Immunologic correlates of the hyperresponsive syndrome of loiasis.

The usual clinical picture of loiasis in long-term visitors to endemic areas differs from that in residents of these areas, with allergic symptoms, hypergammaglobulinemia, profound hypereosinophilia, and increased serum levels of IgE being more prominent. In further analyzing the immunologic correlates of this apparent hyperreactivity in 20 patients, we have found the following: (1) parasite-specific IgG (in all) and IgE (in some) were extremely elevated in the patients; (2) qualitative analysis by immunoblotting indicated multiple antigens recognized by both IgG and IgE antibodies in these patients; (3) filaria antigen-specific, lymphocyte proliferative immune responses were vigorous in all patients and, in each individual, exceed the response to other soluble antigens; (4) spontaneous and antigen-driven, parasite-specific antibody production in vitro was elevated in all six patients studied; (5) there was a significant increase in the ratio of CD4/CD8+ T cells. These observations suggest that both specific dysregulation of the immune response to the parasite antigen, as well as nonspecific immune activation, accounts for the clinically apparent hyperresponsive state seen in expatriates acquiring loiasis.