Allogeneic lymphocyte cytotoxicity in rats: the effects of various pharmacological agents.

In a number of strain combinations among inbred rats, intravenously injected 51Cr-labelled lymphocytes are rapidly destroyed by unsensitized allogeneic hosts. This phenomenon has previously been referred to by a number of terms, the most explicit and least confusing of which is allogeneic lymphocyte cytotoxicity (ALC). It is characterized by reduced lymph node radioactivity, together with increased kidney and/or urine radioactivity 24 hr after injection, in allogeneic hosts as compared with syngeneic recipients of the same cell suspension. ALC has a number of features in common with other natural resistance systems. Nevertheless, the administration of hydrocortisone or silica in doses comparable to those causing diminished NK activity in rats was without effect on ALC; likewise cyclophosphamide at a dose capable of significantly impairing NK activity in rats had, at most, a minor effect on ALC. Under the conditions of administration cyclosporin A was without effect. The interferon inducer polyinosinic polycytidilic acid (poly I:C) brought about a significant augmentation of ALC.