REDUCTION IN HLA-DR ANTIGEN DENSITY ON ALVEOLAR MACROPHAGES OF SMOKERS

The expression of HLA class II genes is essential to the antigen-presenting function of monocytes and macrophages. With a new cytofluorometric method of single-cell analysis we investigated the density of HLA-DR antigen expression on alveolar macrophages (AM) of smokers. Although all AM of nonsmokers (100 +/- 1%) expressed HLA-DR antigens, only 79 +/- 12% of AM from smokers showed positive findings (p < 0.001). Furthermore, the antigen density of those cells expressing this antigen was significantly reduced in smokers (p < 0.001). The defective expression of class II genes on AM of smokers might contribute to the impaired antigen-presenting function found by some previous investigators.