Based on in vitro and ex vivo clinical findings some of the potential pathways by which HIV-1 induced CCL2 can contribute to TB reactivation and associated pathology (Figure 1) include (1) HIV-1 infected alveolar macrophages secreted CCL2 recruits CCR2+ leukocytes including macrophages, CD4+ T cells, and NK cells to participate in immune reactions. The gene discussed is CD4; the disease is tuberculosis.