A laser nephelometric method for measuring alternative pathway complement activity of human and murine serum

A kinetic method for the evaluation of alternative pathway complement activity in man and mice is presented. A laser nephelometer was employed for detection of non-sensitized rabbit erythrocyte lysis based on the observation that the intensity of laser scatter (LS) is proportional to the number of erythrocytes in suspension. During erythrocyte lysis a continuous decline in LS is observed since lytic products do not evoke LS. Utilizing the indirect Coombs test and cross-electrophoresis it was shown that rabbit erythrocyte lysis causes activation of the alternative complement pathway. This method is modified for room temperature, is independent of sample hemoglobin content and, in its micro version, it can be done with 10 microliter of human serum, i.e. 50 microliters of murine serum.