Augmentation of effector CD8+ T cell generation with enhanced granzyme B expression by IL-27

IL-27 is a novel IL-12 family member that plays a role in the early regulation of Th1 initiation. We have recently demonstrated that IL-27 has a potent antitumor activity, which is mainly mediated through CD8+ T cells, and also has an adjuvant activity to induce epitope-specific CTL in vivo. In this study, we further investigated the in vitro effect of IL-27 on CD8+ T cells of mouse spleen cells. In a manner similar to CD4+ T cells, IL-27 activated STAT1, -2, -3, -4, and -5, and augmented the expression of T-bet, IL-12Rbeta2, and granzyme B, and slightly that of perforin in naive CD8+ T cells stimulated with anti-CD3. IL-27 induced synergistic IFN-gamma production with IL-12 and proliferation of naive CD8+ T cells. Moreover, IL-27 enhanced proliferation of CD4+ T cell-depleted spleen cells stimulated by allogeneic spleen cells and augmented the generation of CTL. In STAT1-deficient naive CD8+ T cells, IL-27-induced proliferation was not reduced, but synergistic IFN-gamma production with IL-12 was diminished with decreased expression of T-bet, IL-12Rbeta2, granzyme B, and perforin. In T-bet-deficient naive CD8+ T cells, IL-27-induced proliferation was hardly reduced, but synergistic IFN-gamma production with IL-12 was diminished with decreased expression of IL-12Rbeta2, granzyme B, and perforin. However, IL-27 still augmented the generation of CTL from T-bet-deficient CD4+ T cell-depleted spleen cells stimulated by allogeneic spleen cells with increased granzyme B expression. These results suggest that IL-27 directly acts on naive CD8+ T cells in T-bet-dependent and -independent manners and augments generation of CTL with enhanced granzyme B expression.     

IL-27 induces the production of IgG1 by human B cells

It has been reported that IL-27 specifically induces the production of IgG2a by mouse B cells and inhibits IL-4-induced IgG1 synthesis. Here, we show that human na?ve cord blood expresses a functional IL-27 receptor, consisting of the TCCR and gp130 subunits, although at lower levels as compared to na?ve and memory splenic B cells. IL-27 does not induce proliferative responses and does not increase IgG1 production by CD19(+)CD27(+) memory B cells. However, it induces a low, but significant production of IgG1 by na?ve CD19(+)CD27(-)IgD(+)IgG(-) spleen and cord blood B cells, activated via CD40, whereas it has no effect on the production of the other IgG subclasses. In addition, IL-27 induces the differentiation of a population of B cells that express high levels of CD38, in association with a down-regulation of surface IgD expression, and that are surface IgG(+/int), CD20(low), CD27(high), indicating that IL-27 promotes isotype switching and plasma cell differentiation of naive B cells. However, as compared to the effects of IL-21 and IL-10, both switch factors for human IgG1 and IgG3, those of IL-27 are modest and regulate exclusively the production of IgG1. Finally, although IL-27 has no effect on IL-4 and anti-CD40-induced Cepsilon germline promoter activity, it up-regulates IL-4-induced IgE production by naive B cells. These results point to a partial redundancy of switch factors regulating the production of IgG1 in humans, and furthermore indicate the existence of a common regulation of the human IgG1and murine IgG2a isotypes by IL-27.     

TSC1/2 signaling complex is essential for peripheral naïve CD8+ T cell survival and homeostasis in mice

