Complement bridges between cells analysis of a possible cell-cell interaction mechanism.

Abstract

Different leukocytes (Raji, Daudi, Rael [human Burkitt''s lymphoma] lymphoid cells; human peripheral blood lymphocytes; and guinea pig granulocytes), which were coated with C3 [3rd component of complement] by incubation at 37.degree. C for 20 min in a C3 solution, formed rosettes with erythrocytes coated with C components (EAC142). The percentage or rosettes was dependent on the amount of C3 present on the cells. Loading of the lymphoid cells with C3 was a time- and temperature-dependent process. C3b was unable to serve the same purpose, although C3 and C3b occupied the C3 receptors on the lymphoid cells to a comparable degree. C5 functions in a similar manner. The .**GRAPHIC**. [activated C4 + C2 complex] enzyme can be replaced by trypsin, so that bridging units may consist of C3 + .**GRAPHIC**. C5 + .**GRAPHIC**. or C3 + trypsin and C5 + trypsin. Bridging units can be constructed also from C4 + C1. Enzymes on 1 cell may liberate labile binding groups of C components on adjacent cells, thus inducing coupling of the 2 cells. This type of cell interlinkage may play a role in vivo, since there is accumulating evidence that C components are expressed in the plasma membrane of different cells.