T lymphocyte subsets in Mediterranean spotted fever.

Several studies have previously suggested the possible role of a T lymphocyte suppressor population in infections by species of the genus Rickettsia. In 15 patients with Mediterranean spotted fever (MSF), we quantified, during the acute and convalescent phases of the disease, the peripheral blood lymphocyte populations using monoclonal antibodies that recognize CD3+, CD4+, CD8+, CD38+ and CD20+ cells. In three cases a reversal in the normal ratio of T lymphocyte helper-inducer/suppressor-cytotoxic subsets was detected lasting, in two of them, up to the fifth week of the disease. This disturbance was always weak and lacked clinical significance.