Presence of IgA-producing cells in rats and mice in relation to microbial status

Summary The numbers of IgA-producing cells in intestinal mucosa, mesenteric lymph nodes, lungs and bronchial lymph nodes were scored in rats and mice. A statistically significant difference in the scores existed between germ-free and SPF mice and between gnotobiotic and SPF rats. In a group of SPF rats a statistically significant difference in the scores was demonstrated in relation to several bacterial and viral agents. The normal intestinal mucosa is densely infiltrated by large numbers of plasma cells. Crabbe, Barin, Eyssen & Heremans (1968) demonstrated the abundance of IgA-producing cells among the mucosal plasma cells in the gut of conventional mice as compared with the scarcity of these cells in germ-free (GF) mice. The normal microbial flora was regarded as the major stimulus for proliferation of these cells. After histological comparison of the intestinal walls of SPF mice, GF mice and mice associated with different non-pathogenic anaerobic microfloras (Koopman, Mullink, Prins, Welling & Hectors, 1982), the number of IgA-producing cells and the villus-crypt ratio appeared suitable tools to distinguish between these groups. Usually, monitoring of laboratory animal colonies is confined to the direct demonstration of presence or absence of bacteria and parasites and to indirect demonstration of viruses by serological methods. Consideration of the significance of the findings is based on the type of micro-organisms found. Production of IgA is considered to be the first reaction after invasion of pathogens (Sell, 1972). This idea, together with an observed difference in IgA-producing cells among SPF rats and mice, led to a study of the relationship between the microbial burden of rats and mice and the number of IgA-producing cells. The results of this study are reported in the present paper.