Variant expression of lactate dehydrogenase complexes, interfering with isoenzyme analysis.

Three patients with an elevated serum LD activity and unusual, but quite different LD isoenzyme patterns, were studied. It was shown by immunofixation procedures, that complexes between LD isoenzymes and immunoglobulins of the IgG-kappa, IgA-kappa and IgG-lambda class, respectively, caused the observed isoenzyme patterns. From mixing experiments it appeared that the immunoglobulins were specific for either the H-subunit only or an antigenic determinant expressed by a combination of H- and M-subunits in the LD isoenzymes. The observed complexes could be dissociated, in vitro, with NAD+ in two patients, while in the third patient the complex was resistant to NAD+ addition. No common denominator was found with respect to clinical diagnosis. Auto-immune disorders or infection with hepatitis B virus were not involved.