Morphology and Kinetics of Lymphocytes

Abstract

On the basis of size it is a common practice to classify lymphocytes as large, medium and small without drawing distinct boundaries between the three groups. We can now say with assurance that the developmental sequence is large → medium → small, and it is, of course, now well known that the small lymphocyte, a non-DNA synthesizing cell, can be stimulated to enlarge and divide, producing progeny which carry out a variety of immunological roles. Whether or not small lymphocytes can serve as precursors to cells other than ones of the lymphoid series remains controversial. Our investigations have provided no evidence in support of the view that the small lymphocyte is a multipotential stem cell. In this context, the view that the transitional cell of bone marrow (Fig. 1) is an intermediate stage between the small lymphocyte and blast cell is no longer acceptable. Studies in our laboratory (22, 36) and those of Yoshida and Osmond (45) have, in fact, shown that transitional cells of bone marrow give rise to small lymphocytes.