CD4/immunoglobulin interaction: implications for immune physiology and autoimmunity.
CD4 has an important role in T cell activation events that depend on its binding to non-polymorphic MHC class II determinants on antigen-presenting cells. Here, we provide evidence that CD4 also interacts with immunoglobulins (Ig). The Ig-binding region lies within residues 21-49 of V1 domain of CD4. Immunochemical studies suggest that this property of CD4 does not depend on the three-dimensional folding of the CD4 molecule. Synthetic peptides (p) encompassing amino acid residues 16-49 and 21-49 of CD4 bind immunoglobulins in comparable way to the intact molecule. In vitro p 16-49 enhances significantly idiotype/anti-idiotype and some weak antigen-antibody interactions. Antigen antibody complexes formed in antigen excess bind CD4 peptides with much higher avidity then non-complexed antibodies. The possible role of the CD4/Ig interaction in T-B cell cooperation is discussed.
Lenert
P
P
Department of Medicine, University of California, San Diego 92103.
Zanetti
M
M
D000818:Animals; D000936:Antigen-Antibody Complex / Q000276:immunology; D015551:Autoimmunity / Q000276:immunology*; D015704:CD4 Antigens / Q000276:immunology*; D006801:Humans; D007107:Immune System / Q000502:physiology*; D007074:Immunoglobulin G / Q000276:immunology*
D000936:Antigen-Antibody Complex; D015704:CD4 Antigens; D007074:Immunoglobulin G