The PI3K-Akt-mTOR pathway plays crucial roles in regulating both innate and adaptive immunity. However, the role of TSC1, a critical negative regulator of mTOR, in peripheral T cell homeostasis remains elusive. With T cell-specific Tsc1 conditional knockout (Tsc1 KO) mice, we found that peripheral na?ve CD8(+) T cells but not CD4(+) T cells were severely reduced. Tsc1 KO na?ve CD8(+) T cells showed profound survival defect in an adoptive transfer model and in culture with either stimulation of IL-7 or IL-15, despite comparable CD122 and CD127 expression between control and KO CD8(+) T cells. IL-7 stimulated phosphorylation of Akt(S473) was diminished in Tsc1 KO na?ve CD8(+)T cells due to hyperactive mTOR-mediated feedback suppression on PI3K-AKT signaling. Furthermore, impaired Foxo1/Foxo3a phosphorylation and increased pro-apoptotic Bim expression in Tsc1 KO na?ve CD8(+)T cells were observed upon stimulation of IL-7. Collectively, our study suggests that TSC1 plays an essential role in regulating peripheral na?ve CD8(+) T cell homeostasis, possible via an mTOR-Akt-FoxO-Bim signaling pathway.     

Regulation of CD28 expression on umbilical cord blood and adult peripheral blood CD8+ T cells by interleukin(IL)-15/IL-21

Interleukin (IL)-15 and IL-21, both belonging to common γ-chain-signaling cytokine family, have an important role to maintain homeostatic proliferation of CD8(+) T cells. CD28, an essential co-stimulatory molecule on T cells, may be a marker of replicative senescence. We investigated the effect of IL-15 and IL-21, alone or in combination, on activation, apoptosis, cytokine production and cytotoxic function of magnetic bead purified umbilical cord blood (UCB) and adult peripheral blood (APB) CD8(+) T cells with regards to their CD28 expression. We established that (1) IL-15-induced CD8(+) T cell proliferation was associated with a preferential expansion of CD28(-) population in UCB, which could be partially counteracted by IL-21; (2) UCB CD8(+) T cells were more readily responsive to IL-15 compared to their adult counterparts in terms of CD69 expression, with the majority of CD69-bearing CD8(+) T cells were CD28(-); (3) IL-21 further promoted interferon-gamma, but not tumor necrosis factor-alpha production from IL-15 treated CD8(+) T cells; (4) IL-21 also synergized with IL-15 to enhance perforin and granzyme B expression of CD8(+) T cells, especially in APB CD8(+)CD28(-) subsets; (5) IL-21 resulted in CD8(+) T cells apoptosis both in APB and UCB cells, mainly in CD8(+)CD28(-) subsets. Taken together, we demonstrate differential IL-15/IL-21 response in UCB CD8(+) T cells with regards to CD28 expression. Our results suggest that combining IL-21 and IL-15 immunotherapy may be better than IL-15 alone to ameliorate graft-versus-host disease while preserving antitumor effect in the post-UCB transplantation period.     

Profound enhancement of the IL-12/IL-18 pathway of IFN-gamma secretion in human CD8+ memory T cell subsets via IL-15

Human memory CD8(+) T cell subsets, termed central memory and effector memory T cells, can be identified by expression of CD45RA, CD62 ligand (CD62L), and CCR7. Accordingly, functional differences have been described for each subset, reflecting unique roles in immunological memory. The common gamma-chain cytokines IL-15 and IL-7 have been shown to induce proliferation and differentiation of human CD8(+) T cell subsets, as well as increased effector functions (i.e., cytokines, cytotoxicity). In this study, we observed that addition of IL-15 or IL-7 to cultures of human CD8(+) T cells profoundly enhanced the IL-12-IL-18 pathway of IFN-gamma production. Importantly, IL-15 and IL-7 lowered the threshold concentrations of IL-12 and IL-18 required for induction of IFN-gamma by 100-fold. Comparison of IL-15 and IL-7 demonstrated that IL-15 was superior in its ability to enhance IL-12-IL-18-induced IFN-gamma, without evidence of a synergistic effect between IL-15 and IL-7. We also observed that IL-15- and IL-7-mediated enhancement of IL-12-IL-18-induced IFN-gamma production was a functional property of effector memory CD8(+) T cells. Despite a lack of association between cell division and acquisition of IL-12-IL-18-induced IFN-gamma, down-regulation of CD62L expression correlated well with increased IL-12-IL-18-induced IFN-gamma. Purified central memory T cells stimulated with IL-15 and IL-7 down-regulated CD62L and acquired potent IL-12-IL-18-induced IFN-gamma similar to effector memory T cells. Thus, in addition to its known role in development of T cell memory, IL-15 may amplify memory CD8(+) T cell effector functions by increasing sensitivity to proinflammatory cytokine stimulation.     

