Surface expression of two low incidence antigens on a single Kell protein. Flow cytometric analysis of 293T cells transiently transfected with the Kell cDNA encoding mutations responsible for K and Js^a antigens (pRc/CMV-K/Js^a). Alloimmune sera used were anti-Js^a (AM), and anti-K (6735416), Js^b (NM), and anti-k (GUE).