Murine T helper cell clones secrete granulocyte-macrophage colony-stimulating factor (GmCSF) by both interleukin-2-dependent and interleukin-2-independent pathways

Granulocyte-macrophage colony-stimulating factor (GmCSF) is a lymphokine secreted by class II major histocompatibility complex (MHC)-restricted T cells after lectin or antigen stimulation. To investigate the relationship between interleukin-2 (IL-2) and GmCSF production, we utilized long-term cultures of porcine myelin basic protein (PMBP)-specific T helper cell clones that were maintained with IL-2 in the absence of antigen or irradiated antigen-presenting cells (APC). We have found that supernatants of these T cell clones contained GmCSF activity after IL-2 stimulation. Inhibition of cell proliferation by irradiation failed to stop GmCSF production. When these clones were stimulated with PMBP and irradiated APC in the presence of anti-IL-2 receptor antibody, the T cell supernatants still contained GmCSF activity. These results indicate that (1) GmCSF production by T helper clones after IL-2 stimulation is independent of cell proliferation and (2) antigen/MHC-stimulated GmCSF production by T cell clones can occur by an IL-2-independent pathway.     

Identification of IL-6 as a T cell-derived factor that enhances the proliferative response of thymocytes to IL-4 and phorbol myristate acetate

Thymocytes undergo a vigorous proliferative response when stimulated with a combination of IL-4 and PMA. We have found that conA-induced supernatants from a number of Th cell clones could enhance the level of IL-4/PMA-induced proliferation of unseparated thymocytes 0.5- to 2-fold and of peanut agglutinin-positive thymocytes 2- to 10-fold. These supernatants did not contain IL-2 or IFN-gamma, and the enhancing activity could be chromatographically separated from IL-3, -4, -5, and granulocyte/macrophage CSF. The possibility that the thymocyte enhancement factor contained in these supernatants was IL-6 was suggested when murine rIL-6 was found to have similar activity. Further evidence for the identity of these two factors was obtained when an IL-6 assay, based on plasmacytoma growth, was used to test column fractions showing thymocyte enhancement. All fractions active in the thymocyte enhancement assay also had activity in the plasmacytoma growth assay. These observations suggest that the thymocyte-stimulating activity present in the T cell supernatants was due to IL-6.     

Virus-induced interferon alpha/beta (IFN-alpha/beta) production by T cells and by Th1 and Th2 helper T cell clones: a study of the immunoregulatory actions of IFN-gamma versus IFN-alpha/beta on functions of different T cell populations

Spleen cells, resting T cells, activated T cells, and T cell clones characterized as type 1 (Th1) and type 2 (Th2) were investigated for their ability to produce interferon (IFN) following in vitro culture with Newcastle disease virus (NDV). All of the above cell populations, including both Th1 and Th2 T cell clones, produced high levels of IFN following in vitro culture with NDV. This IFN was characterized as a mixture of IFN-alpha and IFN-beta with IFN-alpha being the predominate species of IFN contained in the mixture. IL-2 greatly enhanced the production of IFN-alpha/beta by all cell populations in response to NDV. These different T cell populations responded very differently to the immunoregulatory actions of IFN-gamma versus IFN-alpha/beta. IFN-alpha/beta was shown to be a potent inhibitor of Con A or IL-2-induced proliferation of different T cell populations. This inhibition was not associated with a reduction in lymphokine production since spleen cells or Th1 T cell clones cultured with Con A and IFN-alpha/beta had no decrease in IL-2 or IFN-gamma production when compared to Con A-stimulated control cultures. IFN-gamma had little to no inhibitory activity on Con A-induced proliferation of spleen cells. In fact, Con A-induced proliferation was usually enhanced by IFN-gamma when nylon wool-enriched T cells were assessed. Different results were observed when IFN-gamma and IFN-alpha/beta were investigated for their ability to inhibit IL-2-induced proliferation of different T helper cell clones. IFN-gamma and IFN-alpha/beta were both capable of inhibiting IL-2-induced proliferation of T cell clones characterized as type 2 (Th2). In contrast, IFN-gamma had no effect on IL-2-induced proliferation of Th1 clones. IFN-alpha/beta, however, inhibited IL-2-induced proliferative responses of both Th1 and Th2 T cell clones. These results document the facts that (1) IFN-gamma and IFN-alpha/beta differ in their immunoregulatory actions, (2) different T cell subpopulations vary in their susceptibility to IFN-gamma regulation, and (3) virus induction of IFN-alpha/beta appears to be a ubiquitous function associated with different T cell populations.     

