Differential effect of aging on membrane immunoglobulin (mIg)-mediated endocytosis in the inductive and effector sites of the mucosal immune system.

The effect of aging on the endocytosis of anti-immunoglobulin (Ig) antibody as ligand by membrane Ig receptors (mIg) of B cells in the spleen, the mesenteric lymph nodes (MLN), and the Peyer's patches (PP) was investigated. Horse radish peroxidase (HRP) labelled (Fab')2 anti-mouse Ig specific for IgM, IgG, and IgA was used as the ligand. The rate of mIg mediated ligand endocytosis by aged B cells was significantly reduced in the PP as compared to the young group. In contrast, there were no age-related differences in the rate of mIg-mediated ligand endocytosis by B cells in the spleen and MLN. After 2 hr of incubation, about 70-80% of ligand added was internalized by splenic and MLN B cells from both young and old mice. Aged PP B cells showed significantly slower rate of ligand internalization as compared to those cells from young mice. This effect was pronounced at 30 and 60 min after incubation. Young PP B cells were found to internalize about 50% of the ligand within 30 min, while it took 60 min for aged B cells to internalize the same amount. The age-related rate of mIg-mediated endocytosis by B cells in the MLN, as opposed to a slower rate of endocytosis by B cells in the PP, emphasizes its distinct nature as a mucosal site.(ABSTRACT TRUNCATED AT 250 WORDS)