Effects of cocaine administration to influenza virus-immunized mice on cytokine profiles of individual splenic CD4+ and CD8+ T cells.

We have analysed the effects of cocaine, administered to mice during the in vivo differentiation of effector T cells stimulated by antigen (influenza virus) recognition, on the frequency of IL-2-, IL-4- and interferon-gamma (IFN-gamma)-expressing CD4+ and CD8+ T cells. Each animal was injected intraperitoneally with 10 mg/kg of cocaine 6, 24, 48 and 72 h after immunization with A/PR8 influenza virus (PR8). This enabled the determination of the pharmacological effects of cocaine on T cells during the initial step of the immune response, which is characterized by the production of large amounts of immunoregulatory cytokines. The distribution of IL-2-, IL-4- and IFN-gamma-producing CD4+ and CD8+ T cells was assayed on unseparated PR8-immune spleen cells, obtained from mice treated with cocaine or vehicle, and restimulated in vitro with UV-inactivated PR8 virus. The frequency of T cells singly or co-expressing the above three cytokines was determined at single-cell level by simultaneous flow cytometric analysis of intracellular cytokines and surface antigen expression. In parallel, the levels of IL-2, IL-4 and IFN-gamma in the culture supernatants were quantified by ELISA. The results showed that cocaine, administered during the in vivo virus-induced differentiation of T cells, caused an increase of both the frequencies of CD8+ T cells singly and co-expressing IL-2 and IFN-gamma and the levels of these cytokines in virus-restimulated spleen cell culture supernatants, compared with those of untreated controls. In contrast, no effect was found on IL-4-positive CD8+ T cells and on IL-2-, IFN-gamma- and IL-4-positive CD4+ T cells. Our findings suggest that the immunomodulatory effects of cocaine may be due to the up-regulation of the production of IL-2 and IFN-gamma by CD8+ T cells with a type 0 cytokine profile.