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Biomedical subjects

A Kelso

Publications and source records attributed to A Kelso.

At least 55 records · Page 3Linked to original sources
PubMed1993

Lymphokine synthesis in vivo in an acute murine graft-versus-host reaction: mRNA and protein measurements in vivo and in vitro reveal marked differences between actual and potential lymphokine production levels.

The in vivo activation of lymphokine-producing cells was analyzed in the first 7 days of an acute graft-versus-host reaction (GVHR) induced by injection of C57BL/6 spleen cells into irradiated DBA/2 mice. Although the GVHR was accompanied by a 1000-fold increase in serum IL-6 titers, circulating levels of other lymphokines were low (IL-3, IFN-gamma, and GM-CSF) or undetectable (IL-2 and IL-4). Spleen and lymph node cells from these mice nevertheless produced elevated levels of IL-3, IFN-gamma, GM-CSF, and IL-6 when cultured for 24 h without stimulation; culture with anti-CD3 antibody further increased IL-2, IL-3, IL-4, IFN-gamma, and GM-CSF production by at least 20-fold. Both constitutive and anti-CD3-induced synthesis of all the lymphokines was mediated by CD3+ cells. Messenger RNA analyses revealed the presence of IL-6, IFN-gamma, and GM-CSF transcripts in freshly harvested GVHR spleen cells and increased expression of IL-2, IL-3, IL-4, IFN-gamma, and GM-CSF mRNAs following anti-CD3 stimulation in vitro. In vivo, however, IL-3 mRNA was barely detectable even following cDNA amplification by polymerase chain reaction. In vivo restimulation of day 5 GVHR mice by injection of concanavalin A enhanced expression of IL-3, IL-6, IFN-gamma, and GM-CSF mRNAs and markedly increased serum titers of the corresponding lymphokines, which peaked 6-12 h after injection at levels at least 10- to 100-fold higher than in concanavalin A-treated normal mice.2+ for high-level synthesis of all these lymphokines.

Animals↗
PubMed1993

Resistance of BALB/c mice to Leishmania major infection is associated with a decrease in the precursor frequency of antigen-specific CD4+ cells secreting interleukin-4.

BALB/c mice are highly susceptible to infection with the protozoan parasite Leishmania major and develop a chronic fatal disease. They can, however, be manipulated to resist disease and this has been shown to correlate with increased expression of IFN-gamma mRNA and the absence of IL-4 mRNA in the draining lymph nodes and spleens of these animals. Here we show that anti-IL-4 or anti-CD4 treatment of BALB/c mice resulted in a reduction in the size of the lesion and in the number of parasites in the draining lymph nodes compared with untreated mice. The precursor frequency of CD4+ T cells proliferating in response to Leishmania antigens in vitro in the treated animals was not significantly different from untreated animals. Analysis of the lymphokines secreted by the clonal progeny of these cells showed that the precursor frequency of IL-4 secreting clones was at least 10-fold lower in animals treated with either mAb. However, there was no reciprocal increase in the precursor frequencies of IFN-gamma secreting clones. Comparisons of the total number of precursors of specific CD4+ cells secreting IFN-gamma showed that anti-CD4-treated animals, which are resistant to disease, had considerably fewer for the first 6 weeks than untreated mice with chronic disease. Protection of BALB/c mice was therefore associated with a reduction in the numbers of precursors of cells secreting IL-4 without a concomitant increase in the number of precursors of IFN-gamma secreting cells.

Animals↗
PubMed1993

Interleukin-4 but not gamma interferon production correlates with the severity of murine cutaneous leishmaniasis.

For murine cutaneous leishmaniasis, data to date suggest a correlation between the presence of gamma interferon (IFN-gamma) and resistance in C57BL/6 mice and the presence of interleukin-4 (IL-4) and disease in BALB/c mice. In this study, 13 inbred strains of mice covering the range of susceptibility to disease were infected with Leishmania major to determine whether the subsequent expression of IFN-gamma or IL-4 is a reliable indicator of cure or progressive disease. The presence of IL-4 and IFN-gamma mRNAs in the draining lymph nodes was examined 9 weeks after infection, when differences in disease severity became obvious. There were large differences in the levels of IL-4 mRNA among the different strains, whereas IFN-gamma mRNA was detected at similar levels in all strains. The levels of IL-4 mRNA correlated with lesion score, with susceptible and intermediate strains containing up to 100-fold more than any of the resistant strains. Differences in the levels of IFN-gamma mRNA were within only a fourfold range, with significant overlap among susceptible, intermediate, and resistant strains. Similarly, the levels of IFN-gamma secreted in vitro by lymph node cells from infected mice in response to L. major antigens were within a 10-fold range for most strains, and there was no correlation with lesion score. Analysis of Leishmania-specific antibody levels revealed a correlation between immunoglobulin G1 (IgG1) titers and lesion score, consistent with the role of IL-4 as a switch factor for IgG1. In contrast, there was no correlation between IgG2a titers and lesion score, supporting the notion that IFN-gamma synthesis (which promotes IgG2a production) is not correlated with disease state. These data suggest that along the spectrum of murine cutaneous leishmaniasis, IL-4 is a reliable indicator of disease, but IFN-gamma is not prognostic for resistance.

