THE ENIGMATIC PLASMACYTOID T-CELLS DEVELOP INTO DENDRITIC CELLS WITH INTERLEUKIN (IL)-3 AND CD40-LIGAND

A subset of CD4(+)CD11c(-)CD3(-) blood cells was recently shown to dev elop into dendritic cells when cultured with monocyte conditioned medi um. Here, we demonstrate that CD4(+)CD11c(-)CD3(-) cells, isolated fro m tonsils, correspond to the so-called plasmacytoid T cells, an obscur e cell type that has long been observed by pathologists within seconda ry lymphoid tissues. They express CD45RA, but not markers specific for known lymphoid- or myeloid-derived cell types. They undergo rapid apo ptosis in culture, unless rescued by IL-3. Further addition of CD40-li gand results in their differentiation into dendritic cells that expres s low levels of myeloid antigens CD13 and CD33.