Cytoplasmic antigens from Nocardia elicting a specific delayed hypersensitivity.

Purified cytoplasmic extracts from Nocardia asteroides and N. brasiliensis elicit delayed hypersensitivity in Nocardia-sensitized guinea pigs. The differences in skin reactivity clearly show that it is possible to distinguish between different Nocardia species. When peritoneal exudate cells from the latter animals were obtained and treated with the purified cytoplasmic extracts, their migration was inhibited to a significant degree only by means of the homologous antigen. A mild delayed reactivity was observed when the cytoplasmic antigens were used as skin test materials on animals sensitized with BCG. On the other hand, no inhibition of migration was observed when peritoneal exudate cells from BCG-sensitized guinea pigs were exposed to the cytoplasmic antigens.