Koichi Koyama

Mucosal mast cell responses are not required for protection against infection with the murine nematode parasite Trichuris muris.

Infective forms of Trypanosoma cruzi, the parasite that causes Chagas’ disease, express on their surface an enzyme denominated trans‐sialidase (TS). The present study was designed to evaluate the naturally acquired immune responses to a bacterial recombinant protein representing the catalytic domain of TS in chronically infected chagasic individuals. The cellular immune response was measured by in‐vitro T‐cell proliferation and by interferon (INF)‐g, interleukin (IL)‐4 and IL‐10 production in response to a whole‐parasite homogenate and the recombinant protein. The peripheral blood mononuclear cells of 78·6% of 28 chagasic patients responded to the recombinant protein as estimated by T‐cell proliferation. With respect to cytokine production, 88% of the cells of the chagasic individuals produced IFN‐g on stimulation with the recombinant protein. In contrast, IL‐4 or IL‐10 were minimally produced in response to TS. The cellular immune response was specific because most healthy individuals never exposed to T. cruzi failed to react with this recombinant protein. The plasma of 71·4% or 100% of chagasic patients had IgG antibodies as determined by ELISA or by the presence of TS inhibitory antibodies, respectively. We conclude that the catalytic domain of TS is recognized by IFN‐g producing type 1 cells and antibodies in a large proportion of patients infected with T. cruzi.

The role of CD4+ and CD8+ T cells in protective immunity to the murine nematode parasite Trichuris muris

The role ofCD4+ and CD8+ T cells in protective immunity to Trichuris muris was studied in CD4+ or CD8+ or both CD4+ and CD8+ T cell‐depleted BALB/c mice. To assess in vivo depletion of T‐cell subsets, CD4+ and CD8+ T cells in the Peyers patches, the mesenteric lymph nodes (MLN), and the spleens of mice treated with T cell‐specific monoclonal antibodies (MoAbs) were analysed by FACS. CD4+ T cells were selectively depleted in mice injected with anti‐CD4 MoAb i.p. and injection of anti‐CD8 MoAb resulted in selective depletion ofCD8+ T cells. The expulsion ofl. muris was inhibited in CD4+ T cell‐depleted mice and numerous worms were detected in the large intestine on days 14 and 21 after infection, although no suppression of protective immunity to T. muris was observed in CD8+ T cell‐depleted mice. Moreover, there was no difference in suppression of protective immunity to T. muris between CD4+ T cell‐depleted and both CD4+ and CD8+ T cell‐depleted mice. These results indicate that CD4+ T cells play a central role in protective immunity to T. muris infection.

Comparative studies on immune responses to infection in susceptible B10.BR mice infected with different strains of the murine nematode parasite Trichuris muris

A comparison of immune responses to infection between groups of B10.BR mice infected with different strains of T. muris, S strain (isolated in Sobreda, Portugal), E strain (isolated in Edinburgh), and E‐J strain (originally E strain, which has been maintained in our laboratory, Japan), was performed. In mice infected with E and E‐J strains, most of the worms were expelled by day 32 after infection, though the expulsion was faster in E‐J strain‐infected mice. In contrast, no expulsion was observed in S strain‐infected mice by day 32 and egg production occurred on day 32. IL‐4 production occurred in concanavalin A (Con‐A)‐stimulated mesenteric lymph node cells (MLNC) from B10.BR mice infected with E and E‐J strains, whereas no IL‐4 production was observed in S strain‐infected mice. IL‐4 production did not occur in normal mice. In comparison with normal mice, high levels of IFN‐γ production by Con A‐stimulated MLNC were detected in mice infected with every strain of T. muris. IFN‐γ production in S strain‐infected mice was greater, occurred earlier and was more persistent than in mice infected with E and E‐J strains. IgG1 and IgG2a antibodies to T. muris excretory/secretory antigens were observed in B10.BR mice infected with every strain of T. muris. Antibody production showed similar kinetics. These differences in the expulsion kinetics and IL‐4 production in B10.BR mice infected with S, E, and E‐J strains suggest the involvement of IL‐4 in protection against T. muris infection, and confirm the previous conclusion by Else et al. (1994).

