Effects of thiobenzamide on the rat immune system.

Thiobenzamide (TB) is a thiono-containing compound endowed with liver-damaging properties and promoting ability on liver carcinogenesis. When administered in a single dose to normal as well as to adrenalectomized rats, this compound induced a striking thymus cortex involution without relevant effects on the morphological features of other lymphoid organs such as spleen and lymph nodes. The proximal TB metabolite TB-S-oxide (TBSO) shared these effects with the parent compound, whereas the terminal metabolite benzamide (BA) was ineffective. The effect of TB on thymus was found to be dose- and age-dependent. Furthermore, acute TB treatment 12h before priming with the T-dependent antigen sheep erythrocytes impaired the secondary antibody response. In addition, TB administration affected not only cell-mediated immunity (as evidenced by a decreased delayed hypersensitivity response) but also mitogen-induced proliferation of blood lymphocytes. On the contrary, the chemotactic response of polymorphonuclear leukocytes obtained from TB-treated rats was unchanged.