Affinity chromatography of pIgGs (mixture of 10 preparations) on anti-IgG1 (A), anti-IgG2 (B), anti-IgG3 (C) and anti-IgG4 (D) Sepharose: (—), absorbance at 280 nm, (□) and (▪), relative catalytic activities (RA) in the hydrolysis of hMBP and OP-19, respectively. Depending on the RA, the reaction mixtures were incubated for 0.3–16 hrs in the presence of 10–100 mg/ml IgGs and then the RAs were normalized to the standard conditions: the complete transition of 0.19 mg/ml hMBP 0.33 mM OP-19 to their hydrolyzed forms in the presence of 0.1 mg/ml pIgGs after 1 hr of incubation was taken for 100%. The average error in the initial rate determination from two experiments in each case did not exceed 7–10%.