The relative distribution of IgM and IgA cells in intestinal mucosa and lymphoid tissues of the young unweaned pig and their significance in ontogenesis of secretory immunity.

A comparative study of cells synthesizing immunoglobulins IgA and IgM in intestinal mucosa and various lymphoid tissues of unweaned piglets has been made by immunofluorescence. The lamina propria of the small intestine contained as many cells synthesizing IgM as those producing IgA. In all other lymphoid organs examined, including Peyer's patches, the number of IgM cells was significantly higher. The largest population of intestinal immunocytes occurred in the lamina propria of the duodenum where the counts were ten times greater than in the jejunum or ileum. The relevance of these findings to the earliest stages of development of secretory immunity in the young pig are considered.