What is the significance of the I/i antigen in the context of cold agglutinin disease?

A It is an autoantigen that reacts with cold agglutinins ✓
B It is an alloantigen that reacts with warm autoantibodies
C It is a cryptantigen that is only expressed at low temperatures
D It is a neutral antigen that does not react with any antibodies

Explanation

The I/i antigen is an autoantigen that reacts with cold agglutinins, which are autoantibodies that bind to red blood cells at low temperatures, leading to hemolysis.

Source

Clinical Hematology Atlas
Hematology Hematology: Blood Grouping and Crossmatching Hematology: Blood Grouping and Crossmatching Medium MEDICAL Confidence: medium