Dioxin (2,3,7,8-tetrachlorodibenzo- p-dioxin) increases blood and spleen natural killer cell activity in the mouse

Abstract

The effects of 2,3,7,8-tetrachlorodibenzo- p-dioxin (TCDD) on immune function were studied in male A/J-mice after a loading dose of 5 μg TCDD/kg body weight (b.w.) followed by three weekly maintenance doses of 1.42μg TCDD/kg b.w. administered i.p. Tissue samples were prepared on days 28 and 120 after the first injection of TCDD. Classical histological signs of liver damage and lipid accumulation, as well as thymic atrophy were observed. Natural killer (NK) cell activity increased 3.4-fold and 2.2-fold in the blood and spleen, respectively, after 28 days, and these effects persisted on day 120. The increased NK-cell activity was concomitant with a decreased spleen T-lymphocyte activity after both 28 (65%) and 120 days (58%). However, the activity of spleen B cells seemed unaffected. We have shown for the first time that TCDD induces an increased activity of NK cells simultaneously in the blood and spleen, possibly as a response to a disturbed function of other immune cells.