Properties of IgA‐Binding Receptors on Murine T Cells: Relative Importance of FcαR, β‐Galactosyltransferase and Anti‐Secretory Component Reactive Proteins (ASCP)

Academic Article

Abstract

  • Murine T cells and T‐cell lines express receptors for the Fc of IgA (FcαR); however, their molecular properties remain to be elucidated. In the present study, we examined three candidate molecules for IgA‐binding receptors including FcαR, β‐galactosyltransferase (β‐GT) and anti‐secretory component (SC) reactive proteins (ASCP) expressed on T cells which might participate in the binding of different molecular forms of IgA. T‐cell lines derived from CD4+ T cells of mouse Peyer's patches (PP) (designated PPT 4–6and PPT 4–16) and from cloned PP T helper (Th) cell lines (ThHA1#9and #10) bound both monomeric and dimeric IgA (mIgA and dIgA), while the fusion partners (BW 5147 and R 1.1) did not. In contrast, both FcαR+ and FcαR‐ cell lines bound to high molecular weight polymeric or aggregated IgA (pIgA). All cell lines reacted with a monoclonal anti‐β‐GT(MoAb) and β‐GT enzyme activity was associated with the cell lysates and membrane fractions of all cells tested. The anti‐β‐GT MoAb stained a 47‐kDa band on immunoblots which was identical to that seen with native enzyme. mRNA analysis with β‐GT cDNA showed that all cell lines constitutively produced enzyme‐specific mRNA. Both FcαR+ T cells and FcαR‐ control cell lines showed cell surface specific β‐GT activity. This is the first study which shows that mouse T cells produce β‐GT. However, FcαR and β‐GT appear to be separate receptors, because FcαR+ T cells bound mIgA and dIgA, and this treatment did not affect staining with biotinylated anti‐β‐GT MoAb. Further, preincubation of the FcαR+ cells with anti‐β‐GT MoAb did not block mIgA binding. However, the anti‐β‐GT MoAb partially blocked binding of pIgA to both FcαR+ and FcαR‐ T cells, suggesting that β‐GT may be a receptor for pIgA. Others have shown that T cells may bind IgA through a receptor serologically related to SC. We found that antibodies both to human SC and to rat SC specifically bound to both FcαR+ and FcαR‐ T cells. Further, a 72‐kDa band was detected when cell membrane fractions were analysed with these antisera (ASCP) by solid phase immunoisolation technique and immunoblot analysis. The ASCP is not an IgA‐binding receptor, since anti‐SC did not block either mIgA or pIgA binding. Further, the effects of proteolytic enzymes were different on these three IgA‐binding molecule candidates. FcαR and ASCP were shown to be sensitive to pronase proteolytic degradation, but were resistant to trypsin and trypsin/EDTA treatments. In contrast, β‐GT was sensitive to both pronase and trypsin treatments. We conclude that multiple IgA receptors are present on mouse T cells, and include those which bind to mIgA or dIgA (FcαR) as well as those which bind to pIgA (β‐GT). Further, ASCP is also present on mouse T‐cell lines, but its role in IgA binding to T cells remains to be further determined. Copyright © 1992, Wiley Blackwell. All rights reserved
  • Published In

    Digital Object Identifier (doi)

    Author List

  • AICHER WK; McGHEE ML; McGHEE JR; MOLDOVEANU Z; KIDD VJ; TOMANA M; MESTECKY J; ELDRIDGE JH; MEYER TF; KIYONO H
  • Start Page

  • 469
  • End Page

  • 486
  • Volume

  • 35
  • Issue

  • 4