Mechanisms of eosinophilia in Toxocara canis infected mice: In vitro production of interleukin 5 by lung cells of both normal and congenitally athymic nude mice

Mechanisms of eosinophilia were compared between in vitro bone marrow cell cultures of congenitally athymic (nu/nu) mice and their heterozygous littermates (nu/+). Cultures of 5 × 10⁴ bone marrow cells using interleukin 3 (IL-3), IL-5 and granulocyte-macrophage colony-stimulating factor showed that nu/nu and nu/+ mice mimicked each other in eosinophil production both before and after infection with Toxocara canis. Eosinophil differentiating activity (EDA) was detected in media conditioned by spleen cells and lungs of T. canis infected nu/+ mice, although nu/nu mice showed EDA only in lung-conditioned medium. EDA, detected both in infected nu/nu and nu/+ mice, was inhibited by an anti-IL-5 monoclonal antibody. These results indicate that IL-5 may be produced by lung cells of both nu/nu and nu/+ mice as well as by spleen cells of nu/+ mice infected with T. canis, which is the reason why nu/nu mice infected with T. canis exhibit blood eosinophilia.     

Interleukin 12 is required for the T-lymphocyte-independent induction of interferon gamma by an intracellular parasite and induces resistance in T-cell-deficient hosts.

Immunity against the intracellular protozoan Toxoplasma gondii is highly dependent on interferon gamma (IFN-gamma). We have previously shown that, in addition to T lymphocytes, natural killer (NK) cells can be stimulated by the parasite to produce this cytokine by a reaction requiring adherent accessory cells and tumor necrosis factor alpha. We now demonstrate that a recently characterized cytokine, interleukin 12 (IL-12), is also necessary for parasite-induced IFN-gamma synthesis by NK cells. Anti-IL-12 antibodies completely inhibited T. gondii or bacterial endotoxin-stimulated IFN-gamma production by NK-enriched spleen cells from severe combined immunodeficient mice. Moreover, potent NK cytokine responses were induced by the combination of IL-12 and tumor necrosis factor alpha. In addition, adherent spleen cells from scid/scid mice or thyoglycollate-elicited macrophages from BALB/c animals produced high levels of both IL-12 (p40) and tumor necrosis factor alpha mRNAs when exposed to either live tachyzoites, parasite extracts, or endotoxin, confirming that these cytokines are produced by accessory cells. Finally, in vivo studies showed that treatment with recombinant IL-12 results in prolonged survival of scid mice after infection with T. gondii by means of a response dependent on both IFN-gamma and NK cells. Together the data argue that IL-12 is required for the T-cell-independent triggering of NK cells by intracellular parasites and that the cytokine may be useful for inducing this protective pathway in immunodeficient hosts.     

Interleukin 2 is mitogenic for nu/nu and nu/+ murine spleen cells.

Interleukin 2 (IL-2), a product of activated T lymphocytes but not of T-cell-deficient spleen cells of congenitally athymic (nu/nu) mice, is shown to be strongly mitogenic for spleen cells from both nu/nu and nu/+ mice in the absence of serum. This response does not depend on the presence of additional mitogen or antigen as has been previously reported and is dose dependent with respect to IL-2. Plots of the logarithm of cell number versus logarithm of response indicate that IL-2-induced mitogenesis of nu/nu spleen cells is a one-cell event (slope = 1.28 +/- 0.21, mean +/- SD), whereas the response of nu/+ spleen cells to concanavalin A is a three-cell event (slope = 3.18 +/- 0.16). The nu/nu spleen cells proliferating in response to IL-2 are at least 80% T lymphocytes by the third day of culture, as demontrated by lysis with monoclonal anti-Thy-1 antibody and complement. These results suggest that one of the major roles of the thymus may be to induce IL-2 production in a subpopulation of lymphocytes that is then persistent.     

Functional T cells in athymic nude mice.

After passage of spleen cells from nu/nu mice over a nylon wool column, concanavalin A-responsive cells can be detected in the presence of 2-mercaptoethanol, and specific cytotoxic T lymphocytes can be generated without exposure to interleukin 2 (IL-2). The spleen cells of the nu/nu mice born of nu/nu parents and nursed by nu/nu mothers had significantly fewer Thy-1+ T cells and a lesser capacity to generate cytotoxic T lymphocytes than did the conventionally bred nu/nu mice. Nonetheless, such cells were clearly present. IL-2 may act to cause these post-thymic T cells to proliferate. Therefore, it seems inappropriate to consider IL-2 as an inducer of the differentiation of T cells in the absence of thymic influence on the basis of the capacity of IL-2 to induce the appearance of a T-lymphocyte population in nu/nu mice.     

