IgM rheumatoid factor as a source of non-specificity in murine anti-allotype sera

Anti-allotype sera have shown a breakdown of the expected specificity especially when used for the development of haemolysis of fragile target erythrocytes. IgM anti-IgG rheumatoid factor has been shown to be the source of non-specificity. Removal or destruction of IgM in an anti-allotype serum restores the expected specificity.