Effect of 2,4-dicholorophenoxyacetic acid, trifluralin and triallate herbicides on immune function.

The commercial formulations of 3 commonly used herbicides (the amine salt of 2,4-dichlorophenoxyacetic acid, trifluralin and triallate) were evaluated for effects on immune function in male Fisher 344 rats. The herbicides were prepared in an olive oil vehicle and administered by oral gavage twice weekly for 28 d at the following doses: 10.0 mg 2,4-D/kg; 17.5 mg trifluralin/kg; 5.0 mg triallate/kg/treatment. Normal body weight and organ/body weight ratios indicated the rats tolerated the herbicide treatments without difficulty. Exposure to 2,4-D did not alter lymphocyte blastogenesis, 1 gm antibody production (anti-sheep red blood cell), lymphocyte cell surface marker expression or phagocytic function of peritoneal macrophages. Trifluralin acted as a weak mitogen, but impaired T-lymphocyte blastogenesis induced by phytohemagglutinin and concanavalin A. Other immunological measurements were unaffected by trifluralin exposure. Triallate exposure reduced peritoneal macrophage phagocytosis by 33%, showed weak mitogenic properties and impaired T-lymphocyte blastogenesis in the presence of phytohemagglutin. Triallate also increased the anti-sheep red blood cell response expressed/spleen by 43%, a phenomenon suggestive of a compensatory response to minimize the impact on overall immune function. The changes in lymphocyte or macrophage function due to the herbicide treatments were not associated with changes in lymphocyte cell surface antigen expression.