A new immuno quantitative method by latex agglutination--application for the determination of serum C-reactive protein (CRP) and its clinical significance.

We developed a new method for the determination of CRP by latex immunoassay which measures the increase in optical density as a result of latex agglutination due to antigen-antibody reaction. This latex agglutination photometric immunoassay can be used for quantitative analysis of various biological substances. We have established the best conditions for CRP determination for the instrument employed here (LA system) which allows rapid and accurate to low concentration measurement. The measurement range of the system is from 0.01-3 mg/l (non-diluted method), which when compared to the lower detection limit of RIA, 3 micrograms/l, it has the same order of magnitude. It is more sensitive than radial immunodiffusion which has the lower detection limit of 2 mg/l and has the similar value to that of radio-electroimmunodiffusion, 10 micrograms/l. Furthermore, the usual method used in the clinical laboratories, the capillary microprecipitation method, has the lower detection limit of approximately 10 mg/l. The method presented here is adequately sensitive to measure the low concentration of CRP among healthy individuals which has not been possible except by using RIA. The normal value derived from 106 healthy individuals by this method is found to be 0.2 +/- 0.2 mg/l (mean +/- 2SD).

Macro creatine kinase: a study on CK-linked immunoglobulin.

We describe three cases in which creatine kinase (CK, EC 2.7.3.2) was linked to immunoglobulin in serum. In this study, its prevalence was 0.8%. Enzyme-immunofixation electrophoresis revealed that the heavy chain of CK-linked immunoglobulins was of class alpha in all cases. The light-chain type was identified as lambda in two cases and as both lambda and kappa in one case. The complexes were dissociated at pH 3.4 and re-formed with CK isoenzymes MM and MB at pH 7.4. The complex fraction obtained by gel filtration was not inhibited by anti-CK-M antibodies. Treatment of the serum with urea after heating shows residual CK-MM activity; in contrast, normal CK activity disappeared entirely after this treatment. The present study suggests that CK-linked immunoglobulins may be one of the circulating immune complexes and must be distinguished from other macro-CK in the strict sense. The results obtained show that the presence of the complexes results in false-positive CK-B activity in the immuno-inhibition test, and they may provide interesting insights into the mode of binding of the CK-linked immunoglobulins.

Creatine kinase isoenzyme of high relative molecular mass in serum of a cancer patient.

We describe an atypical serum creatine kinase isoenzyme in the serum of a woman with cancer of the left breast. This isoenzyme migrated toward the cathode, closely following the MM isoenzyme on agarose gel electrophoresis. Its relative molecular mass was estimated to be about 325,000, fourfold that of normal creatine kinase. It is more heat-stable and is inhibited more by urea than the normal MM isoenzyme. Isoenzyme monomer B activity was observed to be 20 U/liter in the serum, as measured with use of an antibody against the M monomer. On anion-exchange column analysis, creatine kinase activity was observed only in the MM fraction, in spite of the fact that B activity was observed in the patient's serum. Results of the immunological investigation make it unlikely that the atypical isoenzyme is linked to immunoglobulin or beta-lipoprotein. It may have been present as the result of modification of normal creatine kinase by the therapeutic radiation the patient was receiving.