Membranes from both Th1 and Th2 T cell clones stimulate B cell proliferation and prepare B cells for lymphokine-induced differentiation to secrete Ig.

Plasma membranes from the mitogen-activated mouse Th2 cell clone D10.G4.1 have recently been shown to provide the cell contact-dependent signals necessary for the induction of small B cell proliferation. Together with the Th2-derived lymphokines IL-4 and IL-5, these membranes stimulate production of Ig isotypes identical to those produced when B cells were stimulated by intact Th2 cells. In contrast, Th1 clones are poor inducers of Ig production in vitro. This could be solely due to differences in the lymphokines released by Th1 and Th2 cells or to differences in the cell-cell contact signals delivered by activated Th1 and Th2 cells. We report that membranes from three different activated Th1 clones induced strong Ag-independent proliferation of small dense B cells. The level of B cell proliferation was enhanced approximately fourfold by the addition of lymphokine-containing supernatant from Con A-activated Th2 cells and was unaffected by any of the lymphokine-containing supernatants from Con A-activated Th1 clones. As with D10.G4.1 membranes, Th1 membranes alone induced B cell proliferation but not secretion of Ig. However, addition of supernatant from Con A-activated D10.G41 cells, but not any supernatants from Con A-activated Th1 cells, induced Ig secretion of all isotypes. These effects were shown to not simply result from increased B cell numbers after stimulation with Th2 lymphokines. Thus, Th1 cell clones seem to poorly induce antibody responses entirely because of their lymphokine repertoire and not because of differences or deficiencies in the ability of these cells to deliver cell contact-dependent signals to B cells.     

Anti-proliferative effect of IFN-gamma in immune regulation. II. IFN-gamma inhibits the proliferation of murine bone marrow cells stimulated with IL-3, IL-4, or granulocyte-macrophage colony-stimulating factor

A biphasic dose response curve was observed when the bone marrow-derived cell line FDCP1, used as an indicator line for IL-3 bioassays, was exposed to supernatants from some activated T cell clones but not others. The active component which inhibited proliferation at the higher supernatant concentrations appeared to be IFN-gamma, based on the following observations. 1) Only those culture supernatants which contained IFN-gamma gave a biphasic dose response curve; 2) with these supernatants, an anti-IFN-gamma mAb augmented the proliferation of FDCP1 cells at the higher supernatant concentrations; and 3) rIFN-gamma profoundly inhibited the proliferation of FDCP1 cells stimulated with rIL-3 or rIL-4. rTNF-alpha inhibited FDCP1 proliferation only to a modest extent, yet the combination of rTNF-alpha + rIFN-gamma provided greater inhibition than each agent alone. The proliferation of a second bone marrow-derived cell line, DA1, was not inhibited by rIFN-gamma or rIFN-gamma + rTNF-alpha when stimulated with rIL-3 or recombinant granulocyte-macrophage colony-stimulating factor (rGM-CSF). Fresh bone marrow cells also showed a suboptimal proliferative response when stimulated with T cell supernatants containing IFN-gamma, and this response was augmented considerably upon the addition of anti-IFN-gamma mAb. Bone marrow cell proliferation was observed upon exposure to rIL-3, rIL-4, or rGM-CSF, and these responses were inhibited by rIFN-gamma; rTNF-alpha also produced a synergistic effect with these cells. Bone marrow cell colony formation stimulated by rIL-3 or rGM-CSF also was inhibited by rIFN-gamma. Colony formation in bone marrow cell cultures was not observed in response to rIL-4. Collectively, these results suggest that Th1 cells, which in addition to IL-3 and GM-CSF also produce IFN-gamma, may regulate hemopoietic cell proliferation and colony formation differently from the way Th2 cells do, which do not produce IFN-gamma.     