Animals↗
PubMed1993

Cytokine production in the murine response to brucella infection or immunization with antigenic extracts.

In order to induce acquired cellular resistance (ACR) to facultative intracellular bacterial pathogens, infection with live organisms is required. It is possible that different cytokine responses to live bacteria or their extracted antigens could account for their different abilities to induce ACR. Therefore, mice were infected with live attenuated Brucella abortus vaccine strain 19, and their ability to produce cytokines, both in vivo and in vitro, was investigated over 12 weeks of infection. This was compared with the response to injection of soluble brucella proteins (SBP). During infection, serum levels of interleukin-6 (IL-6) were markedly increased over a period of 4 weeks during the peak of infection. SBP plus adjuvant induced a transient increase in serum IL-6. IL-1 and tumour necrosis factor-alpha (TNF-alpha) remained undetectable in both instances. Spleen cells taken at intervals after infection and cultured with brucella antigens produced high titres of IL-6, IL-1 and TNF-alpha. Immunization with SBP was less efficient than live infection at inducing these cytokines. Of the characteristically T-cell-derived lymphokines, interferon-gamma (IFN-gamma) production rose 2 weeks after infection, peaking at 6 weeks, while IL-2 was not detected until 6 weeks post-infection. Granulocyte-macrophage colony-stimulating factor (GM-CSF) was produced in substantial amounts, but IL-3 production was minimal. In contrast, spleen cells from mice immunized with SBP produced IL-2 but failed to produce IFN-gamma. The implications of these results for the induction of ACR are discussed.

Animals↗
PubMed1993

Contact sensitization to oxazolone: involvement of both interferon-gamma and interleukin-4 in oxazolone-specific Ig and T-cell responses.

The synthesis and role of several lymphokines were examined during contact sensitization to oxazolone (OX). Application of OX to the skin of mice increased the delayed-type hypersensitivity (DTH) response to challenge, serum titres of OX-specific IgG1 and IgG2a, and draining lymph node cell (LNC) numbers. At day 3, LN contained detectable interleukin-4 (IL-4), interferon-gamma (IFN-gamma) and granulocyte-macrophage colony-stimulating factor (GM-CSF) but not IL-2 or IL-3 mRNAs; IL-3 and higher levels of IL-4, IFN-gamma and GM-CSF mRNAs were measured after 24 hr culture with anti-CD3 antibody in OX-primed but not unprimed LNC. As a result of sensitization, LNC secreted IL-3 constitutively and produced elevated levels of IL-2, IL-3, IL-4 and IFN-gamma in response to anti-CD3 antibody; a similar but weaker lymphokine response was recalled by OX-protein conjugate. CD4+ cells were the major source of the anti-CD3-induced lymphokines except IFN-gamma, which was derived mainly from CD8+ cells. Since both IL-4 and IFN-gamma were synthesized by OX-primed LNC in vivo and in vitro, their role was investigated by administering anti-lymphokine antibodies at the time of sensitization. Anti-IL-4 treatment reduced OX-specific serum IgG1 titres without affecting IgG2a titres, whereas anti-IFN-gamma treatment reduced IgG2a but not IgG1 titres. Although neither antibody altered DTH responsiveness, anti-IFN-gamma treatment markedly increased IL-4 production by CD4+ LNC and reduced IFN-gamma production in vitro, particularly by CD4+ cells. We conclude that endogenous IL-4 and IFN-gamma reciprocally influence the isotype of the Ig response to OX and that IFN-gamma also affects the relative levels of IL-4 and IFN-gamma synthesis by CD4+ LNC.

