Density Distribution Analysis of Lymphocyte Populations

Abstract

DESPITE their suspected heterogeneity in origin, life span and precise function, lymphocytes are usually considered to be a single group because of the rather negative morphological criteria available. One morphological division of lymphocytes into immature (large and medium) and mature (small) cells is physiologically relevant, because the larger cells represent a population which synthesizes DNA and which divides, while the smaller cells are not usually engaged in DNA synthesis. Morphological criteria are as yet, however, inadequate to make possible identification of the classes of lymphocytes which are now studied by such functional tests as the ability to respond to antigen and to produce a colony of cells which form antibody, the ability to produce various classes of antibody or the ability to initiate a graft-versus-host reaction. This communication suggests equilibrium density gradient centrifugation as a technique which may prove valuable, not only in defining lymphocyte classes, but also in separating them from each other.