The effect of antigen deprivation on thymus-dependent and thymus-independent lymphocytes in the small intestine of the mouse.

Isografts of foetal small intestine, implanted under the kidney capsules of adult mice grow normally and, despite the lack of intraluminal antigenic stimulation, are populated by thymus-dependent and thymus-independent lymphocytes. The Peyer's patches in these grafts are very small, lack germinal centres and can be shown to have small thymus-dependent areas. Quantitative intraepithelial lymphocyte counts were carried out in normally sited small intestine of immunologically intact and thymus-deprived mice, and in grafts implanted in intact and thymus-deprived mice. Counts were also performed in a group of neonatally thymectomized and control mice. The results show a significant depletion of intraepithelial lymphocytes in neonatally thymectomized mice, and a profound reduction in numbers of intraepithelial lymphocytes in grafts, deprived of antigen, when compared with normally sited intestine of the same age.