observed in the average production of these lymphokines by Lyt-2+ and Lyt-2- populations.

Animals↗
PubMed1982

Production of macrophage-activating factor by T lymphocyte clones and correlation with other lymphokine activities.

The production of macrophage-activating factor (MAF) by antigen-stimulated murine T lymphocyte clones has been compared with their cytolytic function and release of other lymphokines. MAF activity was measured by the capacity of peptone-induced peritoneal exudate cells or bone marrow-derived macrophages to lyse 51Cr-labeled tumor cells after incubation with supernatant from the stimulated T cells and a nonactivating, amplifying dose of lipopolysaccharide. Of 72 clones generated against H-2, MIs, H-Y, or Moloney leukemia virus-associated antigens, 68 were found to produce detectable quantities of MAF. Release of MAF by clones 1) occurred within 1 to 12 hr of exposure to antigen, 2) required stimulation with cells of the relevant antigenic specificity, and 3) could also be induced by concanavalin A, indicating that the cloned cells were the source of the activity. The capacity of a clone to produce MAF was independent of its antigenic specificity, cytolytic activity, or ability to produce interleukin 2 or granulocyte-macrophage colony-stimulating activity. In contrast, production of interferon and MAF was not dissociated for any of the clones tested.

Animals↗
PubMed1981

Absorption of normal lymphocytes on allogeneic spleen monolayers: depletion of alloreactivity is due to inhibition of CTL induction by released monolayer cells.

A technique for the haplotype-specific depletion of precursors of alloreactive cytolytic T lymphocytes (CTL-P) by absorption of unprimed spleen cells on allogeneic lymphocyte monolayers has been examined. When H-2d spleen cells were incubated on monolayers of H-2b spleen cells and the nonadherent cells were cultured in mixed leukocyte culture (MLC), CTL activity generated against the monolayer haplotype was 30- to 1000-fold lower than the equivalent cultures of unabsorbed H-2d cells. Cytolytic reactvity to a 3rd-party haplotype, H-2k, was reduced no more than 6-fold. However, culture of the same cells at limiting dilution indicated that the frequency of CTL-P against the monolayer haplotype in monolayer-nonadherent H-2d populations was not significantly different from the frequency in normal H-2d spleen. It was noted that MLC of monolayer-nonadherent H-2d populations were highly cytolytic for H-2d target cells. This reaction was reduced and the ability to generate anti-H-2b CTL was restored when the nonadherent cells were treated with anti-H-2b antibody and complement to eliminate contaminating monolayer cells released during absorption, and when monolayers were prepared from spleen cells depleted of Lyt 2-bearing cells (and hence CTL-P). These data suggested that the reduction in anti-H-2b reactivity of monolayer-nonadherent cells in MLC was due to inhibition by the competing anti-H-2d reaction of contaminating, monolayer-derived CTL-P. Although fluorescent labeling of monolayer cells indicated that these cells represented only 10% of the nonadherent population, flow cytometry and further limiting dilution analysis demonstrated that cells that detached from H-2b monolayers during absorption were enriched 2-fold in T lymphocytes and CTL-P over normal spleen. The strength of the anti-H-2d reaction by a minority of monolayer cells can thus be attributed both to the higher frequency of H-2b anti-H-2d than H-2d anti-H-2b CTL-P in spleen populations and to the preferential detachment of monolayer T lymphocytes during absorption.

Absorption↗
PubMed1979

The antigen-specific signal in T-lymphocyte activation by alloantigen.

Current concepts of the mechanism of alloactivation of cytotoxic lymphocytes and the identity of the target cell determinants with which they interact are reviewed. The results of a quantitative analysis of the stimulatory activity of different forms of antigen and the role of a costimulator factor are presented. These lead to the conclusions that SD antigens are not the target cell antigens and that existing theories of cytotoxic T cell activation are inadequate. A new theory of activation of alloareactive cytotoxic lymphocytes is proposed.

Animals↗