Cell cycle control of activated, synchronized murine B lymphocytes--roles of macrophages and complement C3.
Three restriction points control the cell cycle of activated murine B lymphocytes in a synergistic way. The first is controlled by the occupancy of surface immunoglobulin either by antigen- or by immunoglobulin-specific antibodies. The second is controlled by the complement C3d receptor CR2 which can be occupied by cross-linked C3b or C3d to stimulate the entry into S phase, or by soluble C3d or a C3 alpha-chain peptide, binding to the CR2 receptor, which inhibit the entry into S phase. Macrophages produce so-called alpha factors which also control the B-cell cycle at the same point. Thus, it is suspected that macrophages produce components of the early pathway of complement activation which finally lead to cross-linking of CR2 receptors on B cells. The third restriction point is controlled by unknown receptors that recognize so-called beta factors produced by helper T lymphocytes.
D000818:Animals; D001402:B-Lymphocytes / Q000166:cytology / Q000276:immunology*; D002453:Cell Cycle; D003176:Complement C3 / Q000276:immunology*; D003179:Complement C3b / Q000276:immunology; D015933:Complement C3d; D008213:Lymphocyte Activation; D008222:Lymphokines / Q000276:immunology; D008264:Macrophages / Q000276:immunology*; D051379:Mice; D011951:Receptors, Complement / Q000276:immunology; D017464:Receptors, Complement 3d
D003176:Complement C3; D008222:Lymphokines; D011951:Receptors, Complement; D017464:Receptors, Complement 3d; D003179:Complement C3b; D015933:Complement C3d