SUBACUTE EXPOSURE TO 2,3,7,8-TETRACHLORODIBENZO-P-DIOXIN (TCDD) IN GERIATRIC MICE: EFFECTS IN THYMIC, SPLENIC, AND BONE MARROW HEMATOPOIETIC CELLS

Abstract

Exposure of geriatric m ice (21- 1 m o) to the environmental contaminant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) produced alterations in thymus, spleen, and bone m arrow hematopoietic cell populations. Female C57BL/ 6 mice were dosed (via intraperitoneal injection) with 0, 5.0, or 10.0 ug/ kg TCDD in corn oil for 5 consecutive days. Evaluation of imm une endpoints took place on the second day following cessation of dosing. A limited but significant reduction in bone marrow cellularity was produced by exposure to TCDD at 10.0 ug/ kg, in the presence of unaltered percentages of cells expressing CD45, CD45R, and Mac-1 antigens. A lim ited increase in splenic cellularity was also present at the higher dose level of TCDD, where trends toward reduced percent++ ages of CD45R B cells and Thy 1.2 T cells were observed but did not reach significance. Pronounced, dose-dependent thymic hypocellularity was evident at both levels of chemical exposure in the aged m ice, and was accom panied by+ + decreased percentage...