CELL-SURFACE MARKER ANALYSIS OF RAT THYMIC DENDRITIC CELLS

Rat thymic dendritic cells have been isolated by collagenase digestion , separation of the low-density cell fraction by centrifugation on met rizamide, and differential adherence. Tbe resulting dendritic cell pre paration had a purity of > 90%, and has been analysed by flow cytometr y (FCM) using a large panel of monoclonal antibodies (mAb). Dendritic cells expressed major histocompatibility (MHC) class I and class II mo lecules, the leucocyte common antigen CD45, the rat leucocyte antigen OX44, the rat macrophage marker ED1, and the adhesion molecules Mac-1, LFA-1 and ICAM-1. They were negative for the T- and B-cell-specific f orms of CD45, CD45R and B220, and the B-cell marker OX12. Concerning T -cell marker expression, they were negative for T-cell receptor (TcR) and OX40, but they expressed CD2, CD4 and CD8, and interestingly, 50% of DC were CD5+, 50% expressed the alpha-chain of interleukin-2 recept or (IL-2R), and 80% were positive for the T-cell activation antigen re cognized by the mAb OX48. Moreover, 60% of DC expressed high levels of Thy-1, whereas 40% displayed intermediate levels of this T-cell marke r.