Animals↗
PubMed1992

Changes in the precursor frequencies of IL-4 and IFN-gamma secreting CD4+ cells correlate with resolution of lesions in murine cutaneous leishmaniasis.

Limiting dilution analysis was used to estimate the frequency of clonogenic Ag-specific CD4+ T lymphocytes in draining lymph nodes of mice over the course of infection with Leishmania major, and to measure the production of IL-2, IL-3, IL-4, IFN-gamma, and TNF by the resultant clones. Infection of both genetically susceptible BALB/c ("non-healer") and resistant C57BL/6 ("healer") mice resulted in at least a fourfold increase in the frequency (to about 0.3%) and at least a 10-fold increase in the total number of lymph node CD4+ cells that formed clones when cultured with L. major Ag in vitro. At 1 wk after infection, the majority of clones from BALB/c mice secreted IL-4 (precursor frequency 0.15%) and fewer secreted IFN-gamma (0.05%); this pattern remained constant for at least 8 wk after infection. In C57BL/6 mice, however, a high precursor frequency of IL-4-secreting clones was measured in the first 1 to 2 wk when the mice had lesions, but resolution of infection was associated with a decrease in the frequency of IL-4-secreting clones (from 0.13% at 2 wk to 0.03% at 4 wk) and an increase in the frequency of IFN-gamma-secreting clones (from 0.08% to 0.22%). At all stages of infection, most clones from either mouse strain secreted IL-3 and very few secreted TNF. Analysis of PCR-amplified cDNA from draining lymph nodes of infected mice also revealed that IL-4 and IFN-gamma mRNA were expressed in both mouse strains early in infection. IL-4 mRNA was the major species at 2 and 6 wk after infection in BALB/c mice, but declined relative to IFN-gamma mRNA over this time in C57BL/6 lymph nodes. Precursor frequency estimates of lymphokine-secreting CD4+ cells in draining lymph nodes therefore correlated with lymphokine expression patterns in vivo. Analysis of a panel of individual short term clones derived from mice 1 wk after infection revealed marked heterogeneity in lymphokine production patterns. In BALB/c mice, 49% secreted IL-4 without IFN-gamma, 18% secreted IFN-gamma without IL-4, and 14% secreted both IL-4 and IFN-gamma. Similarly in C57BL/6 mice, 39% secreted IL-4, 20% secreted IFN-gamma, and 17% secreted both lymphokines. Many of the clones also produced IL-3 and/or IL-2. Together the data suggest that both IL-4 and IFN-gamma are synthesized early in infection of susceptible and resistant mice as assessed by mRNA and precursor frequency analyses.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1992

Enumeration of lymphokine mRNA-containing cells in vivo in a murine graft-versus-host reaction using the PCR.

A method of enumerating lymphokine mRNA-containing cells in vivo was developed by combining limiting dilution analysis with PCR amplification of cDNA. Single-hit kinetics revealed that the PCR-limiting dilution analysis could detect a single positive cell among greater than 40,000 negative cells. With this method, spleens and lymph nodes of mice undergoing an acute allogeneic graft-versus-host reaction were found to contain lymphokine mRNA-expressing cells at frequencies of 3% for interferon gamma, 0.05% for granulocyte/macrophage colony-stimulating factor, 0.002% for interleukin 3, and 0.03% for interleukin 4; these frequencies were 20- to 175-fold higher than in lymphoid tissues of normal mice. In contrast to their low frequencies of lymphokine mRNA-containing cells in vivo, graft-versus-host reaction populations restimulated in vitro for 24 hr with anti-CD3 antibody yielded frequencies ranging from 3% for interleukin 4 to nearly 70% for interferon gamma. Furthermore, lymphokine transcripts were also detected in single micromanipulated cells from these populations. Because frequencies of anti-CD3-inducible lymphokine mRNA-containing cells in normal mice were only 0.03-1%, it was concluded that lymphoid tissues of graft-versus-host reaction mice contained high frequencies of cells that had been primed for lymphokine synthesis. Only a small fraction of these cells, however, expressed lymphokine mRNAs at a given time point in vivo.

Animals↗
PubMed1992

Murine cytolytic CD8+ T cell clones generated in a high cloning efficiency, accessory cell-free culture system express a restricted lymphokine profile.

