Cytofluorographic Analysis of Pokeweed Mitogen‐stimulated Human Peripheral Blood Cells in Culture

Abstract

By use of monoclonal antibodies and flow cytometry techniques, peripheral blood mononuclear cells from young (20-30 years) and elderly (70+ years) subjects were analyzed before and after culture with pokeweed mitogen to gain insight into the cellular interactions responsible for the decreased B cell response observed in culture samples from the elderly. Data analysis of surface immunoglobulin-positive cells demonstrated no difference in the percentage of B cells in the elderly, while both plaque-forming cell and intracytoplasmic immunoglobulin assays showed significantly reduced B cell maturation (P = less than 0.01) compared with young controls. The B cell defect was shown to be functional and not a result of failure to proliferate and survive during incubation. Surface marker analysis of T cell subpopulations demonstrated a definite shift (P = less than 0.01) in the helper/suppressor T cell ratio in cultured samples from the elderly group (3.9) compared with young subjects (1.2). In addition to the absolute increase in the helper T cell population, forward-angle light scatter analysis demonstrated that, compared with young controls, a greater portion of the helper T cell population in the elderly subjects had characteristics of activated, blast-sized cells. The data reported in this study suggest that in the elderly group there is a functional immunoregulatory imbalance in the helper T cell subset.