Macrophages, CD4+ or CD8+ cells are each sufficient for protection against Chlamydia pneumoniae infection through their ability to secrete IFN-gamma

By using a T, B, or NK cell-deficient mouse strain (recombinase-activating gene (RAG)-1(-/-)/common cytokine receptor gamma-chain (gamma(C)R)), and T and B cell and IFN-gamma-deficient (RAG-1(-/-)/IFN-gamma(-/-)) mice, we have studied the generation of immunity against infection by Chlamydia pneumoniae. We found that IFN-gamma secreted by innate-cell populations protect against C. pneumoniae infection. However, NK cells were not needed for such IFN-gamma-dependent innate immune protection. Inoculation of wild type, but not IFN-gamma(-/-) bone marrow-derived macrophages protected RAG-1(-/-)/IFN-gamma(-/-) mice against C. pneumoniae infection. In line, pulmonary macrophages from RAG-1(-/-) C. pneumoniae-infected mice expressed IFN-gamma mRNA. Reconstitution of RAG-1(-/-)/gamma(c)R(-/-) or RAG-1(-/-)/IFN-gamma(-/-) mice with CD4(+) or CD8(+) cells by i.v. transfer of FACS sorted wild type spleen cells (SC) increased resistance to C. pneumoniae infection. On the contrary, no protection was observed upon transfer of IFN-gamma(-/-) CD4(+) or IFN-gamma(-/-) CD8(+) SC. T cell-dependent protection against C. pneumoniae was weaker when IFN-gammaR(-/-) CD4(+) or IFN-gammaR(-/-) CD8(+) SC were inoculated into RAG-1(-/-)/IFN-gamma(-/-) mice. Thus both nonlymphoid and T cell-derived IFN-gamma can play a central and complementary role in protection against C. pneumoniae. IFN-gamma secreted by nonlymphoid cells was not required for T cell-mediated protection against C. pneumoniae; however, IFN-gamma regulated T cell protective functions.     

Regulation of IFN-gamma signaling is essential for the cytotoxic activity of CD8(+) T cells.

Previous studies have demonstrated that, as naive murine CD4(+) cells differentiate into Th1 cells, they lose expression of the second chain of IFN-gammaR (IFN-gammaR2). Hence, the IFN-gamma-producing subset of Th cells is unresponsive to IFN-gamma. Analysis of IFN-gamma-producing CD8(+) T cells demonstrates that, like Th1 cells, these cells do not express IFN-gammaR2. To define the importance of IFN-gamma signaling for the development of functional CD8(+) T cells, mice either lacking IFN-gammaR2 or overexpressing this protein were examined. While CD8(+) T cell development and function appear normal in IFN-gammaR2(-/-) mice, CD8(+) T cell function in IFN-gammaR2 transgenic is altered. IFN-gammaR2 transgenic CD8(+) T cells are unable to lyse target cells in vitro. However, these cells produce Fas ligand, perforin, and granzyme B, the effector molecules required for killing. Interestingly, TG CD8(+) T cells proliferate normally and produce cytokines, such as IFN-gamma in response to antigenic stimulation. Therefore, although IFN-gamma signaling is not required for the generation of normal cytotoxic T cells, constitutive IFN-gamma signaling can selectively impair the cytotoxic function of CD8(+) T cells.     

CD11b+ monocytes abrogate Th17 CD4+ T cell-mediated experimental autoimmune myocarditis

Experimental autoimmune myocarditis (EAM) represents a Th17 T cell-mediated mouse model of postinflammatory heart disease. In BALB/c wild-type mice, EAM is a self-limiting disease, peaking 21 days after alpha-myosin H chain peptide (MyHC-alpha)/CFA immunization and largely resolving thereafter. In IFN-gammaR(-/-) mice, however, EAM is exacerbated and shows a chronic progressive disease course. We found that this progressive disease course paralleled persistently elevated IL-17 release from T cells infiltrating the hearts of IFN-gammaR(-/-) mice 30 days after immunization. In fact, IL-17 promoted the recruitment of CD11b(+) monocytes, the major heart-infiltrating cells in EAM. In turn, CD11b(+) monocytes suppressed MyHC-alpha-specific Th17 T cell responses IFN-gamma-dependently in vitro. In vivo, injection of IFN-gammaR(+/+)CD11b(+), but not IFN-gammaR(-/-)CD11b(+), monocytes, suppressed MyHC-alpha-specific T cells, and abrogated the progressive disease course in IFN-gammaR(-/-) mice. Finally, coinjection of MyHC-alpha-specific, but not OVA-transgenic, IFN-gamma-releasing CD4(+) Th1 T cell lines, together with MyHC-alpha-specific Th17 T cells protected RAG2(-/-) mice from EAM. In conclusion, CD11b(+) monocytes play a dual role in EAM: as a major cellular substrate of IL-17-induced inflammation and as mediators of an IFN-gamma-dependent negative feedback loop confining disease progression.     

