Delayed hypersensitivity in man: a correlate in vitro and transfer by an RNA extract.

The migration of sensitized human monocytic-phagocytic cells from lymph-node tissue-culture suspensions was regularly and specifically inhibited by purified protein derivative or histoplasmin. Moreover, when nonsensitive cells were incubated with an RNA extract from lymph nodes of donors sensitive to purified protein derivative, histoplasmin, or both, the migration of these cells was specifically inhibited by these antigens. Ribonuclease inactivated the RNA extract.