Alteration of thymic cell subsets by cocaine administration and murine retrovirus infection in protein undernourished mice

Retrovirus infection, cocaine administration, and nutritional deficiencies are known to individually produce impairment of the immune system. Therefore, we developed a murine model to study the effect of daily cocaine administration, protein malnutrition, and retrovirus infection causing murine AIDS on the lymphoid cell populations of the thymus. C57BL/6 female mice fed a diet containing 4% protein were studied following chronic cocaine administration and LP-BM5 murine leukemia virus (MuLV) infection. Cocaine administration reduced body and thymus weight. Cocaine partially prevented thymus enlargement due to lymphoid cell proliferation induced by murine retrovirus infection. Cocaine treatment affected dramatically the thymus of protein-malnourished mice where the absolute number of Thy 1.2⁺, CD4⁺ and CD8⁺ cells represented only 10% of the control values. Daily saline injection also induced a significant decrease in the number of Thy 1.2⁺, CD4⁺ and CD8⁺ cells per thymus. These results suggest that the thymus glands of mice fed a low protein diet were susceptible to stress. Retrovirus infection provoked a decrease in the percentage and absolute number of Thy 1.2⁺, CD4⁺ and CD8⁺ cells in the thymus. This effect was potentiated by cocaine treatment. Therefore, cocaine was able to potentiate the impairment of the immune system caused by MuLV infection. We consider that cocaine could alter the immune system by altering the expression of T cell differentiation markers after direct interaction with thymocytes or through the neuroendocrine-thymus axis. Moreover, this effect was more dramatic and severe during protein malnutrition.