Changes in intracellular cytokine levels in lymphocytes induced by measles virus

We investigated the changes in intracellular cytokine levels in different lymphocyte populations induced by measles virus (MV). MV-infected and uninfected peripheral blood mononuclear cells were cultured with phorbol 2-myristate 13-acetate plus ionomycin in the presence of monensin for 10 hr. Surface antigen and intracellular cytokines, interleukin (IL)-2, interferon (IFN)-gamma, and IL-4, were stained simultaneously and analyzed by flow cytometry. The percentage of cells that expressed IL-2 and IFN-gamma was significantly increased in MV-infected CD3+, CD4+, and CD8+ lymphocytes and alphabeta T lymphocytes compared with that in uninfected lymphocytes. In gammadelta T lymphocytes, expression of IFN-gamma, not IL-2, was increased in MV-infected cells compared with that in uninfected cells. IL-2 was increased mainly in MV-infected CD4+ lymphocytes and alphabeta T lymphocytes, whereas IFN-gamma was increased mainly in MV-infected CD8+ lymphocytes and gammadelta T lymphocytes. Expression of IL-4 was unaffected by MV infection. These results demonstrate that MV enhances intracellular levels of type 1 cytokines during the acute phase of measles.