Antigenic differences between subsets of peripheral blood lymphocytes differing in their right angle light scatter in flow cytometric analysis.

The expression of various cell surface markers on peripheral blood lymphocytes (PBL) of young children and of adults was determined by flow cytometry among cells with either high or low light side scatter (SSC). In adults and in children, CD4+ lymphocytes (helper T cells) were more abundant among PBL with low SSC than among PBL with high SSC. The proportion of CD57+ (Leu-7+) cells (NK cells and a subset of CD8+ T cells) was significantly elevated among high SSC PBL, while that of CD8+ PBL (cytotoxic suppressor T cells) was only slightly elevated. CD4+ and CD8+ lymphocytes which coexpressed the CD29 marker, characteristic for activated or memory T cells, were significantly more abundant among lymphocytes with high SSC. In adults, the proportion of CD4+ CD45RA+ lymphocytes, naive T cells, was significantly higher among low SSC cells. The present study indicates that determination of the SSC of lymphocyte subsets by flow cytometry can improve the discrimination among lymphocyte subpopulations and contribute to assessment of their state of activation.