Antiproliferative effect of IFN-gamma in immune regulation. III. Differential selection of TH1 and TH2 murine helper T lymphocyte clones using recombinant IL-2 and recombinant IFN-gamma

Supernatants collected after primary or secondary stimulation of spleen cells contain different arrays of lymphokines. Primary supernatants from spleen cells stimulated with Con A or allogeneic spleen cells (MLC-SF) contain IL-2 but little IL-4 or IGN-gamma; in contrast, secondary MLC-SF contains IL-2 as well as substantial IL-4 and IFN-gamma. Our laboratory previously had always used secondary MLC-SF for cloning T cells, and had routinely obtained TH1 helper T lymphocyte clones. In the present study, when primary Con A-SF was used as source of growth factors, TH2 and not TH1 clones were preferentially derived. Considering the possibility that IFN-gamma may be one important factor in determining whether TH1 or TH2 clones are preferentially obtained, clone derivation was then performed either in the presence of rIL-2 or rIL-2 plus rIFN-gamma. The majority of clones derived using rIL-2 alone were TH2 cells, whereas the majority of clones derived using rIL-2 plus rIFN-gamma were TH1 cells. Using either procedure, some clones were obtained that produced IL-2, IL-4, and IFN-gamma. These data are consistent with our previous observations that IFN-gamma inhibits the proliferation of TH2 but not TH1 clones, and suggest that the presence of IFN-gamma during an immune response would result in the preferential expansion of helper T lymphocytes of the TH1 phenotype. Our procedure for the differential selection of TH1 and TH2 clones reactive with the same Ag should be useful for designing in vitro systems for studying the function of these cell subsets in specific immune responses.     

A role for L3T4+ T cells and their lymphokines in the generation of suppressor effector (TS3) cells

The cellular requirements for the in vitro induction of antigen-specific suppressor T cells were examined. Previous reports indicated that Ia-bearing macrophages and anti-idiotypic B cells are required as accessory cells to facilitate the generation of suppressor effector (TS3) cells which regulate the response to the 4-hydroxy-3-nitrophenyl acetyl (NP) hapten. The present study describes two distinct T cell populations which interact to generate antigen-specific TS3. Fractionation of the T cell populations with monoclonal antibody to the L3T4 determinant led to the identification of an NP-specific L3T4- TS3 progenitor population and an L3T4+ helper/inducer subset. In the presence of NP-coupled antigen, the L3T4+ subset could induce progenitor TS3 to differentiate into mature TS3 cells. The activity of the L3T4+ inducer population could be replaced with specifically activated cloned helper cells which were not NP-reactive since an I-Ab-restricted, insulin-reactive, L3T4+ clone was capable of supporting the generation of NP-specific TS3. Inducer activity appeared to be confined to the Th1 but not the Th2 subset. In addition, 18-hr supernatants from antigen-activated clones were capable of substituting for L3T4+ cells or T cell clones in TS3 induction cultures. The TS maturation/differentiation factor(s) active in these supernatants does not appear to be IL-1, IL-2, IL-3, or interferon-gamma alone since purified sources of these lymphokines failed to induce TS3 activity.     

