Modulation of lymphocyte subsets in Peyer's patches of mice treated with monoclonal antibody against helper T-cells.

Treatment of mice with anti-L3T4, a monoclonal antibody directed against helper T-cells, impairs clearance of intestinal Giardia muris infection. The present study examined the effect of anti-L3T4 treatment on mouse Peyer's patch cytoarchitecture and on the distribution of T-cell subsets within microenvironments of the follicle. Female BALB/c mice, aged 8 weeks, were given 4-7 weekly injections of either anti-L3T4 (1 mg/wk) or PBS (control group), and Peyer's patches were examined by immunohistochemistry or flow cytometry. In anti-L3T4-treated mice, Peyer's patch follicles (B-cell areas) were about two thirds the size of follicles in controls, and virtually all the size difference occurred in germinal centers. Peyer's patches were depleted of L3T4+ cells, yet the proportion of Thy-1.2+ (all T) cells was not decreased correspondingly, and the distribution of Thy-1.2+ cells in the patches was similar to that in control mice. In anti-L3T4-treated mice, Thy-1.2+ cells consisted of (a) Ly-2+ (cytotoxic/suppressor T) cells, and (b) a population of Thy-1.2+ cells that were neither L3T4+ nor Ly-2+. After treatment, Ly-2+ cells accounted for most of the T-cells in interfollicular areas and were also scattered in follicles, in germinal centers, and below the dome epithelium--in areas where L3T4+ cells predominated in control mice. Thy-1.2+ cells that were L3T4- and Ly-2- were mainly localized below the dome epithelium. These shifts indicate complex interrelationships among different lymphocyte subsets in Peyer's patches.