Characterization of peanut agglutinin receptors of murine thymocytes

Abstract

Murine thymocytes can be separated on the basis of their agglutinability by peanut agglutinin (PNA) into two broad subpopulations assimilated to immunoincompetent agglutinated PNA + cells and immunocompetent nonagglutinated PNA − cells. Seven surface membrane components have been isolated by immunoprecipitation using rabbit anti-PNA IgG and Staphylococcus aureus bearing protein A, from PNA-coated radiolabeled immature cells. These components (apparent molecular weights of 180, 175, 130, 115, 65, 26, and 23 kDa) labeled by the galactose oxidase/ tritiated sodium borohydride method and by 125I-iodination are glycoproteins which are PNA-receptor sites normally exposed on the surface membrane of PNA + thymocytes. The nonagglutinated PNA − cells also possess on their surface unmasked receptors for the lectin (175–180 kDa) but in lower amounts. Neuraminidase treatment prior to galactose oxidase/tritiated sodium borohydride labeling shows that the majority of PNA receptors is present on the PNA − thymocyte surface but are masked by sialic acid residues on the terminal position of the oligosaccharidic chains.