To determine whether cytolytic T lymphocyte activity is associated with a particular lymphokine profile, lymphokine synthesis was analyzed in a large panel of primary clones derived from single murine CD8+ lymph node T cells. The clones were generated at high efficiency (60-70%), under conditions that had been optimized for the induction of specific cytolytic activity, by culture with phorbol 12-myristate 13-acetate, ionomycin, IL-2, and IFN-gamma for 6 days and then with IL-2 and IL-6 for a further 2 days. When the clones were restimulated for 24 hr with IL-2 and immobilized antibodies to CD3, CD8, and LFA-1, most secreted IL-3 and IFN-gamma and about a third secreted TNF. Although levels of production of IL-3 and IFN-gamma were positively correlated with each other (r = 0.85) and weakly correlated with cytolytic activity (r = 0.68 and 0.55, respectively). TNF titers were unrelated to any other function measured. None of the clones tested secreted detectable IL-4 or IL-6. Similarly, analysis of several clones for lymphokine mRNA expression following cDNA amplification by the polymerase chain reaction revealed the presence of IL-2, IL-3, IFN-gamma, TNF-alpha, and GM-CSF but not IL-4 or IL-6 transcripts. Cytolytic CD8+ T cell clones generated in this high efficiency, accessory cell-independent cloning system therefore expressed a restricted lymphokine profile characterized by the synthesis of IL-3 and IFN-gamma, with variable production of TNF.

Animals↗
PubMed1992

Quantitative analysis of lymphokine expression in vivo and in vitro.

Constitutive lymphokine production by cells isolated from mice injected with keyhole limpet haemocyanin (KLH) or from mice undergoing an acute graft vs host reaction (GVHR) was very low, but could be markedly increased by T cell receptor (TCR) ligation. This suggested that in vivo levels of lymphokine production are much lower than those induced by in vitro stimulation. Serum lymphokine titres were consistent with this possibility, and analysis of lymphokine mRNA levels using S1-nuclease protection demonstrated that in vitro-stimulated cells from normal, KLH and GVHR mice all had markedly increased levels of lymphokine transcripts relative to levels found in vivo. A novel method combining limiting dilution analysis with polymerase chain reaction amplification of cDNA was developed that showed that these differences in levels of lymphokine production were due at least in part to differences in the frequencies of lymphokine mRNA-containing cells. Studies of the means by which differential lymphokine production is achieved demonstrated that CD4+, CD8+ and cytotoxic T lymphocyte (CTL) clones all express a common, restricted set of lymphokines in response to a defined in vitro stimulus, but that individual in vivo primed cells can express at least seven distinct patterns of lymphokine production.

Animals↗
PubMed1992

Co-engagement of CD3 with LFA-1 or ICAM-1 adhesion molecules enhances the frequency of activation of single murine CD4+ and CD8+ T cells and induces synthesis of IL-3 and IFN-gamma but not IL-4 or IL-6.

Interaction between the cell adhesion molecules lymphocyte function-associated antigen-1 (LFA-1) and intercellular adhesion molecule-1 (ICAM-1) augments T cell activation by increasing the avidity of T cell/antigen-presenting cell (APC) binding. To examine whether LFA-1 and ICAM-1 can also contribute to T cell activation in the absence of APCs, single murine CD4+ and CD8+ T cells were cultured with IL-2 and immobilized antibodies to CD3, CD4 or CD8, and LFA-1 or ICAM-1. The combination of anti-CD3, anti-CD4/CD8, and IL-2 stimulated approximately 20% of CD4+ cells and 30% of CD8+ cells to proliferate. Inclusion of anti-ICAM-1 antibody increased these frequencies to 30 and 40% respectively. Maximum activation frequencies were obtained with the combination of anti-CD3, anti-CD4/CD8, and anti-LFA-1 which stimulated cell division by approximately 40% of single CD4+ cells and at least 60% of single CD8+ cells. Under these conditions, 30-40% of the resultant CD4+ clones and greater than 90% of CD8+ clones secreted IL-3 and IFN-gamma. In addition to responding at higher frequencies that CD4+ cells, CD8+ cells formed larger clones which produced 4-fold higher levels of both cytokines. Although the expression of IL-2, IL-3, IFN-gamma, granulocyte-macrophage colony stimulating factor and tumor necrosis factor alpha could be detected in CD4+ and CD8+ clones at the mRNA level following reverse transcription and polymerase chain reaction amplification, neither the secreted nor mRNA expression of IL-4 or IL-6 was detected in any of the tested clones. It is concluded that co-stimulation of T cells via LFA-1 or ICAM-1 can enhance T cell receptor-dependent activation in the absence of accessory cells and that this mode of stimulation leads to the expression of a restricted range of cytokine genes.