Induction of IgG2a class switching in B cells by IL-27

IL-27 is a novel IL-12 family member that plays a role in the early regulation of Th1 initiation. However, its role in B cells remains unexplored. We here show a role for IL-27 in the induction of T-bet expression and regulation of Ig class switching in B cells. Expression of WSX-1, one subunit of IL-27R, was detected at the mRNA level in primary mouse spleen B cells, and stimulation of these B cells by IL-27 rapidly activated STAT1. IL-27 then induced T-bet expression and IgG2a, but not IgG1, class switching in B cells activated with anti-CD40 or LPS. In contrast, IL-27 inhibited IgG1 class switching induced by IL-4 in activated B cells. Similar induction of STAT1 activation, T-bet expression and IgG2a class switching was observed in IFN-gamma-deficient B cells, but not in STAT1-deficient ones. The induction of IgG2a class switching was abolished in T-bet-deficient B cells activated with LPS. These results suggest that primary spleen B cells express functional IL-27R and that the stimulation of these B cells by IL-27 induces T-bet expression and IgG2a, but not IgG1, class switching in a STAT1-dependent but IFN-gamma-independent manner. The IL-27-induced IgG2a class switching is highly dependent on T-bet in response to T-independent stimuli such as LPS. Thus, IL-27 may be a novel attractive candidate as a therapeutic agent against diseases such as allergic disorders by not only regulating Th1 differentiation but also directly acting on B cells and inducing IgG2a class switching.     

Human B cells differentiate into granzyme B-secreting cytotoxic B lymphocytes upon incomplete T-cell help

Recently, CD4(+) T helper cells were shown to induce differentiation of human B cells into plasma cells by expressing interleukin (IL-)21 and CD40 ligand (CD40L). In the present study we show, that in the absence of CD40L, CD4(+) T cell-derived IL-21 induces differentiation of B cells into granzyme B (GzmB)-secreting cytotoxic cells. Using fluorescence-activated cell sorting (FACS) analysis, ELISpot and confocal microscopy, we demonstrate that CD4(+) T cells, activated via their T-cell receptor without co-stimulation, can produce IL-21, but do not express CD40L and rapidly induce GzmB in co-cultured B cells in an IL-21 receptor-dependent manner. Of note, we confirmed these results with recombinant reagents, highlighting that CD40L suppresses IL-21-induced GzmB induction in B cells in a dose-dependent manner. Surprisingly, although GzmB-secreting B cells did not express perforin, they were able to transfer active GzmB to tumor cell lines, thereby effectively inducing apoptosis. In contrast, no cytotoxic effects were found when effector B cells were activated with IL-2 instead of IL-21 or when target cells were cultured with IL-21 alone. Our findings suggest GzmB(+) cytotoxic B cells may have a role in early cellular immune responses including tumor immunosurveillance, before fully activated, antigen-specific cytotoxic T cells are on the spot. CD40 ligand determines whether IL-21 induces differentiation of B cells into plasma cells or into granzyme B-secreting cytotoxic cells.     

