SUPPRESSION OF B-CELL MEDIATED IMMUNITY IN JUVENILE CHINOOK SALMON (ONCORHYNCHUS-TSHAWYTSCHA) AFTER EXPOSURE TO EITHER A POLYCYCLIC AROMATIC HYDROCARBON OR TO POLYCHLORINATED-BIPHENYLS

Juvenile chinook salmon (Oncorhynchus tshawytscha) were injected intraperitoneally with either the polycyclic aromatic hydrocarbon, 7,12-dimethylbenz[a]anthracene (DMBA)(1) or with the commercial polychlorinated biphenyl (PCB) mixture, Aroclor 1254, to assess effects on the B-cell mediated immune response. B-cell mediated immunity was assessed by examination of the primary and secondary plaque-forming cell (PFC) responses of anterior kidney and splenic leukocytes to a T-independent antigen, trinitrophenyl-lipopolysaccharide (TNP-LPS) and to a T-dependent antigen, TNP-keyhole limpet hemocyanin (TNP-KLH). Salmon exposed to DMBA at dosages of 20% or 1% of the 96 hr LD(50) (12.7 mg and 0.6 mg/kg of salmon, respectively) or to PCBs at a dosage of 20% of the 96 hr LD(50) (54.0 mg/kg of salmon) exhibited a suppressed PFC response. The secondary PFC response of anterior kidney and splenic leukocytes to both antigens and the primary splenic PFC response to TNP-LPS were suppressed in salmon exposed to either DMBA or PCBs. However, only the primary PFC response of anterior kidney leukocytes to TNP-LPS was suppressed in salmon exposed to PCBs and no suppression of this response was observed in salmon exposed to DMBA. Neither anterior kidney or splenic leukocytes from salmon exposed to DMBA or PCBs showed an altered primary PFC response to the T-dependent antigen, TNP-KLH. These results suggest that B-cell mediated immunity in salmon is suppressed by known mammalian immunosuppressants and that suppression of the PFC response observed previously in salmon from an urban estuary may be due to contaminant exposure.