Loss of IFN-gamma enables the expansion of autoreactive CD4+ T cells to induce experimental autoimmune encephalomyelitis by a nonencephalitogenic myelin variant antigen

MHC variant peptides are analogues of immunogenic peptides involving alterations of the MHC-binding residues, thereby altering the affinity of the peptide for the MHC molecule. Recently, our laboratory demonstrated that immunization of WT B6 mice with 45D, a low-affinity MHC variant peptide of MOG(35-55), results in significantly attenuated experimental autoimmune encephalomyelitis (EAE), yet IFN-gamma production is comparable to myelin oligodendrocyte glycoprotein (MOG)(35-55)-immunized mice. In light of these findings, we asked whether IFN-gamma was required for the reduced encephalitogenicity of the weak ligand 45D in EAE. In this study, we report that immunization of mice deficient in IFN-gamma or its receptor with 45D exhibit significant EAE signs compared with 45D-immunized wild-type B6 mice. Moreover, 45D-immunized IFN-gamma(-/-) and IFN-gammaR(-/-) mice demonstrate MOG tetramer-positive CD4(+) T cells within the CNS and display substantial numbers of MOG-specific CD4(+) T cells in the periphery. In contrast, wild-type mice immunized with 45D exhibit reduced numbers of MOG-specific CD4(+) T cells in the periphery and lack MOG tetramer- positive CD4(+) T cells in the CNS. Importantly, the increased encephalitogenicity of 45D in mice lacking IFN-gamma or IFN-gammaR was not due to deviation toward an enhanced IL-17-secreting phenotype. These findings demonstrate that IFN-gamma significantly attenuates the encephalitogenicity of 45D and are the first to highlight the importance of IFN-gamma signaling in setting the threshold level of responsiveness of autoreactive CD4(+) T cells to weak ligands.     

In vivo generation of pathogen-specific Th1 cells in the absence of the IFN-gamma receptor

The precise mechanisms that govern the commitment of CD4 T cells to become Th1 or Th2 cells in vivo are incompletely understood. Recent experiments demonstrate colocalization of the IFN-gammaR chains with the TCR during activation of naive CD4 T cells, suggesting that association of these molecules may be involved in determining lineage commitment. To test the role of IFN-gamma and its receptor in the generation of Th1 Ag-specific CD4 T cells, we analyzed mice after infection with Listeria monocytogenes or lymphocytic choriomeningitis virus. In the absence of IFN-gamma, Ag-specific CD4 T cells were generated in response to both these infections. In addition, IFN-gamma-producing (Th1) Ag-specific CD4 T cells were generated in mice lacking the ligand-binding chain of the IFN-gammaR (IFN-gammaR1-/-) or the signaling chain (IFN-gammaR2-/-). There was no increase in the number of IL-4-producing Ag-specific CD4 T cells, nor was there a decrease in the expression of T-bet in the absence of functional IFN-gamma signaling, indicating that the cells were committed Th1 cells. Thus, both chains of the IFN-gammaR are dispensable for the generation of Th1 Ag-specific CD4 T cells after infection in vivo.     

Treatment of experimental autoimmune prostatitis in nonobese diabetic mice by the vitamin D receptor agonist elocalcitol

