A SUBSET OF HLA-DR9 MOLECULES IS DETECTED BY A POLYMORPHIC MONOCLONAL-ANTIBODY ON LYMPHOBLASTOID CELL-LINES BUT NOT ON PERIPHERAL-BLOOD LYMPHOCYTES

Some mAbs recognizing polymorphic epitopes of HLA-DR molecules exhibit striking differences of reactivity with the same HLA-DR molecules exp ressed by different cell types. In this study, we investigated the bas is for the differential reactivity of the polymorphic anti-DR mAb OHA TM901 with HLA-DR9 molecules expressed by human PBLs or LCLs. By immun oprecipitation experiments we showed that OHA TM901 recognizes a subse t of HLA-DR9 molecules from LCLs. This subset corresponds to HLA-DR9 m olecules containing immature-type oligosaccharides. The absence of OHA TM901 reactivity with HLA-DR9 PBLs, as revealed by cytofluorometry an alysis, suggests that this subset is either not expressed or expressed at a very low level on PBLs. These results indicate thar overexpressi on of HLA-DR molecules in immortalized LCLs could lead to cell-surface expression of underglycosylated forms which are generally not found o n the cell surface of PBLs.