Functional characterization of a nonmammalian IL-21: rainbow trout Oncorhynchus mykiss IL-21 upregulates the expression of the Th cell signature cytokines IFN-gamma, IL-10, and IL-22

In mammals, IL-21 is a common γ chain cytokine produced by activated CD4(+) T cells and NKT cells that acts on multiple lineages of cells. Although IL-21 has also been discovered in birds, amphibians, and fish, to date, no functional studies have been reported for any nonmammalian IL-21 molecule. We have sequenced an IL-21 gene (tIL-21) in rainbow trout, which has a six-exon/five-intron structure, is expressed in immune tissues, and is induced by bacterial and viral infection and the T cell stimulant PHA. In contrast to mammals, calcium ionophore and PMA act synergistically to induce tIL-21. Recombinant tIL-21 (rtIL-21) induced a rapid and long-lasting (4-72 h) induction of expression of IFN-γ, IL-10, and IL-22, signature cytokines for Th1-, Th2-, and Th17-type responses, respectively, in head kidney leukocytes. However, rtIL-21 had little effects on the expression of other cytokines studied. rtIL-21 maintained the expression of CD8α, CD8β, and IgM at a late stage of stimulation when their expression was significantly decreased in controls and increased the expression of the Th cell markers CD4, T-bet, and GATA3. Intraperitoneal injection of rtIL-21 confirmed the in vitro bioactivity and increased the expression of IFN-γ, IL-10, IL-21, IL-22, CD8, and IgM. Inhibition experiments revealed that the activation of JAK/STAT3, Akt1/2, and PI3K pathways were responsible for rtIL-21 action. This study helps to clarify the role of IL-21 in lower vertebrates for the first time, to our knowledge, and suggests IL-21 is a likely key regulator of T and B cell function in fish.     

Regulation of immune function by calorie restriction and cyclophosphamide treatment in lupus-prone NZB/NZW F1 mice

We compared the effects of calorie restriction (CR) and cyclophosphamide (CTX) on the progression of lupus nephritis and immunological changes in NZB/NZW F1 mice. Ad libitum (AL)/CTX and CR delayed onset of proteinuria and significantly decreased serum levels of anti-dsDNA, anti-histone, and circulating immune complex antibodies. CTX and CR prevented the increase in and activation of B cells, the decline in CD8(+) T cells, and maintained a higher proportion of na?ve CD4(+) and CD8(+) cells. MHC class I antigen and LFA-1 expression on CD8(+) T cells and MHC class II antigen on B cells were also decreased. AL/CTX and CR prevented the increase in production of IL-10 and up-regulated IL-2 production in T cells ex vivo. We concluded that both CR and CTX can delay the onset of autoimmune disease, in part by maintaining higher numbers of na?ve T cells and the immune responsiveness of T cells and decreasing the proportion of B cells.     

Tacrolimus potently inhibits human osteoclastogenesis induced by IL-17 from human monocytes alone and suppresses human Th17 differentiation

Tacrolimus (FK506, Prograf?) is an orally available, T cell specific and anti-inflammatory agent that has been proposed as a therapeutic drug in rheumatoid arthritis (RA) patients. It has been known that T cells have a critical role in the pathogenesis of RA. Recent studies suggest that Th17 cells, which mainly produce IL-17, are involved in many autoimmune inflammatory disease including RA. The present study was undertaken to assess the effect of tacrolimus on IL-17-induced human osteoclastogenesis and human Th17 differentiation. Human CD14(+) monocytes were cultured in the presence of macrophage-colony stimulating factor (M-CSF) and IL-17. From day 4, tacrolimus was added to these cultures. Osteoclasts were immunohistologically stained for vitronectin receptor 10days later. IL-17 production from activated T cells stimulated with IL-23 was measured by enzyme-linked immunosorbent assay (ELISA). Th17 differentiation from na?ve T cells was assayed by flow cytometry. Tacrolimus potently inhibited IL-17-induced osteoclastogenesis from human monocytes and osteoclast activation. Addition of tacrolimus also reduced production of IL-17 in human activated T cells stimulated with IL-23. Interestingly, the population of human IL-17(+)IFN-γ(-) CD4 T cells or IL-17(+)TNF-α(+) CD4 T cells were decreased by adding of tacrolimus. The present study demonstrates that the inhibitory effect of tacrolimus on IL-17-induced osteoclastogenesis from human monocytes. Tacrolimus also inhibited expression of IL-17 or TNF-α by reducing the proportion of Th17, suggesting that therapeutic effect on Th17-associated disease such as RA, inflammatory bowel disease, multiple sclerosis, psoriasis, or allograft rejection.     

