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

. The serum from a 50-year-old woman, Mrs. Cote, was found to agglutinate all cell samples except her own, those of two siblings, and Ko erythrocytes. Her Kell phenotype is a common one: 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 antigen that is related to the Kell system.