Production of IFN- by CD4+ T cells in response to malaria antigens is IL-2 dependent

T-cell immune responses are critical for protection of the host and for disease pathogenesis during infection with Plasmodium species. We examined the regulation of CD4+ T-cell cytokine responses during infection with Plasmodium berghei ANKA (PbA). CD4+ T cells from PbA-infected mice produced IFN-γ, IL-4 and IL-10 in response to TCR stimulation at levels higher than those from uninfected mice. This altered cytokine response was dependent on parasitemia. To examine the specificity of the response, mice were adoptively transferred with CD4+ T cells from OT-II TCR transgenic mice and were infected with PbA expressing OVA. Unexpectedly, CD4+ T cells from the OT-II-transferred wild-type PbA-infected mice showed high levels of IFN-γ production after stimulation with OVA and the cells producing IFN-γ were not OT-II but were host CD4+ T cells. Further investigation revealed that host CD4+ T cells produced IFN-γ in response to IL-2 produced by activated OT-II cells. This IFN-γ response was completely inhibited by anti-CD25 mAbs, and this effect was not due to the block of the survival signals provided by IL-2. Furthermore, IFN-γ production by CD4+ T cells in response to PbA antigens was dependent on IL-2. These findings suggest the importance of IL-2 levels during infection with malaria parasites and indicate that CD4+ T cells can produce IFN-γ without TCR engagement via a bystander mechanism in response to IL-2 produced by other activated CD4+ T cells

Recruitment of distinct immune cell populations to the lung after intratracheal TLR4 signaling activation by two different stimulations

The toll-like receptor 4 (TLR4)-mediated immune response is considered as one of the triggers of acute respiratory distresssyndrome. The agonistic monoclonal antibody UT12 specific for the TLR4/MD2 complex induces immune activation in a mannerdistinct from lipopolysaccharide (LPS). In order to compare the effects of this differential TLR4 signaling activation, we examinedimmune cell recruitment to the lung following intratracheal inoculation with UT12 and LPS in mice. The increase in pulmonaryneutrophils was much higher after LPS treatment compared with UT12 treatment, while CD11bhiCD11＋cells increased to similarlevels following both treatments. These changes were MyD88-dependent and TRIF-independent. These differential effects onimmune cell recruitment to the lung suggest distinct underlying mechanisms in response to TLR4 stimulation. These findingsfurther indicate that TLR signaling can lead to different outcomes depending on the ligand and activation pathway, which mayrelate to the complex pathogenesis of inflammatory lung diseases

マラリア感染と治療を繰り返すことにより制御性のCD19陽性B細胞が生じ実験的脳マラリアの発症が抑制される

In African endemic area, adults are less vulnerable to cerebral malaria than children probably because of acquired partial immunity or semi-immune status. Here, we developed an experimental cerebral malaria (ECM) model for semi-immune mice. C57BL/6 (B6) mice underwent one, two and three cycles of infection and radical treatment (1-cure, 2-cure and 3-cure, respectively) before being finally challenged with 104 Plasmodium berghei ANKA without treatment. Our results showed that 100% of naive (0-cure), 67% of 1-cure, 37% of 2-cure and none of 3-cure mice succumbed to ECM within 10 days post challenge infection. In the protected 3-cure mice, significantly higher levels of plasma IL-10 and lower levels of IFN-γ than the others on day 7 post challenge infection were observed. Major increased lymphocyte subset of IL-10 positive cells in 3-cure mice was CD5(?)CD19(+) B cells. Passive transfer of splenic CD19(+) cells from 3-cure mice protected naive mice from ECM. Additionally, aged 3-cure mice were also protected from ECM 12 and 20 months after the last challenge infection. In conclusion, mice became completely resistant to ECM after three exposures to malaria. CD19(+) B cells are determinants in protective mechanism of semi-immune mice against ECM possibly via modulatory IL-10 for pathogenic IFN-γ production.長崎大学学位論文 学位記番号:博(医歯薬)甲第611号 学位授与年月日:平成25年8月7日Author： Lam Quoc Bao , Nguyen Tien Huy , Mihoko Kikuchi, Tetsuo Yanagi, Masachika Senba, Mohammed Nasir Shuaibu, Kiri Honma, Katsuyuki Yui, Kenji HirayamaCitation: PLoS ONE, 8(5), e64836; 2013Nagasaki University (長崎大学)課程博

