A transiently occurring anti-Kell (K1) antibody was observed in a 4-year-old girl who had acute lymphocytic leukemia and upper respiratory tract infection. The patient had nerve received a blood transfusion. Testing with dithiothreitol and anti-immunoglobulin-coated bead (Immunobead_??_) showed the antibody to be IgM class. The “naturally-occuring” antibody was demonstrated for 5 weeks, disappeared from the serum at 9th week after the first detection and never detected for 79 weeks afterward.
