Peanut agglutinin. IV. A tool for studying human mononuclear cell differentiation.

Peanut agglutinin (PNA) has previously been shown to be a 'marker' for early T subpopulations in mice. We have investigated whether it could also be used in the study of human mononuclear cells. 50--60% of human thymocytes have binding sites for PNA. When separated on a discontinuous Ficoll gradient, the PNA-positive thymocytes are found preferentially in the layers corresponding to the immunoincompetent cells. In the peripheral blood only 5% of the mononuclear cells are PNA-positive and we have shown that these cells are monocytes. In tonsils 13% of PNA+ cells are found and they are mostly lymphocytes. Thus, PNA is a marker for some T cell subsets present in the thymus and tonsils.