EXPANSION OF GAMMA-DELTA(-CELLS IN BALB() T)C MICE INFECTED WITH LEISHMANIA-MAJOR IS DEPENDENT UPON TH2-TYPE CD4(+) T-CELLS/

T cells belong to either the alpha beta(+), gamma delta(+) lineage as defined by their antigen receptor. Although both T-cell subsets have b een shown to be involved in the immune response to the parasite Leishm ania major, very little is known about possible interactions between t hese two populations. In this study, using a mouse model of infection with L. major, we showed that expansion of a subset of gamma delta(+) T cells in vivo is dependent upon the presence of alpha beta(+) CD4(+) T cells. Moreover, this effect appears to be mediated via the secreti on of lymphokines by CD4(+) cells with a T-helper 2 (Th2) functional p henotype. Results showing that activation of Th2-type cells in mice tr eated with anti-immunoglobulin D antibodies or infected with Nippostro ngylus brasiliensis also results in gamma delta(+) T-cell expansion su ggest that this effect of the Th2-type CD4(+) cells is a general pheno menon not restricted to infection with L. major.