Cellular responses in human strongyloidiasis.

Peripheral lymphocytes from 16 patients with chronic uncomplicated strongyloidiasis and 15 non-infected controls were stimulated in vitro with Strongyloides stercoralis larval antigens, other non-parasite antigens and the T cell mitogen phytohemagglutinin (PHA). In the presence of autologous plasma the patients' responses to Strongyloides antigens were similar to those of controls. When lymphocytes from nine patients were cultured in the presence of normal human serum, responses to parasite antigens were enhanced, while responses to other antigens and to PHA were unaffected. Lymphoproliferative responses to PHA were significantly lower in the patients' group than in the controls. These findings suggest that in chronic strongyloidiasis, in addition to a depression of T cell activity, factors are present in the patients' serum that inhibit parasite-specific cellular responses in vitro.