cytochalasin-b and Agammaglobulinemia

The immunoglobulins produced by the earliest recognizable B cell precursors (pre-B cells) were characterized in the mouse and human. Immunofluorescent analysis revealed no evidence of surface IgM components, and only mu heavy chains could be detected intracytoplasmically in pre-B cells. Surface IgM components could not be isolated from intact fetal liver cells that lacked sIgM+ B lymphocytes but possessed pre-B cells. Pre-B cells were shown to synthesize and secrete mu heavy chains but not light chains by immunochemical analysis. These mu chains constituted less than 0.01% of TCA precipitable protein synthesized and secreted by fetal liver cells during an 8 hr labelling period. Migration of both intracellular and secreted mu chains on SDS-PAGE suggested that they were smaller than mu chains secreted by mouse and human plasmacytomas. These data indicate that mu chain synthesis precedes light chain expression during B cell ontogeny and suggest a new role for pre-B cells in the generation and expression of a diverse immunoglobulin repertoire.

Topics: Agammaglobulinemia; Animals; B-Lymphocytes; Cytochalasin B; Humans; Immunoglobulin Heavy Chains; Immunoglobulin Light Chains; Immunoglobulin M; Immunoglobulin mu-Chains; Liver; Male; Mice; Mice, Inbred CBA; Receptors, Antigen, B-Cell

Topics: Agammaglobulinemia; Antibodies, Anti-Idiotypic; Antigen-Antibody Complex; Azides; Binding Sites, Antibody; Cell Membrane; Cytochalasin B; Epitopes; Fluorescent Antibody Technique; Humans; Immunoglobulin G; Immunoglobulins; Leukemia, Lymphoid; Lymphocyte Activation; Lymphocytes; Pinocytosis; Pronase; Sarcoidosis; Sodium; Trypsin