We analyzed the dynamics of splenic T-lymphocyte function in relation to hepatopathologic changes in C3H/Hc mice, experimentally infected with Schistosoma japonicum. Vigorous granuloma formation was observed at 7 wk postinfection. At 10 wk postinfection, granuloma formation entered into the down-modulation stage, as represented by the diminished granuloma size. The Th2 response was activated when eggs appeared in the liver, whereas Th1 responses were depressed and the proliferation of T lymphocytes was decreased. The level of IgG antibodies to the worm and egg antigens rose continually after infection. Interleukin-12 treatment of infected mice inhibited Th2 responses and T-cell proliferation, decreased granuloma formation and fibrosis, but had no effect on the fecundity of the worms. These data suggest that egg deposition is the major factor driving Th2 responses, depressing Th1 cytokine expression as well as T-cell proliferation in S. japonicum-infected mice.

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T cell clones (B1, B21, B7, A25) specific to the soluble egg antigen (SEA) of Schistosoma japonicum were established from C3H/He mice immunized with SEA. These clones belonged to CD3+, CD4+ and CD8-Th1 cells, showing TCR-gamma delta-, TCR-alpha beta+ and Vbeta10b+. The molecular weights of target antigens recognized by the clones ranged from 51 to 80 kDa. Interleukin-2 (IL-2) and IL-12 could vigorously increase the proliferation response of the T clones to SEA; while IL-10 and transforming growth factor-beta1 (TGF-beta1) strongly inhibited the response. IL-12 activity was detected in the culture supernatant of T clones stimulated with SEA in the presence of APC (antigen presenting cells). This stimulation also upregulated the expression of the IL-12 receptor on the T clones. IL-12 from APC served as a costimulatory factor for the SEA induced proliferation of the T clone cells. Clone B1 was able to induce granuloma formation both in vivo and in vitro. These data provide further insight into the complicated interaction among SEA, T cell and cytokine at a clonal level in S. japonicum infection.

A new apparatus for feeding mosquitoes is described. It is constructed without special technique and easy of handling. The usefulness of the apparatus is demonstrated by a report on investigations into the effects of nucleotides on mosquito gorging and the development of the microfilariae from the jird peritoneal cavity and from the dog venous blood in Aedes aegypti. As a phagostimulant 1O-3M ATP is the most effective of the nucleotides tested. The microfilariae from the jird peritoneal cavity have been proved to reach stage III (i.e. infective stage) as those from the dog, although the rate is lower in the former. It is also proved that the microfilariae develop to infective larvae in the mosquitoes which have not taken blood, serum or protein meals.