Abstract
The study of low-frequency red cell antigens and their corresponding antibodies is an eccentricity in immunohematology. Quite often, antigens that have very low frequencies in one population are not that infrequent in another;1 e.g., the antigens Mur, Hut, and Hil of the MilII phenotype. In addition, “low-frequency” antigens (LFAs) of one ethnic group (e.g., K, Jsa) can have an appreciable incidence in another ethnic group within the same population. Hence, there is no rigid definition as to what constitutes a LFA. Antibodies to LFAs, most of which have little, if any, clinical significance, are most often encountered in autoimmune and hyperimmune states.2 Nevertheless, despite their general clinical irrelevance, LFAs and their antibodies still exert a strong fascination for many red cell serologists.