Identity of HML-1 Antigen on Intestinal Intraepithelial T Cells and of B-ly7 Antigen on Hairy Cell Leukaemia

Immunoprecipitation of radioiodinated hairy cell leukaemia (HCL) cell lysates with monoclonal antibody (MoAb) HML-1, originally reported to recognize intraepithelial T cells, and with MoAb B-ly7, originally reported to react with HCL, led to identical biochemical characteristics. In SDS-PAGE under reducing conditions, a major band of 143 kDa, a broad band ranging from 112 to 122 kDa, and two additional faint bands of 175 and 100 kDa could be determined. Deglycosylation of N-linked sugar moieties by treatment of immunoprecipitates with endoglycosidases indicated that the two main protein cores of the antigen are predominantly if not exclusively glycosylated by complex and hybrid types of oligosaccharide chains. Competitive binding inhibition demonstrated that both MoAb are directed against different epitopes. Immunohistochemically, the staining patterns obtained with both MoAb in normal tissues, in T- and B-cell lymphomas, and in HCL were identical except for a single case of HCL which was HML-1-/B-ly-7+. We conclude that MoAb HML-1 and B-ly7 recognize the same antigen.