title: An immunoglobulin light chain dimer with CD4 antigen specificity.
abstract: A subclone that had lost its IgG1 heavy chain was derived from a hybridoma cell line G17-2 that produces an anti-CD4 monoclonal antibody. This subclone was found to secrete a kappa light chain dimer (LCD) that could bind to the CD4 antigen expressed on a subset of human T lymphocytes. The light chain dimer bound to the same or similar epitope as the parental antibody since it blocked the binding of the parenteral anti-CD4 MAb but not the binding of another anti-CD4 MAb G19-2 that recognizes a different epitope. A rabbit anti-idiotype prepared against G17-2 crossreacted with the LCD and could block the antigen binding of both G17-2 and the LCD. Scatchard analysis performed with 35S-methionine or 3H-leucine labelled LCD showed an association constant Ka of 2.2 x 10(7) M-1, whereas the G17-2 parental antibody showed an association constant Ka of 2.5 x 10(9) M-1. These data indicate that the antigen specificity of the G17-2 parental MAb is conferred to a large extent by its light chain. The LCD was expressed on the surface of the LCD-producing hybridoma cells. Southern blot analysis with C kappa and J kappa probes demonstrated a single kappa transcription units which does not have any unusual DNA rearrangements and is distinct from the NS-1 kappa genes. To our knowledge, this LCD is unique in its ability to bind to a large (55,000 mol. wt) glycoprotein antigen.
mesh_terms: D000818:Animals; D000945:Antigens, Differentiation, T-Lymphocyte / Q000276:immunology*; D003429:Cross Reactions; D004591:Electrophoresis, Polyacrylamide Gel; D000939:Epitopes / Q000032:analysis*; D006801:Humans; D007074:Immunoglobulin G / Q000276:immunology; D007145:Immunoglobulin kappa-Chains / Q000276:immunology*; D051379:Mice; D008807:Mice, Inbred BALB C
chemical_list: D000945:Antigens, Differentiation, T-Lymphocyte; D000939:Epitopes; D007074:Immunoglobulin G; D007145:Immunoglobulin kappa-Chains