Interaction of peanut agglutinin with normal human lymphocytes and with leukemic cells.

The interaction of peanut agglutinin (PNA) with human thymocytes, peripheral blood lymphocytes, and peripheral blood cells of various types of leukemia was investigated by using fluorescein isothiocyanate-conjugated PNA. The majority of human thymocytes (60-80%) bind the lectin. The major subpopulation of thymocytes that is PNA-positive was separated from the PNA-negative cells by differential agglutination with the lectin. The two thymocyte subpopulations were tested in the mixed lymphocyte reaction and with the phytohemagglutinin of Phaseolus vulgaris. The poor response of the PNA-positive thymocytes to these stimuli indicates that these thymocytes are functionally immature. The fluorescein isothiocyanate-PNA-binding test with peripheral blood lymphocytes of leukemic patients revealed that in most acute leukemias the PNA receptor is exposed on the blastic cells, whereas in most cases of chronic leukemia the peripheral blood lymphocytes are PNA-negative. The validity of PNA as a marker of immature blood cells and its potential clinical application are discussed.