Abstract
Von Krogh's 1 equation, y = x n/(x n + k), has not received the the consideration by immunologists which its very close statement of the facts in several immune mechanisms capable of numerical expression would warrant. It will in general, for instance, closely state the amount of hemolysis in a system where complement is the only independent variable, x, y, is the proportion of hemolysis read colorimetrically, and n and k are constants. It is often more convenient to use it in the form of x n = k[y/(1 − y)]. If this expression is put into logarithmic form,
the expression is linear when expressed graphically, that is, if plotted on logarithmic paper, the data will fall more or less accurately on a straight line whose slope numerically expressed will equal n, and whose intercept on the axis y will be the reciprocal of k. Moreover, if two complements are compared, the intercept of their graphs on the axis of x will be reciprocals of their concentration referred to any unit in which we may choose to express such concentrations.
In theory and this is to a large extent borne out in practice, this intercept on the axis of x is independent of the value of n.
n varies in the case of blood cells with the individual from which the blood is drawn, with the age of the blood cells, and with the treatment which they have experienced. It is low when the cells are suspended in Ringer's solilt ion, high lvhen they are suspended in salt solution, is increased with the age of cells and in general with liarmful conditions, such as the presence of antiseptics in small concentration and the like. It decreases as the concentration of cells is increased, It varies under the conditions and
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