Animals↗
PubMed1992

Survival of the myeloid progenitor cell line FDC-P1 is prolonged by interferon-gamma or interleukin-4.

Continuous proliferation of the immortalized myeloid progenitor cell line FDC-P1 depends on stimulation with either interleukin-3 (IL-3) or granulocyte-macrophage colony stimulating factor (GM-CSF). Two other cytokines, interferon-gamma (IFN-gamma) and IL-4, were found to prolong FDC-P1 survival for several days. Surviving cells incorporated [3H]thymidine and a minority completed up to 3 cell divisions before dying. This transient proliferative response was a direct effect of IFN-gamma and IL-4 since these cytokines did not induce production of detectable IL-3 or GM-CSF and the response was unaffected by cell concentration. IL-6, a constitutive product of FDC-P1 cells whose secretion was increased by IL-3, GM-CSF and IL-4 but not by IFN-gamma, was not responsible for the proliferative response. FDC-P1 lines that constitutively expressed the cell cycle-associated oncogene myc or the survival-associated oncogene bcl-2 also responded only transiently to IFN-gamma or IL-4, indicating that expression of these genes did not complement the signals delivered by IFN-gamma or IL-4. By contrast, the protein kinase C activator phorbol 12-myristate 13-acetate (PMA) prolonged survival of FDC-P1 cells on its own and potentiated the response to IFN-gamma or IL-4, although the combination of stimuli did not support long-term growth. It is concluded that IFN-gamma and IL-4 trigger only some of the signalling events that lead to mitogenesis; these events are complemented by stimulation with PMA but additional signals are required for sustained proliferation.

Animals↗
PubMed1991

High-frequency activation of single CD4+ and CD8+ T cells to proliferate and secrete cytokines using anti-receptor antibodies and IL-2(1).

A high cloning efficiency single-cell culture system was developed to define the activation requirements of isolated CD4+ and CD8+ T cells to proliferate and secrete cytokines. T cells were triggered using solid-phase anti-CD3 and anti-CD4 or anti-CD8 antibodies plus rIL-2. Activation was measured by microscopic scoring of proliferation and by measurement of cytokine production using the cytokine-responsive cell lines FDC-P1, which responds to GM-CSF, IL-3, IFN-gamma and IL-4, and 32D clone 3 which responds to IL-3 only. Whilst anti-CD3 plus rIL-2 triggered only 4% of peripheral T cells to proliferate, anti-CD3 plus anti-CD8 mAb triggered about 40% of CD8+ T cells; 80% of the resultant clones secreted cytokine and 90% of these were IL-3+. Anti-CD3 plus anti-CD4 mAb triggered proliferation in about 20% of CD4+ T cells, of which 34% formed cytokine-producing clones with 47% of these secreting IL-3. In addition to responding at higher frequency, CD8+ T cells formed larger clones which produced higher levels of cytokines than CD4+ cells. Cell separation on the basis of Pgp-1 expression suggested that this culture system did not select for previously activated cells. Whereas Pgp-1+ T cells from keyhole limpet haemocyanin (KLH)-primed mice were enriched in KLH-specific cells, no significant differences were observed in the clonogenicity or cytokine-secreting capacity of Pgp-1+ and Pgp-1- T cells from normal mice.

Animals↗
PubMed1991

Heterogeneity in lymphokine profiles of CD4+ and CD8+ T cells and clones activated in vivo and in vitro.

