CD4 and tuberculosis: CD4+ T cells along with the cytokines IL-12, IFN-γ, and TNF-α play a pivotal role in the control of tuberculosis and leprae infections [10] Coinfection has been explained by the failure of host's T cells to respond to IL-12 in vivo and as a result host's T cells are unable to produce an appropriate Th 1 cell response [10].