A histological and immunocytochemical study of lymphoid tissue in rectal biopsies from homosexual men.

A histological study of the lymphoid tissue of the rectums of 323 homosexual and 30 heterosexual men (including five intravenous drug users seropositive for human immunodeficiency virus, HIV) was undertaken. Marked lymphoid hyperplasia (germinal centre greater than 680 microns in diameter) was found in 13 men, nine of whom had a sexually transmitted infection of the rectum. Immunocytochemical studies showed that the germinal centres contained B-cells and follicular dendritic cells, surrounded by CD4+ and CD8+ T-cells in a ratio of between 5:1 and 10:1. In HIV-infected men there were decreased numbers of CD4+ cells and increased numbers of CD8+ cells, resulting in a ratio of between 0.8:1 and 2:1. In biopsies from four of seven HIV-infected men the follicular dendritic cell processes appeared shorter and fragmented. The pathogenesis of HIV infection is discussed in the light of these findings.