POLYMERIC IMMUNOGLOBIN (IG) RECEPTOR PRODUCTION AND IGA TRANSCYTOSIS IN POLARIZED PRIMARY CULTURES OF MATURE RAT UTERINE EPITHELIAL-CELLS

These studies were conducted to more fully understand the role of uter ine epithelial cells (UEC) in immunoglobin (Ig)A movement from tissue into secretions in the female reproductive tract, Indirect immunofluor escence and image analysis showed that the polymeric Ig receptor (pIgR ), which is responsible for transporting polymeric IgA (pIgA) across e pithelial cells, was expressed in uterine tissues from rats throughout the estrous cycle. UEC pIgR levels were higher at estrus than at eith er proestrus or diestrus. When UEC were isolated from the uteri of adu lt rats and grown on cell culture inserts, cells grew to confluence, f ormed tight junctions, and released secretory component (SC), the exte rnal domain of the pIgR, into the apical medium. Irrespective of wheth er UEC were isolated from the uteri of rats at the diestrous, proestro us, or estrous stages of the reproductive cycle, cells produced SC, in dicating that they are capable of IgA transport. (125)HgA was preferen tially transcytosed from the basolateral to the apical surface, demons trating that dimeric IgA (dIgA) could be transported by UEC in culture . In contrast, the fluid phase marker [H-3]inulin moved at a comparabl e rate in both directions across the cell monolayer. (125)-HgA transpo rt through UEC was saturable and specific for pIgA in that unlabeled p IgA, but not IgG, inhibited I-125-dIgA transcytosis from the basolater al to the apical surface. Immunoprecipitation of 125-HgA in the apical chamber with rabbit anti-SC antibody indicated that after transepithe lial movement, IgA was bound to SC. Northern blot analysis of RNA extr acted from UEC demonstrated that cells continued to synthesize pIgR mR NA in culture. Our results suggest that in the uterus, epithelial cell s play a key regulatory role in the control of IgA transcytosis from t issue into secretions.