PRESENTATION OF MYCOBACTERIAL ANTIGENS BY HUMAN DENDRITIC CELLS - LACK OF TRANSFER FROM INFECTED MACROPHAGES

When exposed to a challenge of 10 Mycobacterium bovis BCG cells per an tigen-presenting cell, most human monocytes engulf several organisms. In contrast, blood dendritic cells which are potent antigen-presenting cells for several antigens are not detectably phagocytic for mycobact eria. We investigated the possibility that infected macrophages might regurgitate antigens for presentation by populations of human blood de ndritic cells. Macrophages were infected with M. bovis BCG, mixed with uninfected dendritic cells, and added to immune T cells, either bulk T cells or cloned populations from BCG vaccinees or patients recoverin g from tuberculosis. The macrophages were from donors who were mismatc hed to the T cells so that transfer of antigen to major histocompatibi lity complex-matched dendritic cells could be evaluated. As we describ e, there was no evidence for the transfer of mycobacterial antigens fr om macrophages to dendritic cells in a form that was stimulatory for t he T cells.