Tumor necrosis factor-alpha as a proliferative signal for an IL-2-dependent T cell line: strict species specificity of action

The ability of TNF-alpha to stimulate T cell proliferation was examined. We demonstrate that murine rTNF-alpha induces the proliferation of CT6, a murine T cell line previously thought to be responsive only to IL-2. This activity appears to be the result of the direct action of murine rTNF-alpha on the CT6 cells because neither 1) murine IL-2 or murine IL-4, lymphokines also capable of inducing CT6 proliferation, were detected in culture supernatants from murine rTNF-alpha-treated CT6 cells nor 2) did antibodies specific for IL-2 or IL-4 inhibit murine rTNF-alpha-induced CT6 proliferation. Unlike many of the activities displayed by TNF-alpha, its ability to induce CT6 cell proliferation shows strict species specificity as indicated by the failure of human rTNF-alpha to stimulate these cells. Flow cytometric analysis and binding of radiolabeled TNF-alpha have indicated that receptors for TNF-alpha on these cells are specific for murine TNF-alpha. The ability of murine rTNF-alpha to induce the proliferation of certain T cell lines further indicates that this molecule plays an important role in regulation of T cell-mediated immune responses.     

Modulation of IL-2- and IL-4-induced cytotoxicities in human T helper lymphocyte clones by tumor necrosis factor-alpha.

A set of alloreactive IL-2-dependent human CD4+ 45RA-w29+56- Th cell clones was divided into two groups according to their ability to respond to IL-4 by proliferation and their susceptibility to inhibition by TNF-alpha. The latter cytokine blocked proliferative responses to IL-2 of IL-4-nonresponsive clones, but did not affect proliferation of IL-4-responsive clones. In the present communication, it is demonstrated that exposure of apparently non-cytotoxic Th cells to IL-4 resulted in the dose-dependent induction of allospecific CTX in clones previously shown to be capable of responding to IL-4 by proliferation. In contrast, IL-2 induced both allospecific and MHC-unrestricted "NK-like" CTX in both IL-4 responder and nonresponder TCC. However, coculture with IL-4 in addition to IL-2 down-regulated this induction of NK-like CTX by the IL-2 (in those clones capable of responding to IL-4). Acquisition of these two types of CTX by the same TCC was additionally modulated by TNF-alpha, which also blocked the induction of NK-like CTX but had no effect on the induction of allospecific CTX by either IL-2 or IL-4. In contrast, IFN-gamma was unable to block induction of either type of CTX in this model system. These data suggest that even at the clonal level, the relative availability of a number of different up- and down-regulatory cytokines influences the outcome of an immune response. In the present model, IL-2 up-regulates specific and NK-like CTX, the latter component of which is down-regulated by TNF-alpha or IL-4, whereas IL-4 itself can up-regulate specific but not NK-like CTX.     

IL-4-responsive human helper T cell clones are resistant to growth inhibition by tumor necrosis factor-alpha

Positive and negative signals for clonal expansion of preactivated human CD4+ alloreactive Th cells have been examined. Fifteen T cell clones tested 3 days after Ag-specific stimulation proliferated with IL-2 but only five of these responded to IL-4. The remaining 10 also failed to respond to IL-4 in the presence of IL-1 and/or autologous B-LCL. The response of the latter five to IL-4 was independent of IL-2 as shown by the inability of IL-2R mAb to prevent proliferation. In contrast, transferrin R mAb blocked responses to both IL-2 and IL-4. IL-4 responder but not nonresponder clones demonstrated IL-4-enhanced responses to suboptimal concentrations of IL-2 (1 U/ml), but none of the clones showed enhanced responses with 1 U/ml IL-2 plus IL-1, IL-3, IL-5, or granulocyte-macrophage-CSF. IFN-gamma did not enhance or inhibit responses to either IL-2 or IL-4. TNF-alpha did not block proliferation supported by IL-4. In contrast, TNF-alpha did block proliferative responses to IL-2, but only by those clones which were incapable of responding to IL-4. Thus, proliferation of the IL-4-responder clones was not blocked by TNF-alpha when optimal or even supraoptimal concentrations of IL-2 were used as growth factor. Because all T cell clones themselves secreted TNF-alpha after specific stimulation, these results suggest a novel autocrine negative regulatory pathway, whereby IL-4-reactive helper cells would have a selective advantage over IL-4-nonreactive cells during the evolution of an immune response.     

