Interferon-gamma and interleukin-4 responses in relation to serum IgE levels in persons infected with human T lymphotropic virus type I and Strongyloides stercoralis.

Possible immunologic interaction between infection with human T lymphotropic virus type 1 (HTLV-1), a retrovirus, and the intestinal parasite Strongyloides stercoralis was investigated in persons infected with one or both agents. This was done by examining the cytokine responses of peripheral blood mononuclear cells (PBMC) to mitogens and Strongyloides antigen. PBMC of subjects infected with HTLV-1 spontaneously produced interferon (IFN)-gamma with levels that correlated inversely with serum IgE levels. HTLV-1-infected subjects also had poor interleukin (IL)-4 responses to mitogenic stimulation, unlike persons without HTLV-1 infection. It is postulated that the IFN-gamma produced by activated T cells in some HTLV-1-infected persons acts to down-regulate IL-4 with consequent reduction of serum IgE levels. The impaired IgE responses and other effects of IL-4 down-regulation may be contributing factors to more severe disease and impaired response to treatment of strongyloidiasis in some HTLV-1-infected persons.