Interleukin-6 modulates production of T lymphocyte-derived cytokines in antigen-induced arthritis and drives inflammation-induced osteoclastogenesis

OBJECTIVE: To determine the cellular mediators of antigen-induced arthritis (AIA) and the relative contribution of members of the interleukin-6 (IL-6) family and tumor necrosis factor (TNF) in AIA. METHODS: AIA was induced in mice deficient in T and B lymphocytes, IL-6 (IL-6(-/-)), TNF (TNF(-/-)), IL-11 receptor, and oncostatin M receptor, by immunization with methylated bovine serum albumin (mBSA) followed 7 days later by intraarticular injection of mBSA. Arthritis severity was assessed histologically, and T lymphocyte responses were assessed in vitro. Anti-TNF neutralizing antibody was administered to wild-type mice during AIA. Bone marrow osteoclasts were generated in vitro via culture with RANKL and macrophage colony-stimulating factor. RESULTS: AIA was dependent on CD4+ T lymphocytes, but not CD8+ T lymphocytes or B cells. IL-6(-/-) mice had reduced AIA severity and fewer osteoclasts at sites of bone erosion. This protective effect was not seen with a deficiency of other IL-6 family members and was similar to that in TNF(-/-) mice or wild-type mice receiving TNF blockade treatment. IL-6(-/-) CD4+ T lymphocytes from draining lymph nodes had reduced antigen-induced proliferation and produced less IL-17 and less RANKL, relative to osteoprotegerin, than cells from wild-type mice. Bone marrow from IL-6(-/-) mice generated fewer osteoclasts in vitro than bone marrow from either wild-type or TNF(-/-) mice. CONCLUSION: AIA is driven by CD4+ T lymphocytes. IL-6 is an important mediator of bone destruction in AIA because it regulates T lymphocyte production of key osteoclastogenic cytokines and inflammation-induced bone marrow osteoclast differentiation. These findings have implications for reducing bone and joint damage in rheumatoid arthritis.     

Identification of a 24-kDa cytokine that is required for development of cytolytic T lymphocytes.

It is known that the production of cytolytic T lymphocytes requires growth factors such as interleukins 2 and 4 (IL-2 and IL-4). Elsewhere we have described bioassays that detect a cytokine that operates in concert with growth factor to generate cytolytic T lymphocytes. The factor that is termed cytolytic T-lymphocyte differentiation factor (CDF), together with IL-2 and lectin, mediates the formation of CD8+ killer cells in 2 days from thymocyte or peripheral lymphoid precursors. CDF is not mimicked by natural or recombinant sources of interferons, colony-stimulating factors, and IL-1 to IL-4. Here we use these bioassays to isolate and further characterize a single 24-kDa CDF protein from the conditioned medium of stimulated human blood mononuclear cells. CDF is first enriched by three successive chromatographic procedures that utilize anion exchange, hydroxyapatite, and phenyl-Superose. A single 24-kDa band with CDF activity is then isolated on 12% NaDodSO4/PAGE and clearly distinguished from the 17-kDa band of IL-2. The apparent molecular mass is similar under reducing and nonreducing conditions. After elution from NaDodSO4/PAGE the cytokine is maximally active at 0.25 nM in the CDF assay and has no growth factor activity for T lymphoblasts. To generate cytolytic CD8+, CD4- cells from spleen and lymph node T lymphocytes, IL-2 and small numbers of accessory dendritic cells must be applied together with CDF.     

PAR-2 deficient CD4+ T cells exhibit downregulation of IL-4 and upregulation of IFN-gamma after antigen challenge in mice.

BACKGROUND: To investigate the functional role of protease activated receptor (PAR) -2 in T lymphocytes, we analyzed TCR-mediated inflammatory cytokine production using PAR-2 deficient (KO) and wild type (WT) mice. METHODS: Production of serum IgE and cytokines by spleen CD4+ T cells was determined in OVA-sensitized and OVA-challenged mice of PAR-2 KO in contrast to WT mice. Phosphorylation of JNK1 and 2 was determined by Western blotting. RESULTS: A reduction in serum levels of IgE and IL-4 production by splenic CD4+ T cells from OVA-sensitized and OVA-challenged KO mice compared to WT mice was observed. By contrast, IFN-gamma production was upregulated after antigen stimulation in KO mice. Anti-CD3-mediated phosphorylation of JNK1 was upregulated in splenic CD4+ T cells from KO mice compared to WT mice. CONCLUSIONS: PAR-2 participates in the regulation of T cell cytokine production that may be caused by modulation of JNK1 phosphorylation.     

