In Vitro Kinetics of Intestinal Secretory IgA Secretion

Locally synthesized secretory IgA (sIgA)3 is the predominant immunoglobulin in most mammalian external secretions (1). In the intestinal tract, the sIgA molecule is thought to be a synthetic product of lamina propria plasma cells (i.e., heavy (H) and light (L) chains, and J chain) and mucosal epithelial cells (i.e., secretory component) (1–3). Because appropriate models have not been available, it has not been possible to examine directly the kinetics of sIgA secretion. We have recently shown (4) that biopsies of rabbit small intestine maintained in organ culture synthesized and secreted protein in vitro under steady-state conditions for at least 24 hr. Furthermore, these biopsies synthesized sIgA de novo and secreted intact sIgA into the organ culture medium. The present paper describes the kinetics of sIgA secretion by rabbit intestinal mucosa in vitro. Rabbit small intestinal biopsies consisting largely of mucosa and submucosa were placed in organ culture as described in detail previously (4, 5).