HUMAN CORD-BLOOD T-CELL RECEPTOR-ALPHA-BETA CELL RESPONSES TO PROTEINANTIGENS OF PARACOCCIDIOIDES-BRASILIENSIS YEAST FORMS

Paracoccidioides brasiliensis causes a chronic granulomatous mycosis, prevalent in South America, and cell-mediated immunity represents the principal mode of protection against this fungal infection. We investi gated the response of naive cord blood T cells to P. brasiliensis lysa tes. Our results show: (1) P. brasiliensis stimulates T-cell expansion , interleukin-2 (IL-2) production and differentiation into cytotoxic T cells; (2) T-cell stimulation depends on P. brasiliensis processing a nd major histocompatibility complex (MHC) class II expression; (3) the responsive T-cell population expresses alpha beta T-cell receptors (T CR) with different V beta gene products, CD4 and CD45RO; (4) the P. br asiliensis components involved in T-cell expansion primarily reside in a high molecular weight (100 000 MW) and a low molecular weight (< 10 00 MW) protein fraction. These results indicate that protein antigens of P. brasiliensis stimulate cord blood CD4 alpha beta T cells, indepe ndent from in vivo presensitization, and thus question direct correlat ion of positive in vitro responses with protective immunity in vivo.