PCB CONGENERS AND THE MURINE IMMUNE-SYSTEM - THE CAPACITY OF ISOLATEDCONGENERS TO DECREASE SPLEEN SPECIFIC ANTIBODY-FORMING CELL NUMBERS VARIES WITH THE TOXIC EQUIVALENCE FACTORS OF THE CONGENERS

Polychlorinated biphenyl (PCB) congeners 77 (3,3',4,4'-tetrachlorinate d biphenyl) and 118 (2,3',4,4',5-pentachlorinated biphenyl) were given by gavage as a single dose to female C57BL/6J mice. The dose levels t ested were 25 and 100 mu mol/kg body weight for PCB-77, and 250 and 80 0 mu mol/kg for PCB-118. 2 days after dosing, the mice were either imm unized with sheep red blood cells (SRBC) or they were killed and their livers were removed for determination of ethoxyresorufin-O-deethylase (EROD) activity, and their spleens were removed for assays of natural killer (NK) cells and mitogen stimulation assays. The immunized mice were killed 4 days after immunization, and their spleens were removed for determination of the number of plaque forming cells. Both congener s induced a reduction in anti-SRBC forming cells and an increase in li ver microsomal EROD activity, their relative potencies being of the sa me order of magnitude as reported for their general toxicity. No effec t was observed on NK cell activity or on the response to mitogens in v itro.