Structural differences between the two human complement C4 isotypes affect the humoral immune response

J Exp Med. 1992 Feb 1;175(2):537-43. doi: 10.1084/jem.175.2.537.


An animal model has been used to address the question of the biological importance of the known structural difference between the two isotypes of human C4, i.e., C4A and C4B. Guinea pigs deficient in C4 were reconstituted transiently with either human C4A or C4B protein and immunized with the bacteriophage phi X174. Results from this study showed that C4A-reconstituted animals made a secondary response, i.e., switch from IgM to IgG; whereas the C4B-reconstituted animals did not.

Publication types

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

MeSH terms

  • Animals
  • Antibody Formation*
  • Bacteriophages / immunology
  • Complement C4a / deficiency
  • Complement C4a / immunology*
  • Complement C4a / isolation & purification
  • Complement C4b / deficiency
  • Complement C4b / immunology*
  • Complement C4b / isolation & purification
  • Disease Models, Animal
  • Escherichia coli / immunology
  • Guinea Pigs
  • Humans
  • Immunoglobulin G / genetics
  • Immunoglobulin Isotypes / immunology*
  • Immunoglobulin M / genetics
  • Immunoglobulin Switch Region / immunology
  • Male
  • Structure-Activity Relationship


  • Immunoglobulin G
  • Immunoglobulin Isotypes
  • Immunoglobulin M
  • Complement C4a
  • Complement C4b