BENZO[A]PYRENE-INDUCED ALTERATIONS IN TOTAL IMMUNE CELL NUMBER AND CELL-SURFACE ANTIGEN EXPRESSION IN THE THYMUS, SPLEEN AND BONE-MARROW OFB6C3F1 MICE

Although considerable evidence suggests that carcinogenic polycyclic a romatic hydrocarbons are Immunosuppressive compounds, limited informat ion is available regarding precise effects of these agents on cells in bone marrow, thymus and spleen of B6C3F1 mice war investigated. B[a]P treatment was found to reduce thymic cellularity and also to signific antly alter normal thymocyte differentiation, as indicated by expressi on of CD4 and CD8 cell-surface antigens. Exposure to B[a]P also reduce d cellularity of the bone marrow, including decreased percentage and a bsolute number of CD45R(+) B-lineage lymphocytes. Further, B[a]P treat ment dramatical ly increased the percentage of CD44(hi) cells in bone marrow, while proportionately reducing CD44(lo) cells. These results m ay Indicate cD44(lo) bone marrow cells, including prolymphocytic cells , represent sensitive targets of B[a]P. The spleens of treated mice we re found deficient In both Thy 1.2(+) T lymphocytes and CD45R(+) B lym phocytes, effects that correlate well with the chemical-induced altera tions observed in thymus and bone marrow, respectively.