Warm IgM anti-IT causing autoimmune haemolytic anaemia

Area of Science:

• Immunology
• Hematology
• Serology

Background:

• Autoimmune hemolytic anemia (AIHA) is characterized by autoantibodies targeting red blood cells.
• Autoagglutinins, particularly those with specificities like anti-I or anti-IT, can cause complex serological findings.
• Understanding antibody characteristics is crucial for accurate diagnosis and management of AIHA.

Observation:

• A patient presented with AIHA involving an autoagglutinin of anti-IT specificity.
• The autoantibody was identified as IgM class and complement-binding.
• A notable observation was the antibody's optimal reactivity at 37°C, which is atypical for many cold-reacting autoantibodies.

Findings:

• A prozone phenomenon was observed in serum testing but absent in eluate testing.
• Investigations indicated the prozone was caused by a high-molecular-weight blocking antibody.
• This blocking antibody demonstrated specificity for both I and IT antigens.

Implications:

• This case highlights the diverse nature of autoantibodies in AIHA.
• The presence of a high-molecular-weight blocking antibody can complicate serological interpretation.
• Accurate identification of antibody specificity and behavior is essential for effective patient management in transfusion medicine.