Modulation of immunocompetent cell populations by benzo[a]pyrene.

These studies examined the cellular targets of benzo[a]pyrene (BaP)-induced immunomodulation. The immunocompetence of murine mononuclear leukocytes was evaluated following in vivo exposure to BaP. In vitro cell separation and reconstitution techniques were used to evaluate T-dependent antibody (TDAb) production and delineate the immunomodulatory events. Reconstitution of cultures using combinations of adherent and nonadherent cell populations from BaP- and vehicle-treated mice demonstrated that both of these populations were sensitive to the immunomodulatory effects of BaP. Examination of the adherent cell population demonstrated that low numbers of BaP-exposed accessory cells enhanced in vitro TDAb responses. These responses were greater than those observed for analogous cultures containing vehicle-exposed accessory cells. Recombination of separated B cells and T cells from vehicle- or BaP-treated mice in cultures containing normal adherent cells demonstrated that both B cells and T cells were sensitive to the effects of BaP. Cultures containing BaP-exposed cell populations were incapable of supporting control level antibody responses. The results indicate that in vivo BaP exposure induces immunomodulation through effects on macrophages, B cells, and T cells.