THE CYTOKINES INTERFERON-γ (IFN-γ) AND INTERLEUKIN 4 (IL-4) PROMOTE TRANSCYTOSIS OF SECRETORY IgA (SIgA) IN HUMAN EPITHELIAL CELLS IN VITRO

Abstract

We have previously demonstrated that the HT-29 human coion carcinoma cell line expresses secretory component (SC), and that culture of these cells with IL-4 and with IFN-γ considerably augments the expression of SC in these cells. Our objective here was to ascertain if this is associated with increased transcytosis of SlgA across the enterocyte. Transparent Biopore membrane inserts were coated with human placental collagen matrix. The coated inserts were placed in 6 well cell cluster culture plates, 36 mm in diameter. On the following day. HT-29 cells maintained in RPMI 1640 were seeded in the inserts in a concentration of 10⁷ cells/ml. RPMI 1640 only was placed in the outer well. Twenty four hours later the cells formed a macroscopic monolayer on the filter. lNF-γ and IL-4 were added in a concentration of 100u/ml each. Forty eight hours later, ¹²⁵I-labelled monomeric IgA (mIgA) (control) and polymeric IgA (pIgA) (test) were added to the inserts. After 24 h, total and SC-associated radioactivity were measured in the fluid of the outer wells. It was found that SC-associatcd radioactivity was 3x higher in the pIg A wells than in the mIgA wells. It was also 3x higher when compared to filters coated with the CaCo 2 human carcinoma cell line, shown by us not to express SC.

CONCLUSION: IFN-γ and IL-4 promote SIgA transcytosis in the HT-29 cell line. Supported by NIH grants 18745, AI-10854. DK-28537 and GIF grant T-79-063.2/88.

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