To investigate the effects of Benzo[a]pyrene (B[a]P) and polychlorinated biphenyls (PCB) on in vitro cytokine production, we isolated cervical lymph node cells from ovalbumin (OA)-primed mice and the lymph node cells were cultured with various concentrations of B[a]P or PCB in the presence of antigen presenting cells (APC) and OA. B[a]P significantly increased the levels of interleukin-4 (IL-4) and -6(IL-6) in the culture supernatants. However, the levels of interferon-gamma (IFN-gamma) were decreased by treatment with PCB. These findings indicate that in vitro treatment with B[a]P or PCB modulate cytokine production from lymph node cells. (C) 1997 Elsevier Science Ltd.