An indispensable role for STAT1 in IL-27-induced T-bet expression but not proliferation of naive CD4+ T cells

IL-27 is a novel IL-12 family member that plays a role in the early regulation of Th1 initiation, induces proliferation of naive CD4+ T cells, and synergizes with IL-12 in IFN-gamma production. It has been recently reported that IL-27 induces T-bet and IL-12Rbeta2 expression through JAK1/STAT1 activation. In the present study, we further investigated the JAK/STAT signaling molecules activated by IL-27 and also the role of STAT1 in IL-27-mediated responses using STAT1-deficient mice. In addition to JAK1 and STAT1, IL-27-activated JAK2, tyrosine kinase-2, and STAT2, -3, and -5 in naive CD4+ T cells. The activation of STAT2 and STAT5, but not of STAT3, was greatly diminished in STAT1-deficient naive CD4+ T cells. Comparable proliferative response to IL-27 was observed between STAT1-deficient and wild-type naive CD4+ T cells. In contrast, IL-27 hardly induced T-bet and subsequent IL-12Rbeta2 expression, and synergistic IFN-gamma production by IL-27 and IL-12 was impaired in STAT1-deficient naive CD4+ T cells. Moreover, IL-27 augmented the expression of MHC class I on naive CD4+ T cells in a STAT1-dependent manner. These results suggest that IL-27 activates JAK1 and -2, tyrosine kinase-2, STAT1, -2, -3, and -5 in naive CD4+ T cells and that STAT1 plays an indispensable role in IL-27-induced T-bet and subsequent IL-12Rbeta2 expression and MHC class I expression as well but not proliferation, while STAT3 presumably plays an important role in IL-27-induced proliferation.     

CD27 stimulation promotes the frequency of IL-7 receptor-expressing memory precursors and prevents IL-12-mediated loss of CD8(+) T cell memory in the absence of CD4(+) T cell help

Fully functional CD8(+) T cell memory is highly dependent upon CD4(+) T cell support. CD4(+) T cells play a critical role in inducing the expression of CD70, the ligand for CD27, on dendritic cells. In this study, we demonstrate that CD27 stimulation during primary CD8(+) T cell responses regulates the ability to mount secondary CD8(+) T cell responses. CD27 stimulation during vaccinia and dendritic cell immunization controls the expression of the IL-7R (CD127), which has been shown to be necessary for memory CD8(+) T cell survival. Furthermore, CD27 stimulation during primary CD8(+) T cell responses to vaccinia virus restrained the late expression on memory precursor cells of cytokine receptors that support terminal differentiation. The formation of CD8(+) T cell memory precursors and secondary CD8(+) T cell responses was restored in the absence of CD27 costimulation when endogenous IL-12 was not available. Similarly, the lesion in CD8(+) T cell memory that occurs in the absence of CD4(+) T cells did not occur in mice lacking IL-12. These data indicate that CD4(+) T cell help and, by extension, CD27 stimulation support CD8(+) T cell memory by modulating the expression of cytokine receptors that influence the differentiation and survival of memory CD8(+) T cells.     

