SCHISTOSOMA-MANSONI EGG-PRIMED T(H)0 AND T(H)2 CELLS - FAILURE TO DOWN-REGULATE IFN-GAMMA PRODUCTION FOLLOWING IN-VITRO CULTURE

Schistosoma mansoni eggs induce a rapid and pronounced T(h) response w hich, based on cytokine secretion patterns, at day 3 post priming is T (h)0-like and at day 10 is T(h)2-like. To establish whether or not the day-3 cells have been programmed in vivo to develop into T(h)2 cells, they were cultured for 7 days to become in vitro equivalents of day-1 0 in vivo cells. Following this culture period, the population was app roximately 75% CD4+, 22% CD8+, 6% B220+ and capable of producing IL-2, IFN-gamma, IL-4, -5 and -10 upon stimulation. This T(h)0-like status was confirmed by the observations that in response to mitogen IL-4 and IFN-gamma production are both CD4+-cell dependent and that IFN-7 and IL-4 are produced concomitantly by single cells. These data suggest th at T(h)0 cells persist in vivo, but are incapable of secreting IFN-gam ma at day 10 due to an inhibitory factor which does not develop or is labile in vitro. This concept is supported by the surprising observati on that day-10 LN cells, which are T(h)2-like immediately ex-vivo, rap idly gain the ability to secrete IFN-gamma following a short period of culture.