The role of the gut-associated lymphoid tissue in the pathogenesis of the acquired immunodeficiency syndrome (HIV-infection)

Abstract

Intestinal lamina propria T cells (LP-T) may be an important site of primary infection and replication of HIV. We studied the presence of HIV-infected cells and changes in lymphocyte subpopulations in the mucosa of HIV-infected patients by immunohistology. HIV-infected mononuclear cells were present in the intestinal lamina propria in 40% of HIV-infected patients. There was an increase in CD3+ and in CD8+ cells with a significant decrease of the CD4/CD8 ratio in the mucosa. The number of activated LP-T expressing IL-2 receptors (IL-2R) in the mucosa was decreased, whereas the percentage of HML-1+, Leu8+, Ki67+, and EBM11+ cells was not different in HIV-infected patients compared to controls. In addition, we investigated small intestinal structure and function in HIV-infected patients by three-dimensional morphometry and enzyme histochemistry. HIV-infected patients without additional intestinal infection had a lower villus surface area and a lower number of mitotic figures per crypt, the findings being most pronounced in patients with mucosal HIV-infected mononuclear cells. Brush border lactase/ß-glucosidase was significantly decreased or even absent in HIV-infected patients. These findings indicate a low grade small bowel atrophy and a maturational defect of enterocytes in HIV-infection which may also be caused by a loss of activated regulatory T cells in the mucosa of HIV-infected patients.