Properties of IgA-binding receptors on murine T cells: relative importance of Fc alpha R, beta-galactosyltransferase and anti-secretory component reactive proteins (ASCP).
Murine T cells and T-cell lines express receptors for the Fc of IgA (Fc alpha R); however, their molecular properties remain to be elucidated. In the present study, we examined three candidate molecules for IgA-binding receptors including Fc alpha R, beta-galactosyltransferase (beta-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 4-6 and PPT 4-16) and from cloned PP T helper (Th) cell lines (ThHA1 #9 and #10) bound both monomeric and dimeric IgA (mIgA and dIgA), while the fusion partners (BW 5147 and R1.1) did not. In contrast, both Fc alpha R+ and Fc alpha R- cell lines bound to high molecular weight polymeric or aggregated IgA (pIgA). All cell lines reacted with a monoclonal anti-beta-GT (MoAb) and beta-GT enzyme activity was associated with the cell lysates and membrane fractions of all cells tested. The anti-beta-GT MoAb stained a 47-kDa band on immunoblots which was identical to that seen with native enzyme. mRNA analysis with beta-GT cDNA showed that all cell lines constitutively produced enzyme-specific mRNA. Both Fc alpha R+ T cells and Fc alpha R- control cell lines showed cell surface specific beta-GT activity. This is the first study which shows that mouse T cells produce beta-GT. However, Fc alpha R and beta-GT appear to be separate receptors, because Fc alpha R+ T cells bound mIgA and dIgA, and this treatment did not affect staining with biotinylated anti-beta-GT MoAb. Further, preincubation of the Fc alpha R+ cells with anti-beta-GT MoAb did not block mIgA binding. However, the anti-beta-GT MoAb partially blocked binding of pIgA to both Fc alpha R+ and Fc alpha R- T cells, suggesting that beta-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 Fc alpha R+ and Fc alpha R- 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.(ABSTRACT TRUNCATED AT 400 WORDS)
Aicher
W K
WK
Department of Microbiology, University of Alabama, Birmingham 35294.
McGhee
M L
ML
McGhee
J R
JR
Moldoveanu
Z
Z
Kidd
V J
VJ
Tomana
M
M
Mestecky
J
J
Eldridge
J H
JH
Meyer
T F
TF
Kiyono
H
H
D000818:Animals; D005700:Galactosyltransferases / Q000378:metabolism*; D007070:Immunoglobulin A / Q000378:metabolism*; D051379:Mice; D011402:Pronase / Q000494:pharmacology; D011961:Receptors, Fc; D011971:Receptors, Immunologic / Q000737:chemistry / Q000378:metabolism*; D012635:Secretory Component / Q000378:metabolism; D013601:T-Lymphocytes / Q000737:chemistry / Q000201:enzymology / Q000276:immunology*; D014357:Trypsin / Q000494:pharmacology; D010738:Type C Phospholipases / Q000494:pharmacology; D006022:beta-N-Acetylglucosaminylglycopeptide beta-1,4-Galactosyltransferase / Q000737:chemistry / Q000378:metabolism*
C045281:IgA receptor; D007070:Immunoglobulin A; D011961:Receptors, Fc; D011971:Receptors, Immunologic; D012635:Secretory Component; D005700:Galactosyltransferases; D006022:beta-N-Acetylglucosaminylglycopeptide beta-1,4-Galactosyltransferase; D010738:Type C Phospholipases; D014357:Trypsin; D011402:Pronase