Development and characterization of interleukin-2-independent antigen-specific human T cell clones that produce multiple lymphokines

The development of antigen-specific T lymphocyte lines and clones has greatly facilitated the investigation of T-cell recognition of and response to foreign antigens. In the present study, human antigen-specific helper T cell lines and clones which are completely independent of exogenous interleukin-2 (IL-2) have been developed by cyclic restimulation with the soluble antigen keyhole limpet hemocyanin (KLH) to which the T cell donor had previously been immunized. These T cells uniformly bear the OKT4 phenotype and were shown to require both histocompatible antigen-presenting cells (APC) and antigen for optimal proliferation. The T cell line was composed of a highly antigen-specific and clonable T cell population. Following four cycles of antigen stimulation, limiting dilution cloning analysis showed a Poisson distribution of clonable T cells with a precursor frequency of 0.62, and from 88 to 92% of viable clones were specific for the stimulating antigen. Individual clones were obtained which recognized KLH with either DR 1 (one parental Ia haplotype of the donor) or DR 2 (the other parental Ia haplotype) allogeneic APC, but not both. Following stimulation with KLH, the T cell clones produced IL-2. Peak amounts of IL-2 were assayable in the first 6 to 24 hr after stimulation. In contrast, virtually no IL-2 was detectable in supernatants at 72 to 96 hr, suggesting autoutilization by the proliferating T cells. In addition, some clones were also capable of producing both B cell growth factor and IL-2 following KLH stimulation. These IL-2-independent T cells appeared to be derived from a discrete Leu 8-negative subclass of T4⁺ cells and expressed the full complement of Ia antigen of the donor. Thus, soluble antigen-specific human helper T cell clones have been produced which can be maintained in the absence of exogenous IL-2, elaborate their own growth factors and other immunoregulatory lymphokines, and show fine DR-related restriction to either one or the other parental DR haplotypes in antigen-stimulated proliferative responses.     

IL-2 secretion by soluble antigen-reactive human T-cell clones

Human tetanus toxoid specific T-cell lines and clones capable of producing IL-2 were established. IL-2 production occurred only when the antigen-specific T cells were cultured with both tetanus toxoid antigen and an autologous, irradiated adherent cell population. The T-cell lines and clones remained strictly dependent on exogenous IL-2 for proliferation at all other times. Phenotypic characterization with monoclonal antibodies recognizing T-cell subsets revealed that the antigen-specific lines and clones bore predominantly OKT3 and OKT4 markers with essentially no OKT8 positive cells present. T-cell clones which were demonstrated to secrete IL-2 activity could also partially deplete media of IL-2 if cultured in the absence of soluble antigen and irradiated adherent cells.     

Pertussis toxin by inducing IL-6 promotes the generation of IL-17-producing CD4 cells

Compelling evidence has now demonstrated that IL-17-producing CD4 cells (Th17) are a major contributor to autoimmune pathogenesis, whereas CD4+CD25+ T regulatory cells (Treg) play a major role in suppression of autoimmunity. Differentiation of proinflammatory Th17 and immunosuppressive Treg from naive CD4 cells is reciprocally related and contingent upon the cytokine environment. We and others have reported that in vivo administration of pertussis toxin (PTx) reduces the number and function of mouse Treg. In this study, we have shown that supernatants from PTx-treated mouse splenic cells, which contained IL-6 and other proinflammatory cytokines, but not PTx itself, overcame the inhibition of proliferation seen in cocultures of Treg and CD4+CD25- T effector cells. This stimulatory effect could be mimicked by individual inflammatory cytokines such as IL-1beta, IL-6, and TNF-alpha. The combination of these cytokines synergistically stimulated the proliferation of CD4+CD25- T effector cells despite the presence of Treg with a concomitant reduction in the percentage of FoxP3+ cells and generation of IL-17-expressing cells. PTx generated Th17 cells, while inhibiting the differentiation of FoxP+ cells, from naive CD4 cells when cocultured with bone marrow-derived dendritic cells from wild-type mice, but not from IL-6-/- mice. In vivo treatment with PTx induced IL-17-secreting cells in wild-type mice, but not in IL-6-/- mice. Thus, in addition to inhibiting the development of Treg, the immunoadjuvant activity of PTx can be attributable to the generation of IL-6-dependent IL-17-producing CD4 cells.     

