The Relationship of the Haemolytic Activity of Complement to the Concentration of Sensitized Erythrocytes.

The relationship of the haemolytic activity of complement (C′) to the concentration of sensitized erythrocytes (EA) has been found subject to precise mathematical definition, on the basis of data obtained from simultaneous C′ titrations carried out with twelve different EA concentrations ranging from10₇ EA/ml. to 2 × 10⁹ EA/ml. Increase in EA concentration is accompanied by increase both in the amount of C′ required for 50 per cent haemolysis (RD₅₀ C′), and in the value of σ (reciprocal of the slope of the curve relating probit percentage haemolysis to log C′). The relationship of RD₅₀ C′ to EA concentration is an exponential one; the equation expressing this relationship contains a parameter which is interpreted as consistent with the existence of a threshold value of C′ which should be taken into account in assessing RD₅₀ C′. An explanation of the increase in RD₅₀ C′ and σ with increase in EA concentration is offered. [ABSTRACT FROM AUTHOR]