Variance of Mouse in the Activity of Complement the Fourth Component

FUKUOKA, Y., OKUDA, T. and TACHIBANA, T. Variance in the Activity o f the Fourth Component of Mouse Complement. Tohoku J. exp. Med., 1983, 141 (2), 225-235 There are two methods for hemolytic titration of 04. One is a method using EACIgP, °XyC2hu and EDTA-CSP (E-C method) and the other using EACIgP, oxyC2hu and C4DSP (C4D mehtod). The 04 titers obtained by these two methods differed depending on whether the 04 exists in plasma or in serum. In the case of Ssh strain, serum 04 activity assayed by the E-C method was higher than that by the C4D method, while plasma 04 activity assayed by the E-C method was lower than that by the C4D method. It was hypothesized that these results would occur from the difference in the state of 04 molecule present in serum or plasma. From chromatographic analysis, it was apparent that the 04 molecule in serum existed in at least four different molecular states; free 04 molecule with low Ss antigenicity, hemolytically inactive Ss protein, active 04 with high molecular weight and low Ss antigenicity, and inactive Ss protein with high molecular weight. Their expression of Ss antigen and the hemolytic 04 activity were different, and each type of 04 molecule behaved differently in the assay of the two methods. Furthermore an important role of mouse 05 in the hemolytic assay of mouse 04 is discussed. 04 activity; Ss antigen; Ss binding protein