On the basis of on the marked inhibitory activity of the vitamin D receptor agonist Elocalcitol on basal and growth factor-induced proliferation of human prostate cells and on its potent anti-inflammatory properties, we have tested its capacity to treat experimental autoimmune prostatitis (EAP) induced by injection of prostate homogenate-CFA in nonobese diabetic (NOD) mice. Administration of Elocalcitol, at normocalcemic doses, for 2 wk in already established EAP significantly inhibits the intraprostatic cell infiltrate, leading to a profound reduction in the number of CD4(+) and CD8(+) T cells, B cells, macrophages, dendritic cells, and I-A(g7)-positive cells. Immunohistological analysis demonstrates reduced cell proliferation and increased apoptosis of resident and infiltrating cells. Significantly decreased production of the proinflammatory cytokines IFN-gamma and IL-17 is observed in prostate-draining lymph node T cells from Elocalcitol-treated NOD mice stimulated by TCR ligation. In addition, Elocalcitol treatment reduces IFN-gamma production by prostate-infiltrating CD4(+) T cells and draining lymph node T cells specific for an immunodominant peptide naturally processed from prostate steroid-binding protein, a prostate-specific autoantigen. Finally, CD4(+) splenic T cells from Elocalcitol-treated NOD mice show decreased ability, upon adoptive transfer into NOD.SCID recipients, to induce autoimmune prostatitis, paralleled by a reduced capacity to produce IFN-gamma in response to prostate steroid-binding protein. The results indicate that Elocalcitol is able to interfere with key pathogenic events in already established EAP in the NOD mouse. These data show a novel indication for vitamin D receptor agonists and indicate that treatment with Elocalcitol may inhibit the intraprostatic inflammatory response in chronic prostatitis/chronic pelvic pain syndrome patients.     

Fas ligand is responsible for CXCR3 chemokine induction in CD4+ T cell-dependent liver damage

Immune-mediated hepatic damage has been demonstrated in the pathogenesis of hepatitis C virus (HCV) and other hepatotrophic infections. Fas/Fas ligand (FasL) interaction plays a critical role in immune-mediated hepatic damage. To understand the molecular mechanism(s) of FasL-mediated liver inflammation, we examined the effect of CD4(+) T cells expressing high levels of FasL on the initiation of hepatic damage through analysis of chemokine and chemokine receptor expression in HCV core x TCR (DO11.10) double-transgenic mice. In vivo antigenic stimulation triggers a marked influx of core-expressing Ag-specific CD4(+) T cells into the liver of the immunized core(+) TCR mice but not their core(-) TCR littermates. Strikingly, the inflammatory process in the liver of core(+) TCR mice was accompanied by a dramatic increase in IFN-inducible protein 10 and monokine induced by IFN-gamma production. The intrahepatic lymphocytes were primarily CXCR3-positive and anti-CXCR3 Ab treatment abrogates migration of CXCR3(+) lymphocytes into the liver and hepatic damage. Importantly, the blockade of Fas/FasL interaction reduces the expression of IFN-inducible protein 10 and monokine induced by IFN-gamma and cellular infiltration into the liver. These findings suggest that activated CD4(+) T cells with elevated FasL expression are involved in promoting liver inflammation and hepatic damage through the induction of chemokines.     

A role for CD44 in the production of IFN-gamma and immunopathology during infection with Toxoplasma gondii

The interaction of activated CD44 with its ligand, low m.w. hyaluronan, is involved in inflammation, but no role has been identified for this interaction in the regulation of an immune response to infection. In these studies, infection of C57BL/6 mice with Toxoplasma gondii resulted in increased expression of CD44 on T cells, B cells, NK cells, and macrophages, and a small percentage of CD4(+) T cells express an activated form of CD44. Administration of anti-CD44 to infected mice prevented the development of a CD4(+) T cell-dependent, infection-induced inflammatory response in the small intestine characterized by the overproduction of IFN-gamma. The protective effect of anti-CD44 treatment was associated with reduced production of IFN-gamma, but not IL-12, in vivo and in vitro. Furthermore, the addition of low m.w. hyaluronan to cultures of splenocytes or purified CD4(+) T cells from infected mice resulted in the production of high levels of IFN-gamma, which was dependent on IL-12 and TCR stimulation. Together, these results identify a novel role for CD44 in the regulation of IFN-gamma production by CD4(+) T cells during infection and demonstrate a role for CD44 in the regulation of infection-induced immune pathology.     

Key roles of CD4+ T cells and IFN-gamma in the development of abdominal aortic aneurysms in a murine model