T lymphocytes downregulate granulocyte-macrophage colony-stimulating factor secretion from stimulated monocytes by increasing the secretion of monocyte-derived interleukin-10

In previous studies we characterized the cytokine regulation of granulocyte-macrophage colony-stimulating factor (GM-CSF) and granulocyte colony-stimulating factor (G-CSF) secretion by endothelial cells and monocytes and found differences in secretion pattern within and between these cell systems. In this study, the regulatory effect of T lymphocytes on CSF secretion was examined. T lymphocytes had no effect on CSF secretion by endothelial cells. In contrast, the addition of T lymphocytes significantly and dose dependently downregulated GM-CSF, but not G-CSF, secretion by monocytes. In one of our previous studies it was shown that interleukin-4 (IL-4) and interleukin-10 (IL-10) were the most potent inhibitory cytokines of CSF secretion by monocytes. Both these cytokines are produced by T lymphocytes. However, the downregulating effect on monocyte GM-CSF secretion was not due to increased secretion of T-lymphocyte-derived IL-4 or IL-10. Instead, the presence of T lymphocytes increased the secretion of monocyte-derived IL-10. It was shown earlier than IL-10 regulates CSF secretion by monocytes in an autocrine manner. Our data indicate that T lymphocytes might interfere with this autocrine regulation and thereby influence monocyte function in immune response and cell proliferation.     

Regulation of mucosal immune responses by recombinant interleukin 10 produced by intestinal epithelial cells in mice

BACKGROUND & AIMS: Interleukin (IL)-10 is a cytokine with anti-inflammatory properties. The aim of this study was to explore the effect of a site-specific delivery of IL-10 on intestinal immune responses. METHODS: Transgenic mice were created in which IL-10 is expressed by the intestinal epithelial cells. RESULTS: Transgenic mice showed a marked increase in the number of intraepithelial lymphocytes in the small intestine. Mucosal lymphocytes of transgenic animals produced fewer T helper type 1 cytokines than wild-type lymphocytes. By contrast, the production of transforming growth factor beta was increased. Moreover, the epithelial layer in transgenic mice was significantly enriched for CD4(+)CD25(+) T cells. Furthermore, transgenic mice had increased numbers of immunoglobulin A-producing B cells in the small intestine. These effects were local because splenic lymphocytes were not affected. Studies in models of inflammatory bowel disease showed that transgenic IL-10 was able to attenuate the acute colitis induced by dextran sodium sulfate administration or by adoptive transfer of CD4(+)CD45RB(high) splenocytes, with a modest effect on the chronic intestinal inflammation arising spontaneously in IL-10(-/-) mice. CONCLUSIONS: These observations provide evidence for an in vivo lymphoepithelial cross talk, by which cytokines locally produced by epithelial cells can regulate immune responses in the intestine without systemic modifications.     

Transgenic overexpression of human IL-17E results in eosinophilia,B-lymphocyte hyperplasia,and altered antibody production

We have identified and cloned a novel human cytokine with homology to cytokines of the interleukin-17 (IL-17) family, which we have termed human IL-17E (hIL-17E). With the identification of several IL-17 family members, it is critical to understand the in vivo function of these molecules. We have generated transgenic mice overexpressing hIL-17E using an apolipoprotein E (ApoE) hepatic promoter. These mice displayed changes in the peripheral blood, particularly, a 3-fold increase in total leukocytes consisting of increases in eosinophils, lymphocytes, and neutrophils. Splenomegaly and lymphoadenopathy were predominant and included marked eosinophil infiltrates and lymphoid hyperplasia. CCR3(+) eosinophils increased in the blood and lymph nodes of the transgenic mice by 50- and 300-fold, respectively. Eosinophils also increased 8- to 18-fold in the bone marrow and spleen, respectively. In the bone marrow, most of the eosinophils had an immature appearance. CD19(+) B cells increased 2- to 5-fold in the peripheral blood, 2-fold in the spleen, and 10-fold in the lymph nodes of transgenic mice, whereas CD4(+) T lymphocytes increased 2-fold in both blood and spleen. High serum levels of the cytokines IL-2, IL-4, IL-5, granulocyte colony-stimulating factor, eotaxin, and interferon gamma were observed. Consistent with B-lymphocyte increases, serum immunoglobulin (Ig) M, IgG, and IgE were significantly elevated. Antigenic challenge of the transgenic mice with keyhole limpet hemocyanin (KLH) resulted in a decrease in anti-KLH IgG accompanied by increases of anti-KLH IgA and IgE. In situ hybridization of transgenic tissues revealed that IL-17Rh1 (IL-17BR/Evi27), a receptor that binds IL-17E, is up-regulated. Taken together, these data indicate that IL-17E regulates hematopoietic and immune functions, stimulating the development of eosinophils and B lymphocytes. The fact that hIL-17E overexpression results in high levels of circulating eosinophils, IL-4, IL-5, eotaxin, and IgE suggests that IL-17E may be a proinflammatory cytokine favoring Th2-type immune responses.     

