Related Experiment Video
Updated: Jun 17, 2026
Identification of Mouse and Human Antibody Repertoires by Next-Generation Sequencing
Published on: March 15, 2019
Anti-M: Report of two cases and review of literature
Rashmi Tondon1, Rahul Kataria, Rajendra Chaudhry
1Department of Transfusion Medicine, Sanjay Gandhi Post Graduate Institute of Medical Sciences, Rae Bareily Road, Lucknow, Uttar Pradesh, India.
Abstract:
Anti-M is a fairly common naturally occurring antibody with rarely causing hemolytic transfusion reactions or hemolytic disease of the newborn. Most anti-M are not active at 37 degrees C and can generally be ignored in transfusion practice. However, we did not find this antibody to be fairly common and detected only two cases of anti-M in the past three years. We describe these two cases; one 'immunizing' type and other 'naturally occurring' and review the literature. The immunizing type was reactive at 37 degrees C as well as AHG phase of testing with IgG component, and showing dosage effect while the other was 'naturally occurring' reactive well below 37 degrees C. Though rare, sometimes these antibodies can be of clinical significance when the antibody detected is reactive at 37 degrees C and AHG phase. When the antibody is active at 37 degrees C, M antigen negative cross match compatible red cell unit should be given.
Insights
Anti-M antibodies are rare and can cause transfusion reactions. Immunizing anti-M is clinically significant, requiring M antigen-negative blood transfusions for patient safety.
Area of Science:
- Transfusion Medicine
- Immunology
- Blood Banking
Background:
- Anti-M antibodies are typically considered common and clinically insignificant in transfusion practices.
- Most anti-M antibodies are not reactive at 37°C, minimizing transfusion risks.
Observation:
- This study identified only two cases of anti-M over three years, contradicting its common prevalence.
- One case presented as an 'immunizing' type, reactive at 37°C and AHG phase with IgG and dosage effects.
- The second case was a 'naturally occurring' type, reactive below 37°C.
Findings:
- The immunizing anti-M variant demonstrated significant reactivity at body temperature and via the antiglobulin phase.
- Naturally occurring anti-M showed reactivity only at lower temperatures.
Implications:
- Rarely, anti-M antibodies can be clinically significant, particularly when reactive at 37°C and the AHG phase.
- Patients with clinically significant anti-M require transfusions with M antigen-negative red blood cells to prevent hemolytic reactions.
