I Blood Group System

• I Blood Group System is an ISBT no. 027 with symbol I
• Ii Collection (under I Blood Group System) has ISBT no. 207 with symbol I
• I Blood Group System has a single antigen: I
• Ii Blood Group Collection has a single antigen: i
• A blood group collection is related to a blood group system, but the genetic basis is not fully resolved
• Adult RBCs are generally I-positive
• Cord RBCs are i-positive
• Cord RBCs are gradually become I-positive over the first 18 months of age.
• I blood group antigens are found on RBC membranes as well as in plasma, milk, and amniotic fluid.
• Anti-I is naturally occurring, cold-reacting IgM antibodies
• Anti-I often detected if tests are done at 4C and may be detected at room temperature
• Anti-I may be pathologic and causative autoantibody in cold agglutinin disease (CAD). CAD may be idiopathic or may be associated with diseases such as Mycoplasma pneumoniae infections
• Anti-I are not associated with HDN
• Anti-IH IgM antibody reacts best at 4C and may be detected at room temperature
• Anti-IH reacts preferentially with adult I-positive cells that express the greatest amount of H antigen (group O)
• Anti-IH usually detected in the serum of A individuals
• Anti-IH may be pathologic and the causative autoantibody in cold agglutinin disease (CAD)
• Anti-i is less common IgM autoantibody that preferentially reacts with iadult red cells and cord red blood cells
• Anti-i reacts optimally at 4C
• Anti-i may be pathologic and the causative autoantibody in cold agglutinin disease (CAD) secondary to infectious mononucleosis; and may cause an associated hemolytic anemia that disappear once the infection is resolved.