A study of the character and function of the lymphoid cell population in the epithelium of the small intestinal villi of the mouse

The lymphoid cell population in the small intestinal epithelium of the mouse was studied by light, fluorescence and electron microscopy. The origin and kinetics of this population was examined by autoradiography. The population was found to have the following characteristics. It is composed of morphologically different cell types. The majority of the cells are small or medium lymphocytes, but occasionally, large pyroninophilic cells are observed, and even less frequently plasma cells are found. The cells are situated between the absorptive epithelial cells, and the majority lie close to the basement membrane. In keeping with the low incidence of pyroninophilic cells, fluorescence studies indicated that the majority of cells do not contain large amounts of antibody.

The population is composed of at least two subpopulations with different lifespans, one of which is short-lived and the other long-lived. The origin of these cells is not clear, but the presence of mitotic figures in the epithelium indicates that the population is in part self-replicating. Cell transfer studies suggest that several cell sources can contribute a few cells to the epithelium, and therefore this population is probably complex in its origin. The fate of these cells is equally complex, a few degenerate, some migrate into the lamina propria and the others are presumably lost into the lumen of the intestine.

The function of this population is unknown, but a role in digestion, antibody production or as a bursal equivalent would tend to be excluded by the results. The hypothesis is presented that these cells are involved in cell-mediated immune responses either as a cellular equivalent of the local IgA antibody system, or alternatively, as cell mediators involved in the regulation of tissue growth.

The lymphoid cell population in the small intestinal epithelium of the mouse was studied by light, fluorescence and electron microscopy. The origin and kinetics of this population was examined by autoradiography. The population was found to have the following characteristics. It is composed of morphologically different cell types. The majority of the cells are small or medium lymphocytes, but occasionally, large pyroninophilic cells are observed, and even less frequently plasma cells are found. The cells are situated between the absorptive epithelial cells, and the majority lie close to the basement membrane. In keeping with the low incidence of pyroninophilic cells, fluorescence studies indicated that the majority of cells do not contain large amounts of antibody.

The population is composed of at least two subpopulations with different lifespans, one of which is short-lived and the other long-lived. The origin of these cells is not clear, but the presence of mitotic figures in the epithelium indicates that the population is in part selfreplicating. Cell transfer studies suggest that several cell sources can contribute a few cells to the epithelium, and therefore this population is probably complex in its origin. The fate of these cells is equally complex, a few degenerate, some migrate into the lamina propria and the others are presumably lost into the lumen of the intestine.

The function of this population is unknown, but a role in digestion, antibody production or as a bursal equivalent would tend to be excluded by the results. The hypothesis is presented that these cells are involved in cell-mediated immune responses either as a cellular equivalent of the local IgA antibody system, or alternatively, as cell mediators involved in the regulation of tissue growth.