Signaling thresholds govern heterogeneity in IL-7-receptor-mediated responses of naïve CD8(+) T cells

Variable sensitivity to T-cell-receptor (TCR)- and IL-7-receptor (IL-7R)-mediated homeostatic signals among na?ve T cells has thus far been largely attributed to differences in TCR specificity. We show here that even when withdrawn from self-peptide-induced TCR stimulation, CD8(+) T cells exhibit heterogeneous responses to interleukin-7 (IL-7) that are mechanistically associated with IL-7R expression differences that correlate with relative CD5 expression. Whereas CD5(hi) and CD5(lo) T cells survive equivalently in the presence of saturating IL-7 levels in vitro, CD5(hi) T cells proliferate more robustly. Conversely, CD5(lo) T cells exhibit prolonged survival when withdrawn from homeostatic stimuli. Through quantitative experimental analysis of signaling downstream of IL-7R, we find that the enhanced IL-7 responsiveness of CD5(hi) T cells is directly related to their greater surface IL-7R expression. Further, we identify a quantitative threshold in IL-7R-mediated signaling capacity required for proliferation that lies well above an analogous threshold requirement for survival. These distinct thresholds allow subtle differences in IL-7R expression between CD5(lo) and CD5(hi) T cells to give rise to significant variations in their respective IL-7-induced proliferation, without altering survival. Heterogeneous IL-7 responsiveness is observed similarly in vivo, with CD5(hi) na?ve T cells proliferating preferentially in lymphopenic mice or lymphoreplete mice administered with exogenous IL-7. However, IL-7 in lymphoreplete mice appears to be maintained at an effective level for preserving homeostasis, such that neither CD5(hi) IL-7R(hi) nor CD5(lo) IL-7R(lo) T cells proliferate or survive preferentially. Our findings indicate that IL-7R-mediated signaling not only maintains the size but also impacts the diversity of the na?ve T-cell repertoire.     

Differential effects of IL-27 on human B cell subsets

IL-27 is a novel heterodimeric cytokine of the IL-12 family that plays an important role in the regulation of T cell responses. Its role on human B cells has not been previously studied. In this study, we show that both chains of the IL-27 receptor complex, IL-27R and gp130, are constitutively expressed at the surface of naive and memory human tonsillar B cells, and are induced on germinal center B cells following CD40 stimulation. In naive B cells, IL-27 induced strong STAT1 and STAT3 phosphorylation, whereas it induced moderate STAT1 and low STAT3 activation in memory B cells. IL-27 induced T-bet expression in naive and memory B cells stimulated by CD40 or surface Ig engagement, but induced significant IL-12Rbeta2 surface expression in anti-Ig-stimulated naive B cells only. In anti-Ig-stimulated naive or memory B cells, IL-27 also induced CD54, CD86, and CD95 surface expression. In addition, IL-27 increased proliferation of anti-Ig-activated naive B cells and of anti-CD40-activated naive and germinal center B cells, but not of CD40-activated memory B cells. These data indicate that the B cell response to IL-27 is modulated during B cell differentiation and varies depending on the mode of B cell activation.     

The IL-7Rα pathway is quantitatively and functionally altered in CD8 T cells in multiple sclerosis

The IL-7Rα single nucleotide polymorphism rs6897932 is associated with an increased risk for multiple sclerosis (MS). IL-7Rα is a promising candidate to be involved in autoimmunity, because it regulates T cell homeostasis, proliferation, and antiapoptotic signaling. However, the exact underlying mechanisms in the pathogenesis of MS are poorly understood. We investigated whether CD4 and CD8 lymphocyte subsets differed in IL-7Rα expression and functionality in 78 MS patients compared with 59 healthy controls (HC). A significantly higher frequency of IL-7Rα(+) CD8 effector memory (CD8EM) was found in MS. Moreover, IL-7Rα membrane expression was significantly increased in MS in naive and memory CD8 (all p < 0.05) with a similar trend in CD8EM (p = 0.055). No correlation was found between the expression level or frequency of IL-7Rα(+)CD8(+) and rs6897932 risk allele carriership. Upon IL-7 stimulation, MS patients had stronger STAT5 activation in CD8EM compared with HC. IL-7 stimulation had a differential effect on both mRNA and protein expression of granzyme A and granzyme B between MS and HC. Stainings of different lesions in postmortem MS brain material showed expression of IL-7 and CD8(+)IL-7Rα(+) in preactive, but not in active, demyelinating MS lesions, indicating involvement of IL-7Rα(+) lymphocytes in lesion development. The intralesional production of IL-7 in combination with the lower threshold for IL-7-induced cytotoxicity in MS may enhance the pathogenicity of these CD8 T cells. This is of special interest in light of the established demyelinating and cytotoxic actions of granzyme A.     

