T follicular helper cells
T follicular helper cells (Tfh) are a specialized subset of CD4+ T cells that were first identified in the human tonsil. They play a critical role in protective immunity helping B cells produce antibody against foreign pathogens. Tfh are located in secondary lymphoid organs (SLOs), including the tonsil, spleen and lymph nodes. These organs contain numerous lymphocytes, separated into defined T and B cell zones.