patient's serum other than ABO isoagglutinins (eg, anti-M) may cause a discrepancy in the
reverse grouping. As long as anti-M does not react at 37 C, it is clinically insignificant for
transfusion. However, we found this antibody to be of “immunizing” type which was reactive
at 37 C and AHG phase and showing problems in blood grouping and crossmatch. This
antibody had both IgM and IgG components. When “M” antibodies active at 37 C are …