Cryptococcal-related meningoencephalitis in a patient with sarcoidosis and CD4 lymphocytopenia: thorough immunological characterization of lymphocyte homeostasis.

Cryptococcal meningoencephalitis is the most common infective complication observed in patients with CD4 lymphocytopenia, including sarcoidosis. T-cell immunity is well characterized in HIV-related infections and data regarding immunity in cryptococcosis animal models is now available; on the contrary, little is known about the immune status in non-HIV-related infections. We report on reduced production of new T cells observed in a patient with sarcoidosis, CD4 lymphocytopenia, and cryptococcal-related meningoencephalitis. Although T cells presented with an intact proliferative capacity, they were oligoclonally expanded showing an effector memory phenotype. However, the deleterious activity of effector memory cells could have been controlled by the expansion of the regulatory T cell subset with the highest suppressive capability. This information provides a better understanding of the immune response to Cryptococcus occurring in non-HIV-associated cases, the predisposition to infection, and the role of different cell subtypes in controlling the disease in humans.