COMPARATIVE EXPRESSION OF MAJOR HISTOCOMPATIBILITY COMPLEX (MHC) ANTIGENS ON CD5(-) B-CELLS IN PATIENTS WITH CHRONIC LYMPHOCYTIC-LEUKEMIA (CLL)() AND CD5()

The aim of this study was to investigate the expression of major histo compatibility complex (MHC) antigens on CD5(+) and CD5(-) B cells of 1 3 patients with chronic lymphocytic leukaemia (CLL). This was carried out using a series of monoclonal antibodies (MAbs) against polymorphic and monomorphic class I and class II antigens, as well as to the tran sferrin receptor and assessed by flow cytometry and direst and indirec t immunofluorescence. The expression of these molecules was assessed a s mean fluorescent intensity (MFI). The results showed that cells from all 13 individuals expressed monomorphic class I antigens. The number of cases expressing polymorphic HLA-Bw6, -Bw4, -B7, -B27 and -A2 clas s I antigens on CD5(-) B cells was 11 (85%), 6(46%), 2(15%), 1(8%), 3 (23%), respectively, which was consistent with the expected population frequency distributions of these antigens. For each of the class I an tigens on CD5(+) and CD5(-) B cells, the ratio of the MFI was greater than 1 in 12 of 13 cases. For the transferrin receptor (CD71), this ra tio was also almost always greater than 1. These results indicate that , unlike solid tumours where the loss or abnormal expression of class I and II antigens is a frequent event, the expression of class I antig ens in CLL patients seems to be normal. This indicates that the loss o f these antigens cannot provide the leukaemic cells with a selective a dvantage to escape immunological detection. (C) 1998 Elsevier Science Ltd. All rights reserved.