Perforin expression in human peripheral blood mononuclear cells. Definition of an IL-2-independent pathway of perforin induction in CD8+ T cells.

Perforin gene expression upon in vitro stimulation was studied at the mRNA level in normal human PBMC and in subpopulations. Freshly isolated PBMC express low levels of perforin mRNA. Increased perforin expression is rapidly induced by the calcium ionophore A23187 and by rIL-2. Phorbolesters (PMA), by comparison, are poor inducers of perforin RNA. Perforin induction by Ca-ionophore, unlike granzyme 2 and IL-2 induction, did not synergize with phorbolesters in PBMC or in purified T cells. Instead, perforin mRNA induction by A23187 in purified T cells requires the presence of adherent cells. Ca-ionophore plus adherent cell-induced perforin occurred in CD8+ T cells and was abolished by depletion of CD8+ T cells but not by depletion of CD4+ T cells. Adherent cells alone did not express perforin under any condition. Perforin mRNA induction by both A23187 and by rIL-2 is independent of de novo protein synthesis. The half-life of perforin mRNA induced by either stimulus is approximately 100 min. Cyclosporin A completely abrogates perforin induction by A23187 but only slightly inhibits the effect of rIL-2 on perforin mRNA expression. These data show that A23187 activates perforin gene expression in CD8+ cells by an IL-2-independent pathway and that the molecular mechanism of perforin expression may be different from the one induced by IL-2. Granzyme 2 (human leukocyte protease-HLP, homologous to murine granzyme B) mRNA expression was studied in comparison to perforin. Granzyme 2 in contrast to perforin responds to the synergistic action of phorbolester and Ca-ionophore in PBMC. In addition, the kinetics of the induction of granzyme and perforin mRNA, by various signals are different. Our data suggest that situations in vivo may exist that allow perforin expression in CD8+ cells in the absence of cytokines by a combination of Ca signals and accessory receptor ligation. The same signals may not be sufficient for granzyme 2 expression in any T cell subpopulation.     

Signaling events involved in interleukin 27 (IL-27)-induced proliferation of human naive CD4+ T cells and B cells

IL-27 induces stronger proliferation of naive than memory human B cells and CD4(+) T cells. In B cells, this differential response is associated with similar levels of IL-27 receptor chains, IL-27Rα and gp130, in both subsets and stronger STAT1 and STAT3 activation by IL-27 in naive B cells. Here, we show that the stronger proliferative response of CD3-stimulated naive CD4(+) T cells to IL-27 is associated with lower levels of IL-27Rα but higher levels of gp130 compared with memory CD4(+) T cells. IL-27 signaling differs between naive and memory CD4(+) T cells, as shown by more sustained STAT1, -3, and -5 activation and weaker activation of SHP-2 in naive CD4(+) T cells. In the latter, IL-27 increases G0/G1 to S phase transition, cell division and, in some cases, cell survival. IL-27 proliferative effect on naive CD4(+) T cells is independent of MAPK, but is dependent on c-Myc and Pim-1 induction by IL-27 and is associated with induction of cyclin D2, cyclin D3, and CDK4 by IL-27 in a c-Myc and Pim-1-dependent manner. In BCR-stimulated naive B cells, IL-27 only increases entry in the S phase and induces the expression of Pim-1 and of cyclins A, D2, and D3. In these cells, inhibition of Pim-1 inhibits IL-27 effect on proliferation and cyclin induction. Altogether, these data indicate that IL-27 mediates proliferation of naive CD4(+) T cells and B cells through induction of both common and distinct sets of cell cycle regulators.