A method of micro-titration for cytolytic antibodies is described. Standard drops of diluent are placed on a subdivided siliconed slide and dilutions are made by rotating a wire loop holding 1 drop of serum in each drop sequentially. One drop of a mixture of cells and complement is then added. The slide is incubated in a moist chamber for 90 min at 37° C. after which a small cover-slip is placed on each drop and the amount of cell lysis, judged by phase-contrast microscopy, is graded.
An analysis of variance of the method has been performed and the method has been found to be reliable, accurate and unbiased.
It allows accurate estimates of cytolytic activity in sera using cell concentrations of 104 to 105 cells per ml. Eight ten-dilution titrations can be carried out with 1 ml. of such a suspension.