Concanavalin A responsiveness and interleukin 2 production in the snake Spalerosophis diadema

Thymocytes and splenocytes (SC) of adult snakes, Spalerosophis diadema, responded to concanavalin A (Con A) in vitro by strong proliferation during the spring and autumn seasons. Con A-mediated mitogenesis was, however, abrogated in summer and winter. Conditioned medium (CM) collected from snake SC cultures stimulated with Con A in spring or autumn could enhance the Con A summer and winter responses and support the proliferation of splenic lymphoblasts. Gel filtration of native CM on Sephadex G-100 revealed the presence of two biologically active peaks of molecular weight 39-42 and 15 KD. However, only one peak of activity corresponding to molecular weight (m.w.) of 14-15 KD was observed when CM was subjected to analysis by sodium dodecyl sulphate gel electrophoresis (SDS-PAGE). The active molecular forms exhibited isoelectric points of 5.5-5.8 and 6.4-6.6. The findings suggest that Con A activation of snake lymphocytes in optimal seasonal conditions is associated with the secretion of a lymphokine analogous to the interleukin 2 (IL 2) of endothermic vertebrates.