The HLA-DR antigen is constitutively expressed on professional antigen-presenting cells (dendritic cells, B cells, monocytes/macrophages), and its expression is further up-regulated upon activation. On T cells, NK cells, hematopoietic precursor cells, and some epithelial cells the expression of HLA-DR is induced by cell activation.
Downstream applications
HLA-DR–positive cells are isolated, for example, for serological typing of HLA class II molecules or studies on antigen presentation.