HIV-negative patients without predisposing lung disease who develop pulmonary MAC have increased numbers of CD4 and CD8 T cells as well as higher levels of TNF-α, IL-1β, IL-6, and IL-8 in bronchoalveloar fluid (BAL), suggesting the possibility that both CD4 and CD8 T cells contribute to MAC immunity (37). This evidence concerns the gene CD4 and lung disorder.