HUMAN HOST RESPONSE TO MYCOBACTERIUM-TUBERCULOSIS

Despite the importance of tuberculosis as the leading cause of death d ue to infectious disease in the world, it has only been recently that an understanding of the human host response in this infection has begu n to emerge. The key components of this response are cytokines and com ponents of cellular immunity, predominantly T-lymphocytes and macropha ges. Though the relationships among the components of the immune respo nse are complex, it seems likely that in response to mycobacterial inf ection associated with active disease, cytokines such as TNF-alpha and IL-1 beta are produced; these cytokines serve to recruit more lymphoc ytes, generally of the T-H (T helper) phenotype, which then produces s ubstances such as the macrophage activating factor interferon-gamma. M acrophages activated by IFN-gamma are thus stimulating to enhance intr acellular killing of mycobacteria. The role of other cytokines, such a s IL-6 and IL-8, both of which are induced by M. tuberculosis or its c ell wall components, is less clear. Further elucidation of the human h ost response to tuberculosis should help in the development of new vac cines and treatment strategies.