A new method for the separation of cell subpopulations using a lectin as a reversible probe, is described. We have found that the major immature thymocyte subpopulation can be readily separated from the immunocompetent minor subpopulation by agglutination with peanut agglutinin (PNA) and can be recovered as viable single cells by dissociation of the agglutinated cells with d-galactose. The two subpopulations were characterized by their content of H-2 and θ antigens, their graft versus host activity and their mitogenic response to phytohemagglutinin and concanavalin A. Binding studies with [125I]PNA indicate that attachment of sialic acid residues to the PNA receptor may be an important step in the maturation of the murine thymocytes.

Separation of mouse thymocytes into two subpopulations by the use of peanut agglutinin