Studies on IgM-κ/IgG mixed cryoglobulin from the standpoint of immuncomplex

Abstract

In this study, a mixed type cryoglobulin (IgM-κ/polyclonal IgG) was analyzed to demonstrate which one of the components had the antibody-like activity to the other, and we tried to analyze the mechanisms of the uniqe thermal characteristics of the cryoglobulin. The following results were obtained.
1) The IgM-protein and the polyclonal IgG obtained from the cryoglobulin did not form cryoprecipitate at 4°C separately.
2) From the recombination experiment of the two cryoglobulin components, it was demonstrated that IgM M-protein and the IgG reacted with each other in nearly 1:1 molar ratio.
3) The cold precipitation reaction was also demonstrated when the IgM-protein from the cryoglobulin was added to the polyclonal IgG and its Fc fragment from normal subject and kept at 4°C.
4) Fabμ, (Fcμ)₅ and IgMs prepared from the IgM M-protein were not able to form cryoprecipitate with polyclonal IgG.
5) All of the reactions of the IgM M-protein with hyarulonidase treated IgG, neuraminidase treated IgG and heated IgG resulted in formation cryoprecipitates which did not redissolve on warming at 37°C.
Based on the above findings, the IgM M-protein was considered to react with polyclonal IgG as a cryoprecipitating factor in this case.
The properties of the antigenic determinant on the IgG molecule may play an immportant role in the occurence of the thermal reaction. The carbohydrate moiety of IgG Fc is one of the very interesting themes for understanding the thermal properties of the cryoglobulin.