A study of secretory immunoglobulin A on membranous epithelial cells (M cells) and adjacent absorptive cells of rabbit Peyer's patches.

Secretory immunoglobulin A (SIgA) on the surface of the membranous epithelial cell (M cell) is present in Peyer's patches, an important element of gut-associated lymphoid tissue (GALT). Little information about this immunoglobulin exists except for its scantiness inferred from electron microscopic examination of the relatively thin layer of glycocalyx on the cell surface. This study was undertaken to investigate SIgA on the M cell surface by immunohistochemical observations of specimens from 16-week-old rabbits, using anti-IgA antibody specifically directed to alpha-chain and anti-SIgA antibody specific to both alpha-chain and secretory component (SC). Areas of strongly positive reaction with these antibodies were demonstrable by electron, as well as light microscopy in the glycocalyx layer and on microfolds of M cells, contrasting with the glycocalyx layer and microvilli of the adjacent absorptive cells. The findings were suggestive of an abundant presence of SIgA in the glycocalyx layer and on microfolds of M cells. The results suggested the participation of SIgA on M cell surfaces through a mechanism in which M cells take up intestinal antigens, although the precise role of SIgA on M cells remains unclear.