Abdominal aortic aneurysm (AAA) is one of a number of diseases associated with a prominent inflammatory cell infiltrate and local destruction of structural matrix macromolecules. This inflammatory infiltrate is predominately composed of T lymphocytes and macrophages. Delineating specific contribution of these inflammatory cells and their cytokines in AAA formation is the key to understanding AAA and other chronic inflammatory disease processes. Our previous studies have demonstrated that macrophages are the major source of matrix metalloproteinase-9, which is required for aneurysmal degeneration in the murine AAA model. However, the role of CD4(+) T cells, the most abundant infiltrates in aneurysmal aortic tissue, is uncertain. In the present study, we found that in the absence of CD4(+) T cells, mice are resistant to aneurysm induction. Previous studies have shown that IFN-gamma levels are increased in AAA. IFN-gamma is a main product of T cells. Intraperitoneal IFN-gamma was able to partially reconstitute aneurysms in CD4(-/-) mice. Furthermore, mice with a targeted deletion of IFN-gamma have attenuation of MMP expression and inhibition of aneurysm development. Aneurysms in IFN-gamma(-/-) mice can be reconstituted by reinfusion of competent splenocytes from the corresponding wild-type mice. This study demonstrates the pivotal role that T cells and the T cell cytokine, IFN-gamma, play in orchestrating matrix remodeling in AAA. This study has important implications for other degenerative diseases associated with matrix destruction.     

Cutting edge: CD8+ effector T cells reject tumors by direct antigen recognition but indirect action on host cells

CD8(+) effector T cells recognize malignant cells by monitoring their surface for the presence of tumor-derived peptides bound to MHC class I molecules. In addition, tumor-derived Ags can be cross-presented to CD8(+) effector T cells by APCs. IFN-gamma production by CD8(+) T cells is often critical for tumor rejection. However, it remained unclear whether 1) CD8(+) T cells secrete IFN-gamma in response to Ag recognition on tumor cells or APCs and 2) whether IFN-gamma mediates its antitumor effect by acting on host or tumor cells. We show in this study that CD8(+) effector T cells can reject tumors in bone marrow-chimeric mice incapable of cross-presenting Ag by bone marrow-derived APCs and that tumor rejection required host cells to express IFN-gammaR. Together, CD8(+) effector T cells recognize Ag directly on tumor cells, and this recognition is sufficient to reject tumors by IFN-gamma acting on host cells.     

Dynamic regulation of IFN-gamma signaling in antigen-specific CD8+ T cells responding to infection

IFN-gamma plays a critical role in the CD8(+) T cell response to infection, but when and if this cytokine directly signals CD8(+) T cells during an immune response is unknown. We show that naive Ag-specific CD8(+) T cells receive IFN-gamma signals within 12 h after in vivo infection with Listeria monocytogenes and then become unresponsive to IFN-gamma throughout the ensuing Ag-driven expansion phase. Ag-specific CD8(+) T cells regain partial IFN-gamma responsiveness throughout the contraction phase, whereas the memory pool exhibits uniform, but reduced, responsiveness that is also modulated during the secondary response. The responsiveness of Ag-specific CD8(+) T cells to IFN-gamma correlated with modulation in the expression of IFN-gammaR2, but not with IFN-gammaR1 or suppressor of cytokine signaling-1. This dynamic regulation suggests that early IFN-gamma signals participate in regulation of the primary CD8(+) T cell response program, but that evading or minimizing IFN-gamma signals during expansion and the memory phase may contribute to appropriate regulation of the CD8(+) T cell response.     

Florid pulmonary inflammatory responses in mice vaccinated with Antigen-85 pulsed dendritic cells and challenged by aerosol with Mycobacterium tuberculosis

Mice immunized by the intranasal route with dendritic cells harvested from the lungs and then pulsed with Ag85 (LDC-Ag85) were able to prime naive CD4(+) T cells in vivo. As a result splenic CD4(+) T cells from these immunized mice were able to produce IFNgamma following culture with Mycobacterium tuberculosis-infected antigen presenting cells. Hematoxylin and eosin stained lung sections from LDC-Ag85 immunized mice after they had been exposed to aerosol challenge with M. tuberculosis showed a florid infiltration of macrophages and lymphocytes into granulomas and parenchymal tissues when compared to lung sections from control groups implanted with dendritic cells pulsed with ovalbumin. In addition, using immunohistochemistry, these tissues appeared to have more CD4(+) and CD8(+) cells than the control groups. This was confirmed by flow cytometric analysis which showed that lung cell digests contained increased numbers of CD4 and CD8 interferongamma secreting cells. Despite this increase however, no evidence was seen that indicated that the LDC-Ag85 immunized mice were more resistant to M. tuberculosis infection than mice immunized with LDC pulsed with an irrelevant protein. Instead, the potent inflammatory response in the LDC-Ag85 resulted in serious consolidation of the lung tissue.     

