Kidd System

The Kidd system is represented by the common alleles Jka and Jkb. The frequency of Jka in the Caucasian population is 77%, which is similar to Jkb at 74%. Amongst Black individuals, however, Jka is much more prevalent than Jkb (92% vs 49%).

Antibodies directed against Kidd antigens have been associated with severe hemolytic transfusion reactions partly due to their evanescent nature and potential to fix complement. Titers of anti-Kidd antibodies can rapidly fall to undetectable levels within a few months making it difficult to detect and easy to miss during routine testing.

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