The Côté serum (anti-K11), an antibody defining a new variant in the Kell system

The serum from a 50-year-old woman, Mrs. Côté, was found to agglutinate all cell samples except her own, those of two siblings, and Ko erythrocytes. Her Kell phenotype is a common: K-k+, Kp(a-b+), Js(a-b+), Ul(a-), K:12, K:13, K:14, K:18. Anti-K11 present in her serum defines a high-frequency red cell antig