Suppression of humoral immunity in inbred mice by dieldrin

The effect of single, sublethal i.p. injection of dieldrin on the primary antibody response to thymodependent (sheep red blood cells, SRBC) and T-cell-independent (lipopolysaccharide, LPS) antigens were investigated in inbred C57Bl/6 mice. Time-course studies showed significant suppression of the anti-SRBC IgM and anti-LPS IgM response at 7-24 days and at 4-14 days, respectively, after exposure to 0.6 LD50 of dieldrin. The anti-SRBC IgG response was also suppressed by dieldrin exposure, however, maximal suppressory effect was found at 48 days after the pesticide exposure. Similar patterns of the dieldrin-induced suppression of the primary IgM response to the thymodependent and T-cell-independent antigens, in addition to the overall control of cytotoxicity of lymphoid cell populations, suggest rather dysfunction of cellular cooperation during the inductory phase of the immune humoral response.