OUABAIN EFFECTS ON ACTIVATED LYMPHOCYTES - AUGMENTATION OF CD25 EXPRESSION ON TPA-STIMULATED CELLS AND OF CD69 ON PHA-STIMULATED AND TPA-STIMULATED CELLS

Ouabain (OUA) was capable of inhibiting peripheral blood lymphocyte (P BL) proliferation induced by phytohaemagglutinin (PHA) or phorbol este r (TPA), as measured by thymidine incorporation or cell cycle analysis . In this latter case it was possible to detect a block in the progres sion fi om G1 to S phase. This inhibition could not be reversed by int erleukin (IL)-2 and was not due to an effect on CD25 expression, as th is molecule was only reduced in PHA cultures treated with OUA. Convers ely, cultures activated by TPA and OUA showed an increased expression of CD25. The activation antigen CD69 was increased in both situations, suggesting that despite the absence of proliferative response the cel ls were being activated. The possibility that these cells were being d eviated to the activation pathway leading to apoptosis is now under in vestigation. This study also suggested that CD25 induction may occur v ia different pathways, and that the selective effect of OUA for PHA-ac rivated cells may become a useful tool for the understanding of the pr ocess. (C) 1997 International Society for Immunopharmacology.