Development of the Respiratory Polymeric Immunoglobulin Secretory Immune System (PISIS) in a Porcine Model

The mucosal secretion of polymeric immunoglobulins (Igs) is mediated by the  polymeric immunoglobulin secretory immune system (PISIS), composed by J-chain and antibody producing cells (pAPC), the expression of the polymeric immunoglobulin receptor (pIgR) by epithelial cells and the efficient release of the pIg-pIgR complex to the mucosal lumen. In spite its importance, few detailed studies about their development have been described in humans. Since the porcine model has been reported as an option for translational medicine to humans, we studied the development of the PISIS in trachea and bronchi of healthy, non-vaccinated SPF, miniature Vietnamese pigs, from birth to adulthood using immunohistochemistry and ELISA. Our results showed that colostrum is a source of IgM, SIgA, total IgA and IgG in respiratory secretions (nasal secretion, saliva, trachea and bronchoalveolar lavages) in neonates. Moreover, the pIgR was present at birth, increasing expression with age (Figure). In contrast, pAPCs were low in neonatal pigs, steadily increasing in post-weaned, young and adult pigs. Considerable increases in secretory and total Igs were found in trachea and bronchi with age, correlating with the tissue density of APCs. These data suggest a compensatory role of maternal Igs in the absence of a structured PISIS before weaning. Passive transfer of Igs in elderly people may also compensate PISIS impairment. Besides, it was evident that monomeric Igs may also play an important role in respiratory protection and deserves a more thorough study.

The financial support of CONACyT is acknowledged.