Importance of Clinically Significant Anti-M Antibody in Hematopoietic Stem Cell Transplantation.

Naturally occurring anti-M antibodies are mostly of the IgM class, however, an IgG component can also be present along with IgM. The IgM anti-M antibodies can be ignored if they are not reactive at 37 °C, but the patient should receive M antigen-negative red blood cells if the antibody is reactive at 37 °C or if it is of IgG class. Here we discuss a case of clinically significant naturally occurring anti-M antibody had both IgM and IgG components in a 3 years old child who was a hematopoietic stem cell donor for her 6 years old sister suffering from beta-thalassemia major. The specificity and immunoglobulin class of the antibody was confirmed by antibody screening at wide thermal range, dithiothreitol treatment of serum and reaction of serum with enzyme treated panel cells.