ACTIVE REPLICATION OF HIV-1 AT THE LYMPHOEPITHELIAL SURFACE OF THE TONSIL

Cells that are infected with HIV-1 were visualized at the mucosal surf ace of the nasopharyngeal and palatine tonsils in 14 specimens from pa tients with CD4(+) T-cell counts of 200 to 900/mu l and 2- to 10-year histories of HIV-1 infection. Most of the cells with intracellular HIV -1 protein were small but multinucleated. The majority of these syncyt ia could be double labeled for HIV-1 RNA and a dendritic cell marker S 100. In the palatine tonsil, the infected cells were not found in the stratified squamous epithelium that is adjacent to the pharynx. Instea d, the S100(+) infected syncytia were localized to the surface of tons il invaginations or crypts. This mucosa, termed lymphoepithelium, cont ains antigen-transporting M cells that lie above regions where S100(+) dendritic cells are juxtaposed with CD4(+) lymphocytes. Likewise, inf ected cells were found in lympho-epithelium and not respiratory epithe lium of nasopharyngeal tonsils or adenoids. We propose that lymphoepit helia, the histological term that describes the specialized regions wh ere antigens access mucosa-associated lymphoid tissue, are sites where HIV-1 replication can be enhanced in syncytia derived from dendritic cells.