Analysis of lymphokine mRNA expression and protein secretion by about 100 short-term alloreactive T-cell clones revealed marked heterogeneity in the combinations of lymphokines synthesized. This finding argues against a simple model in which T cells express either an unrestricted (Th0) or a restricted (Th1 or Th2) lymphokine profile. Lymphokine titers appeared to be normally distributed, with the percentage of positive clones for any one product determined by the threshold of detection. Accordingly, the observation that CD4+ clones on average produced higher titers of most lymphokines than CD8+ clones indicated that apparent differences between the lymphokine profiles of these two subsets were quantitative rather than qualitative. Patterns of lymphokine gene expression detected in whole tissues or by analysis of single cells and clones were markedly influenced by in vivo priming. Relative levels of expression of IL-4, IFN-gamma and GM-CSF in lymphoid tissues differed in mice undergoing a GvHR or following contact sensitization with OX or immunization with KLH in adjuvant. Consistent with the finding that IL-4 was the major lymphokine mRNA detected in lymph nodes of KLH-primed mice, most short-term KLH-specific clones derived from such mice also expressed IL-4. A similar approach to the detection of lymphokine-secreting T-cell precursors activated late in L. major infection showed that most clones from the L. major-resistant strain, C57BL/6, secreted IFN-gamma without IL-4 whereas most clones from the susceptible strain, BALB/c, secreted IL-4 without IFN-gamma. Differences were also noted in anti-CD3-induced IL-3 production at the single-cell level between CD8+ cells activated in the GvHR or against a tumor allograft. Con A-induced, filler cell-dependent cloning of CD4+ T cells from unprimed mice gave rise both to IFN-gamma-producing and to IL-4-producing clones. A requirement for an undefined, filler cell-dependent signal for development of IL-4-secreting clones was suggested by the finding that clones of normal CD4+ and CD8+ T cells activated in an anti-CD3-induced, filler cell-free system exclusively produced IFN-gamma and IL-3 without detectable IL-4 or IL-6. With a view to developing a single-cell approach to the analysis of lymphokine profiles of in vivo-activated T cells, sensitive assays for IL-3 and other lymphokines were used to measure secreting cells activated in the GvHR or against a tumor allograft.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1990

Frequency analysis of lymphokine-secreting CD4+ and CD8+ T cells activated in a graft-versus-host reaction.

Lymphokine secretion by in vivo-activated T cells was analyzed at the population and single-cell levels in lymphocytes from mice undergoing an acute allogeneic graft-vs-host reaction (GVHR). Three observations were made. First, constitutive lymphokine production by these cells was very low but could be dramatically up-regulated by TCR ligation. Thus, even when harvested at the peak of the GVHR, fewer than 0.1% of lymphocytes secreted detectable granulocyte-macrophage (GM)-CSF, IFN-gamma, or IL-3 in the first 24 h in vitro, and average production of these lymphokines in bulk cultures was less than 10(-5) U/cell. However, when cultured for 24 h with anti-CD3 antibody under conditions which activated less than 0.1% of normal cells, about 30% of GVHR T cells secreted GM-CSF, IFN-gamma, and/or IL-3, and average production levels were increased by 10(3)- to 10(4)-fold. Together with evidence that host alloantigen-induced lymphokine secretion was 10 to 100 times lower than the anti-CD3 response, these data suggest that physiologic lymphokine synthesis by most T cells is low (less than 10(-18) mol of IL-3 per cell) but can be raised above the threshold of detection by TCR cross-linking. Second, individual GVHR lymphocytes varied markedly in their total and relative production of different lymphokines in response to anti-CD3 stimulation, with some cells secreting IL-3 alone, some secreting IL-3 accompanied by other lymphokines (GM-CSF and/or IFN-gamma), and some secreting other lymphokines without detectable IL-3. Finally, both CD4+ and CD8+ T cells from GVHR mice responded to anti-CD3 antibody by secreting IL-3 and other lymphokines: purified CD4+ cells contained an average of 16% and CD8+ cells an average of 10% anti-CD3-inducible lymphokine-secreting cells. By contrast, only 2 to 3% of cells of either subset formed clones in cultures with host allogeneic cells and IL-2, suggesting that clonogenic alloreactive cells were a minority of the T cells activated in the GVHR.

Animals↗
PubMed1990

Abrogation of the requirement for feeder cell interaction and T cell receptor stimulation of lymphocytes infected with retroviral vectors.

Infection of sensitive adult mice with myeloproliferative sarcoma virus (MPSV) results in a myeloproliferative syndrome. Two components of the viral genome are required to induce this unique pathology: the mos oncogene and sequences within the U3 region of the long terminal repeat (LTR). In studies designed to identify the target cell of MPSV and thus better understand the mechanism by which a myeloproliferative syndrome is induced, we have infected a series of T cell lines with MPSV-based vectors. The results presented here show that infection with neoR MPSV abrogates the requirement for an antigen-specific or feeder cell-dependent stimulation, without altering the requirement for interleukin 2. Significantly, this response is not dependent on the mos oncogene, but requires sequences within the U3 region of the MPSV LTR. No alteration in the constitutive or induced levels of lymphokines released by these cells was observed. These results suggest a model in which T cells acquire a proliferative advantage by uncoupling the proliferative response from the lymphokine synthesis that is induced by activation of the T cell receptor. These cells are thus poised for antigen stimulation and secretion of cytokines that stimulate myelopoiesis.

Cell Line↗