|
||
Original Article |
anichols{at}caregroup.harvard.edu
Mannan-binding lectin (MBL), a member of the collectin family, is known to have opsonic function, although identification of its cellular receptor has been elusive. Complement C1q, which is homologous to MBL, binds to complement receptor 1 (CR1/CD35), and thus we investigated whether CR1 also functions as the MBL receptor. Radioiodinated MBL bound to recombinant soluble CR1 (sCR1) that had been immobilized on plastic with an apparent equilibrium dissociation constant of 5 nM. N-acetyl-D-glucosamine did not inhibit sCR1–MBL binding, indicating that the carbohydrate binding site of MBL is not involved in binding CR1. C1q inhibited MBL binding to immobilized sCR1, suggesting that MBL and C1q might bind to the same or adjacent sites on CR1. MBL binding to polymorphonuclear leukocytes (PMNs) was associated positively with changes in CR1 expression induced by phorbol myristate acetate. Finally, CR1 mediated the adhesion of human erythrocytes to immobilized MBL and functioned as a phagocytic receptor on PMNs for MBL–immunoglobulin G opsonized bacteria. Thus, MBL binds to both recombinant sCR1 and cellular CR1, which supports the role of CR1 as a cellular receptor for the collectin MBL.
Key Words: C1q opsonins neutrophil erythrocyte innate immunity
I. Ghiran and S.F. Barbashov contributed equally to this work.
S.F. Barbashov's present address is Protein Division, Ilex Oncology Corporation, Boston, MA 02215.
Abbreviations used in this paper: CR1, complement receptor 1; CRD, carbohydrate recognition domain; C1qRp, C1q receptor of phagocytosis; LHR, long homologous repeat; MASP, MBL-associated serine protease; MBL, mannan-binding lectin; MFC, mean fluorescent channel; sCR1, soluble CR1; TBS, Tris-buffered saline.
© 2000 The Rockefeller University Press
![]()
CiteULike
Complore
Connotea
Del.icio.us
Digg
Facebook
Reddit
Technorati
Twitter What's this?
| TABLE OF CONTENTS |
|