Method for analysis of antigen-antibody precipitins in double immunodiffusion

Ribonucleoprotein (RNP) antigen-antibody precipitin bands obtained by two-dimensional double immunodiffusion were systematically analyzed and compared using a microcomputer and a SPSS-PC statistical analysis package. Precipitins rated in respective agarose concentrations ranging from 0.3% to 1.5% were obtained from twofold dilutions of a calf thymus nuclear extract (CTNE) containing RNP antigen. These dilutions were reacted against the same dilutions of plasma containing anti-RNP antibody. A Mean Quality Index Score was calculated at each agarose concentration from the sum of ratings assigned for the intensity (thickness) of precipitin bands times the sum of ratings assigned for the clarity (clearness and sharpness) of the precipitin bands. This product was divided by the total number of possible precipitin reactions. The Mean Quality Index Score for the 0.4% agarose was significantly higher than the other concentrations (p less than or equal to 0.05). This method or similar approaches may allow a more systematic way of comparing precipitins developed in gel immunodiffusion.