Delayed-hypersensitivity reactions in the small intestine

Abstract

Lymphoid cells of the small intestine are present both as aggregates, the Peyer’s patches, and as single cells dispersed among the absorptive and stromal tissues of the mucosa. In the lamina propria there are lymphocytes, plasma cells, macrophages, eosinophils and mast cells and many medium-sized lymphocytes are present between the enterocytes — intraepithelial (IE) lymphocytes. The presence of thymus dependent (T) and thymus independent (B) lymphocytes in the intestine, has been demonstrated by morphological examination of the tissues of thymus deprived rodents (Ferguson and Parrott, 1972a), and by studies of cell traffic to the intestine using radioisotope labelling and immunofluor esence (Parrott and Ferguson, 1974; Guy-Grande et al., 1974). the Peyer’s patches are populated by small T and B lymphocytes (as are other peripheral lymphoid tissues such as lymph nodes). However, the lymphocytes and plasma cells of the villi are derived from large lymphocytes — immunoblasts — probably both T and B. The thymus dependence of some intestinal IE lymphocytes has recently been demonstrated by the findings of low IE lymphocyte counts in thymus deprived mice (Ferguson and Parrott, 1972a), and by the homing of radioisotope labelled T immunoblasts to the intraepithelial site (Guy-Grande et al., 1974).