1990 年 19 巻 4 号 p. 346-349
The relationship between P-endorphin and immunoglobulins was studied by examining the reaction of human and various animal IgGs to human β-endorphin radioimmunoassay (RIA).
The dilution curves of the highly purified IgGs of the human, rabbit, rat, guinea pig and goat samples, demonstrated 0.18%, 0.052%, 0.038%, 0.008%, 0.008%, and 0.007% displacement reactivity respectively, to the human P-endorphin standard curve, with good parallelism. These immunological parallels to human β-endorphin suggest that a part of the amino acid sequence of human and mammalian IgG is similar to that of human P-endorphin. Therefore, it can be speculated that this relationship between IgG and β-endorphin arises from the same origin in evolutionary terms, a possibility that needs further clarification.
Consequently, certain caution is warranted while interpreting the β-endorphin values obtained by the RIA using polyclonal antibody, particularly in a patient with high IgG levels, the cross-reaction makes the β-endorphin level spuriously high and to avoid IgG interference using a specific monoclonal antibody to synthetic β-endorphin is preferable to using polyclonal antibodies raised in animals.