Reappraisal of lymphocyte classification by means of surface morphology.

Prior scanning electron microscope studies have indicated that T (thymus derived) lymphocytes appear "smooth" while human B (thymus independent) lymphocytes appear "hairy" with numerous microvilli covering their surfaces. A recent report (24) has raised some doubt as to the validity of classifying lymphocyte subpopulations on this purely morphologic basis. We have examined lymphocytes taken from congenitally athymic "nude" mice (lacking T cells) and compared them with those taken from normal littermates and CBA/J mice (both having T cell populations). We have determined that there are no distinguishable differences between the distribution of surface morphologies of lymphocytes from animals either with or without T and B cells. Our studies indicate that the classification of T and B cells, based on cell surface features, requires more than just finding out whether or not the cells are smooth or hairy.