Age-related alteration of cytokine production profile by T cell subsets in mice: a flow cytometric study.

Spleen cells from young and old C57BL/6 mice were stimulated with a combination of anti-CD3 and anti-CD28 antibodies, and the profile of cytokine production was examined by two different methods; the concentrations of cytokines as measured by ELISA, and identification of cytokine-positive cells by flow cytometry. The ELISA method revealed that IL-2 production by spleen cells after stimulation was significantly lower in the old mice compared to the young mice. while IFN-gamma production was the reverse. The flow cytometric analysis showed that the percentage of IL-2 positive cells in spleen cells after the stimulation was significantly lower in the older mice than in the young mice, and vice versa for the percentage of IFN-gamma-positive cells. Regarding the T cell subsets, CD4+ T cells were a major source of IL-2 in both the young and old mice. IL-2-positive cells in both CD4+ and CD8+ T cells showed a significant decrease with age. On the contrary, CDX T cells were the major source of IFN-gamma. An age-related increase of IFN-gamma positive cells was observed in both CD4+ and CD8+ T cells. CD4 T cells were the major source of IL-4, and the percentage of IL-4-positive CD4+ T cells also increased with age, although the level of IL-4 production was modest in C57BL/6 mice compared with IL-2 and IFN-gamma. Such age-related changes of cytokine production are presumed to play an important role in the alteration of immunological capacity with age.     

Pretreatment of donor mice with granulocyte colony-stimulating factor polarizes donor T lymphocytes toward type-2 cytokine production and reduces severity of experimental graft-versus-host disease

The incidence and severity of acute graft-versus-host disease (GVHD) after allogeneic transplantation using peripheral blood progenitor cells mobilized by granulocyte colony-stimulating factor (G-CSF) appear to be no worse than those after bone marrow transplantation, despite the presence of large numbers of T cells in the donor infusion. Experimental studies have shown that type-1 T cells (secreting interleukin-2 [IL-2] and interferon-gamma) mediate acute GVHD, whereas type-2 T cells (secreting IL-4 and IL-10) can prevent acute GVHD. We tested the hypothesis that G-CSF modulates T-cell function toward a type-2 response and thus reduces the severity of acute GVHD. B6 mice were injected with G-CSF or diluent for 4 days, and their splenic T cells were stimulated in vitro with alloantigen or mitogen in the absence of G-CSF. T cells from G-CSF-treated mice showed a significant increase in IL-4 production, with a simultaneous decrease in IL-2 and interferon-gamma production in response to both stimuli. We also examined the effect of G-CSF pretreatment of donors in a GVHD model (B6- ->B6D2F1). Survival was significantly improved in recipients of G-CSF- treated donors. Concanavalin-A-induced cytokine production at day 13 after transplantation also showed an increase in IL-4 along with a decrease in IL-2 and IFN-gamma production by splenocytes from recipients of G-CSF-treated bone marrow and T cells. These data show that pretreatment of donors with G-CSF polarizes donor T cells toward the production of type-2 cytokines, which is associated with reduced type-1 cytokine production and reduced severity of acute GVHD.     

