Polymeric Immunoglobin (Ig) Receptor Production and IgA Transcytosis in Polarized Primary Cultures of Mature Rat Uterine Epithelial Cells1
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These studies were conducted to more fully understand the role of uterine epithelial cells (UEC) in immunoglobin (Ig)A movement from tissue into secretions in the female reproductive tract. Indirect immunofluorescence and image analysis showed that the polymeric Ig receptor (pIgR), which is responsible for transporting polymeric IgA (pIgA) across epithelial cells, was expressed in uterine tissues from rats throughout the estrous cycle. UEC pIgR levels were higher at estrus than at either proestrus or diestrus. When UEC were isolated from the uteri of adult rats and grown on cell culture inserts, cells grew to confluence, formed tight junctions, and released secretory component (SC), the external domain of the pIgR, into the apical medium. Irrespective of whether UEC were isolated from the uteri of rats at the diestrous, proestrous, or estrous stages of the reproductive cycle, cells produced SC, indicating that they are capable of IgA transport. 125I-IgA was preferentially transcytosed from the basolateral to the apical surface, demonstrating that dimeric IgA (dIgA) could be transported by UEC in culture. In contrast, the fluid phase marker [3H]inulin moved at a comparable rate in both directions across the cell monolayer. 125I-IgA transport through UEC was saturable and specific for pIgA in that unlabeled pIgA, but not IgG, inhibited 125I-dIgA transcytosis from the basolateral to the apical surface. Immunoprecipitation of 125I-IgA in the apical chamber with rabbit anti-SC antibody indicated that after transepithelial movement, IgA was bound to SC. Northern blot analysis of RNA extracted from UEC demonstrated that cells continued to synthesize pIgR mRNA in culture. Our results suggest that in the uterus, epithelial cells play a key regulatory role in the control of IgA transcytosis from tissue into secretions.