A striking increase in rod-cored vesicles in pit cells (natural killer cells) and augmentation of the liver-associated natural killer activity by a streptococcal preparation (OK-432)

OK-432, a streptococcal preparation, induced a marked increase in the number of rodcored vesicles in pit cells (natural killer cells) of the rat liver. OK-432 enhanced also the liver-associated natural killer activity. OK-432 injected intravenously was incorporated into lysosomes ofKupffer cells. Kupffer cells and pit cells were increased in their number and were in wide contact with each other. Prominent Golgi complex and many rodcored vesicles characterized the actively secreting pit cells. No obvious morphological changes were detected in dense granules in pit cells. It is suggested that the increment of rod-cored vesicles induced by OK-432 is responsible for the augmentation of the liverassociated natural killer activity. ' !_ 3 ' ,.:_._. II$I I: ~43. __ 2' -; <; ~' ; \ . ' ' P-) 1 ' " -. ' =" -\ e s \' : ..' _' :*. ._~'.