In vitro stimulation by mitogens of peripheral blood lymphocytes from rainbow trout (Salmo gairdneri).

Peripheral blood lymphocytes of the rainbow trout can be stimulated by PHA, conA and LPS. Optimal concentrations for stimulation are 1-50 microgram/ml for PHA, 1-10 microgram/ml for ConA and 1 microgram/ml for LPS. Best stimulation is obtained after an incubation period of 72 h at a temperature of 28 degrees C. Thymidine incorporation into lymphocytes is enhanced when PHA and LPS (1 microgram/ml each) are given simultaneously. After a first stimulation by LPS the lymphocytes become less sensitive to a second exposure to this same mitogen. In contrast, LPS-primed lymphocytes are highly reactive to PHA. These results suggest that there exists (at least) two populations of peripheral blood lymphocytes, one sensitive to PHA and the other sensitive to LPS.