Studies on the mechanism of LDH-IgG complex formation using 5'-AMP and Cibacron Blue F3G-A affinity chromatography

Abstract

In this report, we described the differences between the LDH-IgG complexes in patient's sera (ten cases) and anti-LDH5 antibody in affinity to 5'-AMP and Cibacron Blue F3G-A. LDH-IgG complexes in all cases were dissociated either by passing the patient's serum through a column containing 5'-AMP-Sepharose 4B or Blue Sepharose CL-6B-e.g., the electrophoretic LDH isoenzyme pattern for concentrated bound fraction was normal. Although the unbound fraction was devoid of LDH activity, a mixture of this fraction and normal serum had the same abnormal pattern as the patient's serum alone. However, this was not true for a mixture of anti-LDH5 antiserum and normal serum.We propose the following hypothesis for the LDH-IgG complex formation: LDH can recognize the abnormal γ-Fab region of IgG which show similarities with the conformation of NAD+ at the NAD+ binding site of the molecule, but the affinity of the LDH molecule for immunoglobulin is much weaker than that for NADH or 5'-AMP.