Modification of HLA expression on peripheral lymphocytes and monocytes during ageing

Immunosenescence involves modifications of humoral and cellular immunity. H ere we report the analysis of human leukocyte antigen (HLA) expression on T lymphocytes, B lymphocytes and monocytes of 58 healthy subjects aged 23-95 years old. Using a double staining immunofluorescence and flow cytometry a nalysis, we have determined the percentages of cells expressing HLA class-I and HLA-DR antigens. The number of antigenic sites expressed per cell were evaluated for HLA-ABCw, HLA-A, HLA-B, HLA-DR locus with a flow cytometry q uantification technique. With advancing age, we observed: (i) a significant decrease of the percentage of T cells and B cells expressing HLA-A product s; (ii) a decrease of the number of HLA class-I antigenic sites expressed p er cell on the three populations tested, predominantly on B cells and in a locus-dependent fashion; (iii) a decrease of the number of HLA-DR molecules expressed per T cell, although the percentage of T cells expressing DR pro ducts was increased; (iv) a significant diminution of the percentage of B c ells expressing HLA-DR molecules, without changes of the number of HLA-DR a ntigenic sites per cells. These changes in HLA expression with increasing a ge could contribute to the decreased level of immunologic responsiveness ob served with ageing and contribute to the modification of antigen recognitio n. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.