The leukocyte integrin p150,95 (CD11c/CD18) as a receptor for iC3b. Activation by a heterologous beta subunit and localization of a ligand recognition site to the I domain

J Immunol. 1994 May 1;152(9):4582-9.

Abstract

p150,95 is a member of the leukocyte integrin family of adhesion proteins. Compared with LFA-1 and Mac-1, p150,95 is less well functionally characterized. Although p150,95 has complement receptor activity for iC3b and has been designated complement receptor type 4, transfected cells expressing p150,95 do not bind iC3b-sensitized cells. We report that cells cotransfected with a human p150,95 alpha subunit and a chicken, but not human, beta subunit bind IgM-iC3b-coated erythrocytes, suggesting that interactions between the alpha and beta subunits can regulate p150,95 adhesiveness. Furthermore, purified human p150,95 binds to cell-bound iC3b-coated erythrocytes. Because binding to iC3b by cellular and purified p150,95 is specifically abolished by mAbs that localize to the I domain of p150,95, we suggest that the I domain of the p150,95 alpha subunit is an important ligand recognition site for iC3b.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Antibodies, Monoclonal
  • Antigens, CD / genetics
  • Antigens, CD / metabolism*
  • Binding Sites
  • CD11 Antigens
  • CD18 Antigens
  • Cell Line
  • Chickens
  • Chlorocebus aethiops
  • Complement C3b / metabolism*
  • Epitopes
  • Erythrocytes / immunology
  • Humans
  • Leukocytes / immunology
  • Leukocytes / metabolism
  • Ligands
  • Receptors, Complement 3b / genetics
  • Receptors, Complement 3b / metabolism*
  • Recombinant Proteins / genetics
  • Recombinant Proteins / immunology
  • Recombinant Proteins / metabolism
  • Rosette Formation
  • Transfection

Substances

  • Antibodies, Monoclonal
  • Antigens, CD
  • CD11 Antigens
  • CD18 Antigens
  • Epitopes
  • Ligands
  • Receptors, Complement 3b
  • Recombinant Proteins
  • Complement C3b