H-2-controlled, dose-dependent suppression of the response that expels adult Trichinella spiralis from the small intestine of mice.

H-2 congenic strains of mice expressing the H-2k, H-2q or H-2f haplotype were tested for their ability to expel Trichinella spiralis from the gut following infection with either 100, 150, 200, 400, 500, or 600 L1 infective larvae. H-2q and H-2f mice expelled worms more quickly than H-2k mice when 100-200 L1 larvae were given, but this H-2-controlled effect was much reduced when mice received 400 L1 larvae, and completely eliminated when 500 or 600 L1 larvae were given. The observed dose-dependent delay in the expulsion response was paralleled by a concurrent suppression of lymphocyte responsiveness. Lymphocytes from H-2q mice infected with 100-200 L1 larvae incorporated more [3H]thymidine than did cells from H-2k mice. However, this H-2-controlled difference was not apparent in cells from mice receiving 400-600 L1 larvae. The strongest proliferation response in each case was associated with mice infected with the smallest number of worms. Since strains of mice expressing H-2q or H-2f alleles were suppressed at high doses to a much greater extent than were mice expressing H-2k, H-2 genes must influence this dose-dependent response. Many earlier studies, which failed to demonstrate marked H-2 effects on immunity to T. spiralis, employed infective doses which are shown here to be preferentially suppressive to otherwise resistant strains of mice.