Marine CD4(+) T lymphocyte subsets and host defense against Pneumocystis carinii

The recruitment of specific subsets of CD4(+) T lymphocytes to the lungs in response to Pneumocystis carinii was investigated. For mice inoculated wit h P. carinii, an ELISPOT assay was used to calculate the numbers of lymph n ode and lung tissue CD4(+) cells that secreted interferon (IFN)-gamma (Th1 cytokine) and interleukin (IL)-4 (Th2 cytokine) after concanavalin A stimul ation. An ELISA was used to assay culture supernatants for cytokine concent rations. Precursor frequency of both IFN-gamma- and IL-4-secreting cells wa s increased in lymph nodes at 1 week, whereas increases in Th1 and Th2 cell s in lung tissue were delayed 3 weeks before declining. The frequency of IL -4-secreting cells always was greater than the frequency of IFN-gamma secre ting cells. These results demonstrate an early T lymphocyte response in dra ining lymph nodes, followed by later recruitment of Th1 and Th2 lymphocytes into lung tissue. The overall CD4(+) T cell response to P. carinii involve s both Th1 and Th2 subsets, but the response is Th2 dominant in both lymph node and lung tissue.