TYPE-III BARE LYMPHOCYTE SYNDROME - LACK OF HLA CLASS-II GENE-EXPRESSION AND REDUCTION IN HLA CLASS-I GENE-EXPRESSION

The bare lymphocyte syndrome (BLS) consists of an association between a combined immunodeficiency disease and a significantly reduced expres sion of either human histocompatibility leukocyte antigens (HLA) class I (HLA-A, -B, -C) or HLA class II (HLA-DP, -DQ, -DR) at the cell surf ace. BLS type III, the more frequent form of this syndrome, is charact erized by impaired expression of both class I and class II antigens on patients' cells, in particular on leukocytes. We describe herein the demonstration that expression of HLA class I molecules was reduced by approximately half on Epstein-Barr virus-transformed B cells (LCL) der ived from type III BLS patients. HLA class I mRNA level was also decre ased to the same extent. Expression of HLA class I molecules was also very significantly reduced at the surface of these fibroblasts as was mRNA specific for HLA class I Simultaneously, the expression of HLA-DR molecules on LCL was even more greatly decreased, and the expression of HLA-DQ antigens was virtually abolished. Molecular analysis demonst rated an absence of mRNA far the alpha- and beta-chains of HLA-DQ and HLA-DR in the patients' lymphocytes. In general, such patients present with an association of an absence of expression of HLA class II antig ens and a significantly reduced expression of HLA class I antigens, Th e mechanism of this association is still uncertain.