Increased frequency of Th2-type cytokine-producing T cells in microfilaremic loiasis.

The frequency of cytokine-producing peripheral blood mononuclear cells was assessed in 28 subjects with microfilaremic loiasis and in 14 amicrofilaremic individuals. In addition, a subgroup of seven microfilaremic individuals coinfected with Plasmodium malariae was evaluated. By using flow cytometry for the intracellular detection of cytokines, a more pronounced T helper (Th)2 cell-type response with the expansion of interleukin (IL)-4, IL-10, and IL-13 expressing CD4+ cells in the microfilaremic compared with the amicrofilaremic group was noted. Expression of IL-5 was equivalent in both groups as was the frequency of Th2-type cytokines expressing CD8+ cells and of Th1-type cytokines (interferon [IFN]-gamma, IL-2, IFN-gamma/IL-2) producing CD4+ and CD8+ cells. Th0-type cytokine-expressing cells, represented by IL-4/IFN-gamma, IL-10/IFN-gamma, and IL-13/IFN-gamma, were equally distributed within groups. Coinfection of P. malariae did not significantly alter the cytokine expression compared with microfilaremic individuals without P. malariae infections. By identifying a large panel of cytokine-producing T cell subpopulations, a Th2-driven immune response in microfilaremic Loa loa patients was noted.