The role of CD1d in the immune response against Listeria infection

To address the role of CD1d in mucosal immune regulation in bacterial infection, we infected CD1d KO mice with Listeria monocytogenes (Lm). A higher systemic bacterial burden associated with inflammatory lymphocytic infiltrations within the intestine was found in CD1d KO compared with wild type (WT) mice. Lm induced strong IFN-gamma mRNA expression in the liver of WT and the intestine of CD1d KO mice, thus demonstrating the dual, opposing immune activities of IFN-gamma in Lm infection that is dependent on CD1d and/or NKT cells. Analysis of hepatic T cell population demonstrated a reduction of NK1.1(+)TCRbeta+ cells in both mice, followed by recovery only in WT mice. Last, the proportion of alpha4beta1 integrin on lung lymphocytes from CD1d KO was dramatically increased compared with WT mice. Thus, the absence of CD1d resulted in increased susceptibility towards Listeria infection, induced changes in NKT cells, and increased trafficking of alpha4beta1 molecule to inflamed lung.     

TNF regulates chemokine induction essential for cell recruitment, granuloma formation, and clearance of mycobacterial infection

Host immunity to mycobacterial infection is dependent on the activation of T lymphocytes and their recruitment with monocytes to form granulomas. These discrete foci of activated macrophages and lymphocytes provide a microenvironment for containing the infection. The cytokine, TNF, is essential for the formation and maintenance of granulomas, but the mechanisms by which TNF regulates these processes are unclear. We have compared the responses of TNF-deficient (TNF(-/-)) and wild-type C57BL/6 mice to infection with Mycobacterium smegmatis, a potent inducer of TNF, and virulent Mycobacterium tuberculosis to delineate the TNF-dependent and -independent components of the process. The initial clearance of M. smegmatis was TNF independent, but TNF was required for the early expression of mRNA encoding C-C and C-X-C chemokines and the initial recruitment of CD11b(+) macrophages and CD4(+) T cells to the liver during the second week of infection. Late chemokine expression and cell recruitment developed in TNF(-/-) mice associated with enhanced Th1-like T cell responses and mycobacterial clearance, but recruited leukocytes did not form tight granulomas. Infection of TNF(-/-) mice with M. tuberculosis also resulted in an initial delay in chemokine induction and cellular recruitment to the liver. Subsequently, increased mRNA expression was evident in TNF(-/-) mice, but the loosely associated lymphocytes and macrophages failed to form granulomas and prevent progressive infection. Therefore, TNF orchestrates early induction of chemokines and initial leukocyte recruitment, but has an additional role in the aggregation of leukocytes into functional granulomas capable of controlling virulent mycobacterial infection.     

A CD8+ T cell heptaepitope minigene vaccine induces protective immunity against Chlamydia pneumoniae

An intact T cell compartment and IFN-gamma signaling are required for protective immunity against Chlamydia. In the mouse model of Chlamydia pneumoniae (Cpn) infection, this immunity is critically dependent on CD8(+) T cells. Recently we reported that Cpn-infected mice generate an MHC class I-restricted CD8(+) Tc1 response against various Cpn Ags, and that CD8(+) CTL to multiple epitopes inhibit Cpn growth in vitro. Here, we engineered a DNA minigene encoding seven H-2(b)-restricted Cpn CTL epitopes, the universal pan-DR epitope Th epitope, and an endoplasmic reticulum-translocating signal sequence. Immunization of C57BL/6 mice with this construct primed IFN-gamma-producing CD8(+) CTL against all seven CTL epitopes. CD8(+) T cell lines generated to minigene-encoded CTL epitopes secreted IFN-gamma and TNF-alpha and exhibited CTL activity upon recognition of Cpn-infected macrophages. Following intranasal challenge with Cpn, a 3.6 log reduction in mean lung bacterial numbers compared with control animals was obtained. Using a 20-fold increase in the Cpn challenging dose, minigene-vaccinated mice had a 60-fold reduction in lung bacterial loads, compared with controls. Immunization and challenge studies with beta(2)-microglobulin(-/-) mice indicated that the reduction of lung Cpn burdens was mediated by the MHC class I-dependent CD8(+) T cells to minigene-included Cpn CTL epitopes, rather than by pan-DR epitope-specific CD4(+) T cells. This constitutes the first demonstration of significant protection achieved by immunization with a CD8(+) T cell epitope-based DNA construct in a bacterial system and provides the basis for the optimal design of multicomponent anti-Cpn vaccines for humans.     

