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C8 binding protein bears I antigenic determinants

P Blaas-Mautner1, S Filsinger, B Berger

  • 1Institut für Immunologie der Universität Heidelberg, Federal Republic of Germany.

Annals of Hematology
|February 1, 1991
PubMed

Insights

The I antigen, a sugar sequence on red blood cells, is linked to C8 binding protein (C8bp). Removing the I antigen does not affect C8bp

Area of Science:

  • Immunology
  • Glycobiology
  • Complement System

Background:

  • C8 binding protein (C8bp) is a membrane glycoprotein on blood cells.
  • C8bp inhibits C5b-9-mediated lysis in homologous systems.
  • The I antigenic determinant is a sugar sequence found on adult human erythrocytes.

Purpose of the Study:

  • To analyze the carbohydrate portion of C8bp.
  • To determine if the I antigenic determinant is essential for C8bp function.
  • To investigate the role of I antigen in homologous species restriction.

Main Methods:

  • Analysis of the carbohydrate structure of C8bp.
  • Enzymatic cleavage of the I antigenic determinant from C8bp using endo-beta-galactosidase (E.C. 3.2.2.103).
  • Treatment of intact erythrocytes with endo-beta-galactosidase.

Main Results:

  • C8bp was found to be associated with the I antigenic determinant.
  • Enzyme treatment removed the I antigen from C8bp without affecting its inhibitory function.
  • Treatment of erythrocytes removed I antigen but did not abolish resistance to homologous C5b-9 lysis.

Conclusions:

  • The I antigen is associated with C8bp.
  • The presence of the I antigen is not required for the homologous species restriction mediated by C8bp.

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