A review: low-frequency red cell antigens

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, Js^a) 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.