CD4 and sarcoidosis: The causes and drivers of sarcoidosis remain unclear, and numerous factors have been implicated, including infection, dust, antigen-presenting cells, CD4+ T cells, cytokines such as interleukin-2 and tumor necrosis factor-A, as well aspolymorphisms in genes encoding human leukocyte antigen and butyrophilin-like protein 2 (3).