Further studies on C9 deficiency.

Further studies were carried out on the C9 deficiency (C9D). Her serum complement activity (CH50) was 15.7 units when assayed in high ionic strength buffer and 8.8 or less than 5.0 units when assayed in low ionic strength buffer containing glucose or sucrose, respectively. It was revealed that this buffer-dependent CH50 variation of C9D serum was due to the effect of the buffer on the spontaneous lysis of EAC1-8. The serum bactericidal activity of C9D was low, but the addition of specific antibody against bacteria increased the activity indicating an important role of antibody in the serum bactericidal activity. Neither C9 inactivator(s) nor antibody against C9 was detected in the serum, indicating that the case had a defect of C9 synthesis. However, the estimation of C9 levels in the sera of her family could not reveal the mode of inheritance of C9D.