Activated self-MHC-reactive T cells have the cytokine phenotype of Th3/T regulatory cell 1 T cells

In the present study, we show that human self-MHC-reactive (autoreactive) T cell clones are functionally distinct from Ag-specific T cell clones. Self-MHC-reactive T cells exhibited helper function for B cell Ig production when cultured with non-T cells alone, and they exhibit suppressor function when cultured with PWM- or rCD40 ligand (rCD40L)-activated non-T cells, whereas tetanus toxoid (TT)-specific clones exhibited only helper function in the presence of TT with or without PWM or rCD40L. Addition of neutralizing Abs to the cultures showed that the suppression was mediated by TGF-beta but not by IL-10 or IFN-gamma. The self-MHC-reactive clones also inhibited proliferation of primary CD4+ T cells and TT-specific T cell clones, but in this case the inhibition was mediated by both IL-10 and TGF-beta. In further studies, the interactions between self-MHC-reactive T cell clones and non-T cells that led to suppressor cytokine production have been explored. We found that prestimulation of non-T cells for 8 h with PWM or for 48 h for rCD40L results in non-T cells capable of inducing self-MHC-reactive T cell to produce high levels of TGF-beta and IL-10. In addition, these prestimulation times coincided with peak induction of HLA-DR and costimulatory B7 molecule (especially CD86) expression on B cells. Finally, addition of CTLA-4/Fc or blocking F(ab')2 anti-CTLA-4 mAb, plus optimally stimulated non-T cells, to cultures of self-MHC-reactive clones inhibited the induction of TGF-beta but not IL-10 or IFN-gamma production. In summary, these studies show that activated self-MHC-reactive T cells have the cytokine phenotype of Th3 or T regulatory cell 1 and thus may be important regulatory cells that mediate oral and peripheral tolerance and prevent the development of autoimmunity.     

Role of uncultured human melanoma cells in the proliferation of autologous tumor-specific cytotoxic T lymphocytes.

The role of uncultured melanoma cells in the proliferation of autologous tumor-specific cytotoxic T lymphocytes (CTLs) was investigated. Uncultured autologous tumor cells by themselves induced modest, but significant, proliferation in 10 of 13 (77%) CTL clones and in only two of nine non-CTL clones. Uncultured allogenic melanoma cells mostly failed to induce CTL proliferation. Autologous tumor-induced CTL proliferation declined with increasing age of the culture. It did not correlate with IL-2 receptor-alpha expression or was not inhibited by addition of anti-IL-2 antibody to the culture. It was inhibited by pretreatment of tumor cells with anti-MHC class II, but not -MHC class I mAb. IL-2 alone was sufficient for the potent proliferation of five of nine CTL clones. In all these five CTL clones, autologous tumor cells suppressed IL-2-induced proliferation. The remaining four CTL clones, however, required both uncultured autologous melanoma cells and IL-2 for the proliferation. IL-4 or IL-6, in particular IL-6, facilitated IL-2-induced CTL proliferation, but not their cytotoxicity. In summary, uncultured melanoma cells by themselves induced modest levels of CTL proliferation in the context of MHC class II antigens, whereas they suppressed IL-2-induced CTL proliferation in more than half of the clones.     