Altered hepatic lymphocyte subpopulations in obesity-related murine fatty livers: potential mechanism for sensitization to liver damage

Although obesity-related fatty livers are vulnerable to damage from endotoxin, the mechanisms involved remain obscure. The purpose of this study was to determine if immunologic priming might be involved by determining if fatty livers resemble normal livers that have been sensitized to endotoxin damage by Propionibacterium acnes infection. The latter induces interleukin (IL)-12 and -18, causing a selective reduction of CD4+NK T cells, diminished IL-4 production, deficient production of T-helper type 2 (Th-2) cytokines (e.g., IL-10), and excessive production of Th-1 cytokines (e.g., interferon gamma [IFN-gamma]). Liver and spleen lymphocyte populations and hepatic cytokine production were compared in genetically obese, ob/ob mice (a model for obesity-related fatty liver) and lean mice. Obese mice have a selective reduction of hepatic CD4+NK T cells. Serum IL-18 is also increased basally, and the hepatic mRNA levels of IL-18 and -12 are greater after endotoxin challenge. Thus, up-regulation of IL-18 and IL-12 in fatty livers may reduce hepatic CD4+NK T cells. In addition, mononuclear cells from fatty livers have decreased expression of the adhesion molecule, leukocyte factor antigen-1 (LFA-1), which is necessary for the hepatic accumulation of CD4+NK T cells. Consistent with reduced numbers of hepatic CD4+NK T cells, mononuclear cells from fatty livers produce less IL-4. Furthermore, after endotoxin treatment, hepatic induction of IL-10 is inhibited, while that of IFN-gamma is enhanced. Thus, fatty livers have inherent immunologic alterations that may predispose them to damage from endotoxin and other insults that induce a proinflammatory cytokine response.     

Retroviral gene transfer induced constitutive expression of interleukin-2 or interferon-gamma in irradiated human melanoma cells.

Cytokines are important modulators of host antitumor responses. Two of these cytokines, interleukin-2 (IL-2) and interferon gamma (IFN-gamma), are produced after antigen-induced activation of helper lymphocytes. The cytokines are released into the immediate vicinity where they either interact with the appropriate receptors on effector cell populations or are rapidly degraded. To mimic this physiologic release of cytokines at the effector-target site, we used retroviral vectors to transduce melanoma cells with the IL-2 or IFN-gamma cDNA. Five melanoma cell lines were transduced with IL-2- or IFN-gamma-containing vectors and secreted IL-2 at 1 to 40 U/mL/10(6) cells/24 h or IFN-gamma 1 to 8 U/mL/10(6) cells/24 h, respectively. After gamma irradiation, these cells continued to secrete cytokines for about 3 to 4 weeks. Secretion of IFN-gamma induced upregulation of major histocompatibility complex class I molecules in a subset of melanoma cell lines. IL-2 production by human melanoma xenografts induced tumor rejection in BALB/c nu/nu mice, showing the in vivo effect of this cytokine. This study shows that (1) human melanoma cells can be stably transduced with cytokine-containing retroviral vectors; (2) cytokines are secreted constitutively by the transduced tumor cells and have the expected biologic effects in vitro and in vivo; and (3) after gamma irradiation, cytokines continue to be secreted for several weeks. These data suggest that irradiated cytokine-secreting allogenic or autologous tumor cells can be used in vaccination protocols for cancer patients.     

IL-6 blockade preferentially inhibits Th17 differentiation in collagen-induced arthritis

We examined the time course of cytokine production by CD4 T cells from mice with collagen-induced arthritis (CIA), and we determined the influence of interleukin-6 (IL-6) blockade on cytokine production. CD4 T cells purified from spleen were cultured with both collagen and anti-CD28 antibody for 48 h and the production of interferon-γ (IFN-γ), IL-4, and IL-17 by the cells, secreted into the supernatants, was measured at various time intervals. The production of all these cytokines started 7 days after the first immunization. A marked increase in IFN-γ production was observed after the second immunization, but IL-4 and IL-17 production was not affected by a second immunization. A single injection of anti-mouse IL-6 receptor antibody (MR16-1) on the day of the first immunization suppressed the onset of arthritis. IL-17 production by CD4 T cells from MR16-1-treated mice was significantly lower than that from the control mice. On the other hand, treatment with MR16-1 showed only a tendency to suppress the production of IL-4 and IFN-γ. Injection of MR16-1 on day 21 did not suppress the onset of arthritis. We examined the direct influence of MR16-1 on cytokine production by differentiated CD4 T cells from arthritic mice. Production of IL-4, IFN-γ, and IL-17 was not affected by MR16-1. In conclusion, IL-6 inhibition preferentially suppresses the induction of Th17 cells and does not seem to impact on cytokine production of already differentiated Th17 cells.     

