A Simplified Photronreflectometric Technic for the Titration of the Antibody-Potency of Antipneumococcal Horse and Rabbit Serum

[摘要] A previous report (1) described a quantitative photronreflectometric technic for the determination of the antibody-potency of type I and II antipneumococcal horse-serum. The present paper outlines a simplified technic for determining the potency of all types of antipneumococcal horse- and rabbit-serum. The titrations are carried out at a definite reference-point on the antigen-antibody curve, that is, at the point of optimal precipitation in the zone of a slight excess of antigen. For the determination of this point, a rapid method is given which consists in mixing equal parts of varying dilutions of a serum of known potency and a constant concentration of the type-specific capsular polysaccharide and reading the resulting turbidities by means of the photronreflectometer. The maximal ratio of photronreflectometric reading to percentile serum-dilution indicates the point of optimal precipitation. The antibody-potency of samples of unknown serum may be determined by titrating varying dilutions of the unknown serum with the concentration of SSS used in determining the point of optimal precipitation. The end-point of the titration is the photronreflectometric reading originally obtained at this point with a serum of known potency. The unit-content of the unknown sample can be calculated by multiplying the turbidity reading of the unknown by the units per galvanometric scale-interval (obtained from the original titration with a serum of known potency) and dividing by the percentile serum-dilution.The simplified photronreflectometric technic has several distinct advantages over the technic outlined in a previous report (1); in that the number of standardized SSS dilutions have been reduced from approximately 20 to a single dilution for each type, thus saving considerable time in preparing and standardizing solutions; a more definite and easily determined reference-point (point of optimal precipitation) is utilized as the end-point and finally, it is possible to titrate both antipneumococcal horse- and rabbit-serum at the point of optimal precipitation. Data are given to show that rabbit-serum cannot be titrated in the zone of a slight excess of antibody as proposed for types I and II horse-serum in a previous paper.The data show that repeated photronreflectometric readings of the same concentrations of serum and SSS have a high degree of constancy. It is also shown that a reasonably good correlation exists between the unit-content of a serum determined by photronreflectometric titrations and that determined by the mouse-protective test.

[学科分类] 生物科学（综合）