Early resolution of herpes simplex virus type 2 infection of the murine genital tract involves stimulation of genital parenchymal cells by gamma interferon

Early clearance of a thymidine kinase-deficient strain of herpes simplex virus type 2 from the female genital tract required T-cell-produced gamma interferon (IFN-gamma). Transfer of activated CD8+ T cells to irradiated C57BL/6 mice resulted in rapid virus clearance, but clearance was greatly delayed in recipients deficient in the IFN-gamma receptor (IFN-gammaR). Early virus clearance was demonstrated in radiation chimeras in which IFN-gammaR expression was limited to parenchymal cells, but resolution was significantly delayed in chimeras deficient in IFN-gammaR expression and chimeras expressing IFN-gammaR only on hematopoietic cells. Together, these results suggest that early IFN-gamma-mediated protection was manifested mainly by stimulation of genital parenchymal cells.     

Ectopic CD40 ligand expression on B cells triggers intestinal inflammation

Several studies indicate that CD4(+) T cells, macrophages, and dendritic cells initially mediate intestinal inflammation in murine models of human inflammatory bowel disease. However, the initial role of B cells in the development of intestinal inflammation remains unclear. In this study we present evidence that B cells can trigger intestinal inflammation using transgenic (Tg) mice expressing CD40 ligand (CD40L) ectopically on B cells (CD40L/B Tg). We demonstrated that CD40L/B Tg mice spontaneously developed severe transmural intestinal inflammation in both colon and ileum at 8-15 wk of age. In contrast, CD40L/B TgxCD40(-/-) double-mutant mice did not develop colitis, indicating the direct involvement of CD40-CD40L interaction in the development of intestinal inflammation. The inflammatory infiltrates consisted predominantly of massive aggregated, IgM-positive B cells. These mice were also characterized by the presence of anti-colon autoantibodies and elevated IFN-gamma production. Furthermore, although mice transferred with CD4(+) T cells alone or with both CD4(+) T and B220(+) B cells, but not B220(+) cells alone, from diseased CD40L/B Tg mice, develop colitis, mice transferred with B220(+) B cells from diseased CD40L/B Tg mice and CD4(+) T cells from wild-type mice also develop colitis, indicating that the Tg B cells should be a trigger for this colitis model, whereas T cells are involved as effectors. As it has been demonstrated that CD40L is ectopically expressed on B cells in some autoimmune diseases, the present study suggests the possible contribution of B cells in triggering intestinal inflammation in human inflammatory bowel disease.     

A novel role of CD30L/CD30 signaling by T-T cell interaction in Th1 response against mycobacterial infection

A CD30 ligand (CD30L, CD153) is a type II membrane-associated glycoprotein belonging to the TNF family. To illustrate the potential role of CD30L in CD4(+) Th1 cell responses, we investigated the fate of Ag-specific CD4(+) T cells in CD30L-deficient (CD30L(-/-)) mice after Mycobacterium bovis bacillus Calmette-Guérin (BCG) infection. The number of bacteria was significantly higher in organs of CD30L(-/-) mice than in wild-type (WT) mice 4 wk postinfection. The numbers of purified protein derivative- or Ag85B-specific-IFN-gamma-producing-CD4(+) T cells in spleen, lung, or peritoneal exudate cells were significantly fewer in CD30L(-/-) mice than in WT mice. During the infection, CD30L was expressed mainly by CD44(+)CD3(+)CD4(+) T cells but not by CD3(+)CD8(+) T cells, B cells, dendritic cells, or macrophages. Costimulation with agonistic anti-CD30 mAb or coculturing with CD30L-transfected P815 cells restored IFN-gamma production by CD4(+) T cells from BCG-infected CD30L(-/-) mice. Coculturing with CD30L(+/+)CD4(+) T cells from BCG-infected WT mice also restored the number of IFN-gamma(+)CD30L(-/-)CD4(+) T cells. When transferred into the CD30L(+/+) mice, Ag-specific donor CD30L(-/-) CD4(+) T cells capable of producing IFN-gamma were restored to the compared level seen in CD30L(+/+) CD4(+) T cells on day 10 after BCG infection. When naive CD30L(+/+) T cells were transferred into CD30L(-/-) mice, IFN-gamma-producing-CD4(+) Th1 cells of donor origin were normally generated following BCG infection, and IFN-gamma-producing-CD30L(-/-)CD4(+) Th1 cells of host origin were partly restored. These results suggest that CD30L/CD30 signaling executed by CD30(+) T-CD30L(+) T cell interaction partly play a critical role in augmentation of Th1 response capable of producing IFN-gamma against BCG infection.