NK1.1+ cell depletion in vivo fails to prevent protection against infection with the murine nematode parasite Trichuris muris.

Protection against the murine nematode parasite Trichuris muris has been shown to involve interleukin 4 (IL‐4). NK1.1+ T cell receptor αβ+ cells, designated Natural Killer T (NKT) cells, produce a large amount of IL‐4 in response to anti‐CD3 stimulation and numerous pieces of evidence suggest that NKT cells provide the initial source of IL‐4 for T helper 2 (Th2) priming. These observations allow the hypothesis that NKT cells produce a large amount of IL‐4 in response to T. muris infection and augment Th2 responses and IL‐4 production, thus achieving protection against T. muris. To investigate the involvement of NKT cells in protection against T. muris infection, NK1.1+ cell‐depleted B10.BR mice were prepared by anti‐NK1.1 monoclonal antibody injection. Efficient expulsion of T. muris worms occurred in NK1.1+ cell‐depleted infected mice, and the expulsion kinetics of T. muris worms, the levels of IL‐4 production by mesenteric lymph node cells, and the kinetics of the specific IgG1 and IgG2a responses to T. muris were similar to those in mouse IgG‐treated or non‐treated control B10.BR mice. These observations suggest that NK1.1+ cells and NKT cells are not involved in the induction of Th2 responses and protective immunity to T. muris infection.

B-cell activation in the mesenteric lymph nodes of resistant BALB/c mice infected with the murine nematode parasite Trichuris muris.

Abstract Immune responses in resistant BALB/c mice infected with the murine nematode parasite Trichuris muris were examined. Following the establishment of infection, worm burdens of T. muris were expelled by BALB/c mice by day 21 postinfection (p.i.). Specific immunoglobulin G1 (IgG1) antibodies to T. muris excretory/secretory (E/S) antigens were detected in sera from infected mice, though specific IgG2a antibodies were not observed during infection. Ig-producing cells increased in the mesenteric lymph nodes (MLN) of infected mice on days 7, 14, and 21 p.i., with the greatest increase in numbers of IgG- and IgA-producing cells occurring on day 14. Marked increases in the relative percentages of B220+ and surface Ig+ (sIg+) cells were observed in the MLN of infected mice on days 14 and 21 p.i. Furthermore, cellular expansion of the MLN in infected mice resulted in an increase in the absolute numbers of B220+ and sIg+ cells. The levels of interleukin 2 (IL-2), IL-4, and interferon-γ (IFN-γ) detected in the supernatants from concanavalin A-stimulated MLN cells of infected mice were higher than those found in normal mice. Consequently, the expulsion of T. muris in resistant BALB/c mice was concomitant with cytokine production and B-cell activation in the MLN of infected mice. These results suggest the involvement of B-cell responses in protective immunity to T. muris infection.

Dendritic cell expansion occurs in mesenteric lymph nodes of B10.BR mice infected with the murine nematode parasite Trichuris muris

Dendritic cells (DCs) are a crucial element in the immune system and bridge innate and adaptive immunity. CD11c+ B220− DCs residing in Peyer’s patches (PPs) have the ability to produce interleukin 10 (IL-10) and induce T helper (Th2) development. Evidence suggests that CD11c+ B220− DCs maintain the gut environment by suppressing Th1 responses with IL-10, resulting in a Th2-dominat gut environment. Th2 effectors are required for protection against the murine nematode parasite Trichuris muris, and thus CD11c+ B220− DCs may be involved in the induction of Th2 cells in T. muris infection. In the present study, the kinetics of CD11c+ B220− DCs were analyzed in mesenteric lymph nodes of B10.BR mice infected with the E-J isolate of T. muris, and the cellular expansion of CD11c+ B220− DCs was also observed. As well, the DC expansion was consistent with the occurrence of worm expulsion augmented by IL-4 and IL-13. The evidence here suggests the involvement of CD11c+ B220− DCs in protective Th2 responses to T. muris infection.