GM-CSF promotes differentiation of human dendritic cells and T lymphocytes toward a predominantly type 1 proinflammatory response

OBJECTIVE: We recently demonstrated that patients with high levels of circulating dendritic cells (DC) and interleukin (IL)-12 are associated with reduced cancer relapse after hematopoietic stem cell transplantation. Identifying a growth factor that can promote these immune functions may have beneficial anti-tumor effects. We investigated the hypothesis that granulocyte-macrophage colony-stimulating factor (GM-CSF) induces IL-12 production and polarizes T lymphocytes toward a proinflammatory response. MATERIALS AND METHODS: Peripheral blood mononuclear cells (PBMC), T lymphocytes, and antigen-presenting cells (APC) were cultured with GM-CSF and compared with no growth factors (control), G-CSF, or both GM-CSF and G-CSF. Cells were matured with either lipopolysaccharide or lectin (phytohemagglutinin). Type 1 and type 2 cytokines were measured by enzyme-linked immunosorbent assay. Induction of allogeneic T-lymphocyte proliferation induced by GM-CSF-stimulated APC was measured by mixed lymphocyte reaction. DC were measured by flow cytometry. RESULTS: Levels of type 1 (IL-12, interferon-gamma, tumor necrosis factor-alpha) cytokines increased while type 2 (IL-10 and IL-4) cytokines decreased after stimulation of PBMC, T lymphocytes, and APC with GM-CSF. APC treated with GM-CSF induced higher proliferation of allogeneic T cells. CD11c and CD123-positive DC proliferated after exposure to GM-CSF. Both subtypes of DC (DC1 and DC2) were increased by GM-CSF. CONCLUSIONS: GM-CSF induces production of type 1 proinflammatory cytokines by human PBMC, T lymphocytes, and APC. Type 2 cytokines are downregulated by GM-CSF and proliferation of allogeneic T cells is increased. These results demonstrate the potential for GM-CSF as a clinical agent for immune stimulation.     

Trypanosoma brucei infection in nude mice: B lymphocyte function is suppressed in the absence of T lymphocytes

B lymphocyte function was assessed in outbred nude mice and nu/+controls infected with Trypanosoma brucei brucei. On day 10 of the infection in outbred nu/nu mice in which the initial wave of parasites was strongly controlled, B cell function was unaltered on enhanced compared with uninfected animals or infected nu/+. In other nu/nu mice unable to control the initial parasitaemia, thymidine incorporation and Ig secretion by spleen cells were increased on day 10 and their response to lipopolysaccharide in vitro negated. By day 15 however, even the spleen cells of infected nu/nu which controlled the initial wave of parasites were proliferating and secreting Ig on removal from the mice and they were unable to respond to LPS in vitro. These experiments confirm results of a previous study of B cell function in T cell-depleted mice (Askonas et al. 1979). T. b. brucei infection of mice causes both enhanced Ig production and suppression of the ability of B cells to respond to mitogen even in the absence of T cells, but the presence of T cells may accelerate the changes which occur in B lymphocytes following this infection.     

Activation-induced cell death of peripheral blood T lymphocytes in patients with primary Sjögren’s syndrome

Activation-induced cell death (AICD) in T lymphocytes is important for the maintenance of peripheral tolerance. We studied AICD of peripheral blood T cells from patients with primary Sjögren’s syndrome (SS). AICD was induced in mitogen-activated T cellsin vitro using mAb to CD3 or Fas (CD95). Cell death and proliferation, Fas and Fas ligand (FasL) expression, and soluble Fas and soluble FasL production were measured. Surface phenotypes and cytokine production of AICD-surviving cells and effects of cytokines on AICD were examined. Anti-CD3 mAb induced cell death is SS and normal T cells in the presence of exogenous interleukin (IL)-2. In the absence of IL-2 anti-CD3 mAb induced cell proliferation in SS and normal T cells. There was no significant difference in Fas/FasL expression and sFas/sFasL production between SS patients and normals. AICD-surviving cells consisted of more CD4⁺ T cells and less CD8⁺ T cells in SS compared to normals. AICD-surviving cells produced abundant interferon-γ and little IL-4. There was no significant difference in the effects of cytokines on AICD between SS patients and normals. These findings suggest that IL-2 is a critical factor for AICD. AICD works almost normally in SS T cells when sufficient IL-2 is present prior to T cell receptor re-stimulation.