The spliceosomal autoantigen heterogeneous nuclear ribonucleoprotein A2 (hnRNP-A2) is a major T cell autoantigen in patients with systemic lupus erythematosus

A hallmark of systemic lupus erythematosus (SLE) is the appearance of autoantibodies to nuclear antigens, including autoantibodies directed to the heterogeneous nuclear ribonucleoprotein A2 (hnRNP-A2), which occur in 20% to 30% of SLE patients as well as in animal models of this disease. To investigate the underlying cellular reactivity and to gain further insight into the nature and potential pathogenic role of this autoimmune response we characterized the T cell reactivity against hnRNP-A2 in patients with SLE in comparison to healthy controls. Cellular proliferation of peripheral blood T cells to hnRNP-A2 was determined by [3H]thymidine incorporation and T cell clones (TCCs) specific for hnRNP-A2 were grown by limiting dilution cloning; IFNγ, IL-4 and IL-10 in culture supernatants were measured by ELISA. Bioactivity of culture supernatants was determined by incubation of anti-CD3/anti-CD28 stimulated peripheral blood CD4+ T cells with supernatants of TCCs. Stimulation assays performed with peripheral blood mononuclear cells of 35 SLE patients and 21 healthy controls revealed pronounced proliferative responses in 66% of SLE patients and in 24% of the controls, which were significantly higher in SLE patients (p < 0.00002). Furthermore, hnRNP-A2 specific TCCs generated from SLE patients (n = 22) contained a relatively high proportion of CD8+ clones and mostly lacked CD28 expression, in contrast to TCCs derived from healthy controls (n = 12). All CD4+ TCCs of patients and all control TCCs secreted IFNγ and no IL-4. In contrast, CD8+ TCCs of patients secreted very little IFNγ, while production of IL-10 did not significantly differ from other T cell subsets. Interestingly, all CD8+ clones producing IL-10 in large excess over IFNγ lacked expression of CD28. Functional assays showed a stimulatory effect of the supernatants derived from these CD8+CD28- hnRNP-A2 specific TCCs that was similar to that of CD4+CD28+ clones. Taken together, the pronounced peripheral T cell reactivity to hnRNP-A2 observed in the majority of SLE patients and the distinct phenotype of patient-derived CD8+ TCCs suggest a role for these T cells in the pathogenesis of SLE.     

Central role for TCR/CD3 ligation in the differentiation of CD4+ T cells toward A Th1 or Th2 functional phenotype.

Activated CD4+ T cells can be classified into distinct subsets; the most divergent among them may be considered to be the IL-2 and IFN-gamma-producing Th1 clones and the IL-4 and IL-5-producing Th2 clones. Because Th1 and Th2 clones can usually be detected only after several months of culture, we used conditions that modulate the IL-2 and IL-4 production in short term culture. Here we show that freshly isolated and subsequently in vitro-activated CD4+ T cells that were cultured for 11 days with rIL-2 and restimulated showed a IFN-gamma+ IL-2+ IL-3+ IL-4- IL-5- pattern. Because these cells were not capable of providing B cell help for IgG1, IgG2a, or IgE in an APC- and TCR-dependent T-B cell assay, they expressed a phenotype typical for most Th1 clones. In contrast, activated T cells that were cultured for 11 days with IL-2 plus a mAb to CD3 and then restimulated produced a IFN-gamma- IL-2- IL-3+ IL-4+ IL-5+ pattern. These cells were capable of providing B cell help for IgG1, IgG2a, and IgE synthesis and thus presented a phenotype typical for Th2 clones. Similar results were observed when mitogenic mAb to Thy-1.2 or to framework determinants of the alpha beta TCR were used. The induction of Th1- and Th2-like cells did not depend on the relative expression of CD44 or CD45 by the T cells before activation in vitro. Because the incubation of activated T cells with anti-CD3/TCR mAb induced high unrestricted lymphokine production, the latter might be responsible for the Th2-like lymphokine pattern observed after restimulation. To address this point, TCR V beta 8+ and V beta 8- T cell blasts were co-cultured in the presence of mAb to V beta 8. After restimulation, V beta 8+ cells had a IL-4high IL-2low phenotype and V beta 8- cells had a IL-4low IL-2high phenotype. This demonstrates that TCR ligation but not lymphokines alone are capable of inducing Th2-like cells, and this points out a central role for the TCR in the generation of T cell subsets.     

