Light microscopic morphometric analysis of rat ileal mucosa. I. Component quantitation of IgA-containing immunocytes.

A light microscopic morphometric analysis of IgA-containing immunocytes within samples of ileal mucosa was performed. The following groups of rats were studied: (1) animals raised in a gnotobiotic environment (microbial reduction); (2) animals with iatrogenic self-filling intestinal blind loops (microbial proliferation); and (3) control animals (sham operation). The unlabeled antibody enzyme immunohistochemical localization technique was employed for the identification of intracellular IgA. Component quantitation involved use of a micrometer component quantitator. Numerical density of the immunocyte population was determined by component quantitation of individual and total immunocyte volumes and by application of the Floderus equation. The methodology employed provided a precise quantitative analysis of all mucosal components of normal and manipulated rat ileum. A statistically significant reduction in the volume percentage of IgA-containing immunocytes in association with both microbial reduction and microbial proliferation was observed. The volume percentage reduction of the IgA-containing immunocyte population associated with gnotobiosis may reflect decreased microbial antigenic stimulation, whereas that associated with microbial proliferation may reflect the presence of an increased population of immunocytes producing non-IgA immunoglobulins.