Functional and biochemical properties of the early classical complement system of mice

Mouse serum and EDTA plasma were subjected to low ionicity precipitation, gel filtration, and ion exchange chromatography in an attempt to purify C1, C4, and C2 to functional and chemical homogeneity. In marked contrast to human and guinea pig components, those of the mouse could not be separated by these techniques. Except for partial separation of C1 from C4 and C2 on DE-52 cellulose columuns with EDTA in the eluting buffers, there was no separation of those three components on ion exchange chromatographic columns. Sephadex G-200 gel filtration columns, or with precipitation of euglobulins from serum or plasma. Generation of EAC142 by incubation of EA in whole serum followed first order kinetics when mouse serum was used and second (or greater) order kinetics when human or guinea pig sera were used. Generation of EAC142 by incubation of EA in whole mouse serum followed by incubation in EDTA containing buffers resulted in rapid loss of all three activities from the cell. These experiments indicated that there were significant differences between the early classical C system of mice and those of human and guinea pig. In addition, they indicated that under a variety of in vitro conditions, murine C1, C4, and C2 behaved biochemically and functionally as a unit. The reasons for the major differences in behavior of the murine C components with not become clear until methods to stabilize their function are found so that they can survive multiple purification steps.