SEQUESTRATION FROM IMMUNE CD4-CELLS OF MYCOBACTERIA GROWING IN HUMAN MACROPHAGES( T)

CD4+ helper T cells mediate resistance to tuberculosis, presumably by enhancing the antimicrobial activity of macrophages within which the M ycobacterium tuberculosis organism grows. A first step in resistance s hould be the presentation of mycobacterial antigens by macrophages to CD4+ T cells. However, when the antigenic stimulus is limited to organ isms growing in human monocytes, the organisms become sequestered from immune CD4+ T cells. This block in presentation is selective for grow ing mycobacteria and not for other stimuli. Sequestration would allow replicating organisms to persist in infected individuals and may contr ibute to virulence.