NEMATODE INFECTION INDUCES TH2 CELL-ASSOCIATED IMMUNE-RESPONSES IN LEC MUTANT RATS WITH HELPER T-CELL IMMUNODEFICIENCY

Long-Evans Cinnamon (LEC) vats have maturational arrest of CD4(+)8(-) T cells from CD4(+)8(+) cells in the thymus. Despite this, CD4(+)8(-) T cells are always present in peripheral lymphoid organs of LEC rats, suggesting that these CD4(+)8(-) T cells are generated by an uncommon pathway. We investigated the role of LEC rat peripheral CD4(+)8(-) T c ells in Th2-associated responses to infection with the nematode Nippos trongylus brasiliensis. After infection, the numbers of CD4(+)8(-) TCR alpha beta(+) T cells significantly increased in mesenteric lymph non es (MLN) and the spleen, while those in the thymus were still negligib le. Infection also induced significant up-regulation of IL-4 gene expr ession in LEC rat MLN cells. Total serum IgE levels in LEC rats were m arkedly increased two weeks after infection. Mucosal mast cell respons es in the gut and lungs of LEC rats were induced as prominently as in control Long-Evans Agouti (LEA) mts. Faecal egg count data indicated t hat LEC rats rejected nematodes faster than LEA rats. These results su ggested that Th2-associated responses can be induced by nematode infec tion in LEC rats probably through the extrathymic recruitment and prol iferation of CD4(+)8(-) TCR alpha beta(+) T cells.