Characterization of waves of leukocyte recruitment to the lung allograft and the effect of CTLA4-Ig

MHC-mismatched lung allografts are rapidly rejected by the host immune response. We analyzed cells infiltrating the grafted lung tissue using a collagenase-digestion method. The grafted lung was filled with host-derived leukocytes as early as day 1 post transplantation and the majority of the initial infiltrating cells were granulocytes. This initial influx of granulocytes waned rapidly, followed by a steady increase in lymphocytes, particularly T cells, and then by macrophages. The proportion of CD4+ T cells that express CD25 were increased in the graft the majority of which were activated CD4+ cells. We applied cytotoxic T-lymphocyte-associated antigen 4 (CTLA4)-Ig treatment in combination with donor-specific blood transfusion to the transplantation of lung allograft, which was significantly prolonged by the treatment. To examine the cellular and molecular basis of the inhibition of the graft rejection, we evaluated number and cytokine mRNA expression of the cells infiltrating in the lung allograft using collagenase-digestion method, although we were unable to detect significant effects of the treatment. Taken together, this study demonstrates that single cell suspensions from cellular infiltrates of lung tissue is useful for phenotypical and functional studies on cells infiltrating lung tissue after graft transplantation

Interferon regulatory factor-4 activates IL-2 and IL-4 promoters in cooperation with c-Rel.

Interferon regulatory factor (IRF)-4 is a member of the IRF transcription factor family, whose expression is primarily restricted to lymphoid and myeloid cells. In T-cells, IRF-4 expression is induced by T-cell receptor (TCR) cross-linking or treatment with phorbol-12-myristate-13-acetate (PMA)/Ionomycin, and IRF-4 is thought to be a critical factor for various functions of T-cells. To elucidate the IRF-4 functions in human adult T-cell leukemia virus type 1 (HTLV-1)-infected T-cells, which constitutively express IRF-4, we isolated IRF-4-binding proteins from T-cells, using a tandem affinity purification (TAP)-mass spectrometry strategy. Fourteen proteins were identified in the IRF-4-binding complex, including endogenous IRF-4 and the nuclear factor-kappaB (NF-κB) family member, c-Rel. The specific association of IRF-4 with c-Rel was confirmed by immunoprecipitation experiments, and IRF-4 was shown to enhance the c-Rel-dependent binding and activation of the interleukin-4 (IL-4) promoter region. We also demonstrated that IL-2 production was also enhanced by exogenously-expressed IRF-4 and c-Rel in the presence of P/I, in T-cells, and that the optimal IL-2 and IL-4 productions in vivo was IRF-4-dependent using IRF-4-/- mice. These data provide molecular evidence to support the clinical observation that elevated expression of c-Rel and IRF-4 is associated with the prognosis in adult T-cell leukemia/lymphoma (ATLL) patients, and present possible targets for future gene therapy

Merozoite Surface Protein 1-Specific Immune Response Is Protective against Exoerythrocytic Forms of Plasmodium yoelii

One of the difficulties in developing an effective malaria vaccine is the antigenic change of the parasite during the life cycle. It is desirable that vaccine-induced protective immunity be effective at different stages of parasite development. Merozoite surface protein 1 (MSP1) is a candidate vaccine antigen against blood-stage malaria, but it is also expressed in the exoerythrocytic forms. It was not known, however, whether the anti-MSP1 immune response is effective against the liver-stage malaria parasite. We generated a recombinant protein of MSP1 fused to heat-shock cognate protein 70 (hsc70) and studied its vaccination effect. When C57BL/6 mice were immunized with the fusion protein prior to challenge infection with Plasmodium yoelii sporozoites, the onset of parasitemia was delayed or no parasitemia was observed. To determine whether this was due to the protective immunity against liver-stage parasites, P. yoelii-specific rRNA in the infected liver was quantitated by real-time reverse transcription-PCR analysis. The level of parasite-specific rRNA was reduced in mice immunized with the fusion protein of MSP1 and hsc70 but not with hsc70 alone, indicating that MSP1-specific immunity can be protective against the exoerythrocytic form of the parasite. Furthermore, the adoptive transfer experiments of immune lymphocytes and serum into naive mice suggested that the protective immunity was dependent on cellular and not humoral immunity. Finally, the vaccine-induced protection was also observed in A/J, C3H, and BALB/c mice, suggesting that MSP1-specific protective immunity at the exoerythrocytic stage can be induced in animals over a wide range of genetic backgrounds