Suppression of cell-mediated immunity following oral feeding of mice with palmyrah (Borassus flabellifer L) flour.

Inbred mice fed with a 40% mixture of palmyrah flour pellets showed a significantly reduced capacity to mount a delayed-type hypersensitivity (DTH) response to sheep red blood cells (SRBC). Maximal suppression of DTH was noted after 6 days of feeding but was detectable even after 2 days. Maximal suppression occurred when flour feed was maintained into the sensitization period (with SRBC). The suppressive effect was transferable to normal mice fed with pellets ad libitum by viable spleen cells from mice fed with the 40% flour pellet mixture for a period of 2 days. Further characterization of the cells which were able to transfer suppression showed them to be T cells, some of which possess the Ly-1 surface antigen. The cells appear to be negative for Ly-2 surface antigen. Histologically, no evidence of lesions was noted in the liver and other organs of recipient mice which received cells from flour-fed donors. We thus favour the interpretation that oral feeding of mice with palmyrah flour induced the generation of T suppressor cells which were able to suppress the DTH response to SRBC. The significance and implications of these findings are discussed.