Secretion of colony-stimulating factors by T cell clones. Role in adoptive protection against Listeria monocytogenes

CSF have been postulated to be important mediators of host defenses. The current studies were undertaken to investigate the production of CSF by Listeria-specific, T cell clones and to assess the participation of CSF in anti-listerial host resistance. Listeria-specific L3T4+, Lyt-2- T cell clones were isolated and expanded by standard techniques. The clones themselves protected mice from listerial challenge when injected intravenously, and supernatants generated from Ag-stimulated clones were protective. In order to define factors important in the protection, supernatants from the clones were assayed for CSF by several in vitro assays. Total colony-stimulating activity was measured with a bone marrow colony-forming assay. T cell clones secreted 1000 to 2000 U/ml of colony-stimulating activity after 48 hours of stimulation with specific antigen. The relative amounts of the various CSF were determined by the capacity of supernatants to support proliferation of the factor-dependent cell lines FDCP-1 and 32D cl 3 in the presence and absence of specific anti-CSF antibodies. Results showed that most of the CSF activity was due to granulocyte-macrophage (GM)-CSF and IL-3. The role of GM-CSF in anti-listerial host resistance was assessed in two types of experiments. In one set of experiments GM-CSF activity was neutralized in the supernatants by addition of specific rabbit anti-GM-CSF antibodies. Treated and untreated supernatants were then tested for their capacity to protect nonimmune mice against listerial challenge. Neutralization of GM-CSF in the supernatants decreased the protective capacity of the supernatants by approximately 23%. In a second set of studies, the administration of recombinant murine GM-CSF was shown to protect mice from challenges of L. monocytogenes. Taken together, these experiments provide evidence that CSF are important mediators of immune T cell mediated host defenses.     

Th1-Induced CD106 Expression Mediates Leukocytes Adhesion on Synovial Fibroblasts from Juvenile Idiopathic Arthritis Patients

This study tested the hypothesis that subsets of human T helper cells can orchestrate leukocyte adhesion to synovial fibroblasts (SFbs), thus regulating the retention of leukocytes in the joints of juvenile idiopathic arthritis (JIA) patients. Several cell types, such as monocytes/macrophages, granulocytes, T and B lymphocytes, SFbs and osteoclasts participate in joint tissue damage JIA. Among T cells, an enrichment of classic and non-classic Th1 subsets, has been found in JIA synovial fluid (SF), compared to peripheral blood (PB). Moreover, it has been shown that IL-12 in the SF of inflamed joints mediates the shift of Th17 lymphocytes towards the non-classic Th1 subset. Culture supernatants of Th17, classic and non-classic Th1 clones, have been tested for their ability to stimulate proliferation, and to induce expression of adhesion molecules on SFbs, obtained from healthy donors. Culture supernatants of both classic and non-classic Th1, but not of Th17, clones, were able to induce CD106 (VCAM-1) up-regulation on SFbs. This effect, mediated by tumor necrosis factor (TNF)-α, was crucial for the adhesion of circulating leukocytes on SFbs. Finally, we found that SFbs derived from SF of JIA patients expressed higher levels of CD106 than those from healthy donors, resembling the phenotype of SFbs activated in vitro with Th1-clones supernatants. On the basis of these findings, we conclude that classic and non-classic Th1 cells induce CD106 expression on SFbs through TNF-α, an effect that could play a role in leukocytes retention in inflamed joints.