Receptors for Helix pomatia A haemagglutinin (HP) on a subpopulation of human B cells

Abstract

Receptors for Helix pomatia A haemagglutinin (HP) have earlier been found on neuramidinase treated T-lymphocytes in human peripheral blood. In contrast, the majority of the B-lymphocytes, characterized by surface bound IgM and/or IgD(SIg)lack these receptors. Double marker experiments with fluorochrome labelled reagents have now shown that a minor fraction (3--24%) of the IgM/d bearing lymphocytes in normal human blood also have HP-receptors. These HP+ B-cells constitute approximately 1% of the HP+ lymphocytes in adult blood. Fractionation on HP-Sepharose columns showed that the HP+ B-cells are readily eluted with buffer containing 0.1 mg N-acetyl-D-galactosamine. In contrast, the majority of the HP+-SIg--cells require higher concentrations of the competing hapten for elution (1 mg D-Ga1NAc/ml buffer). This indicates that the HP-receptors on these B-cells differ qualitatively or quantitatively from those on the majority of the T-cells. Previous findings of HP-receptors on the SIg+ leukaemic cells in the blood of patients with chronic lymphocytic leukemia suggested that these structures are expressed on an immature variety of B-cells. This assumption is favoured by the present finding that approximately 80% of the lymphocytes with surface bound IgM/D in cord blood also have HP-receptors. Therefore, the HP-receptors seems to fall in the category of differentiation markers and constitutes a useful tool for characterization and separation of human lymphocytes within both the T- and the B-compartments.