Erythrocyte Blood Group Antigenic Systems : Kell/Cellano System
المؤلف:
Marcello Ciaccio
المصدر:
Clinical and Laboratory Medicine Textbook 2021
الجزء والصفحة:
p204-205
2025-07-23
588
Antigens: The major antigens of the system are the Kell (K) antigen present in 9% of Caucasians and 2% of blacks, and the cell (k) antigen present in over 99% of individuals. Other antigens of the Kell system, antithetical to each other, are Kpa/Kpb, and Kpc; Jsa/Jsb; K11/K17; K14/K24. An ethnic distribution is also observed for the Kpa and Jsa antigens, as Kpa is mainly observed in white subjects while Jsa is predominantly detected in subjects of African origin. Also described are subjects totally devoid of anti gens referable to the Kell blood group system, defined as Ko or Knull. The antigens of the Kell system are located on a 93-kD transmembrane protein rich in cysteine and capable of forming sulfhydryl bonds. They are, therefore, conformational antigens, sensitive to the treatment of red blood cells with agents capable of altering the secondary structure of the molecule (mercaptoethanol, for example). It appears that this protein belongs to the family of neutral endopeptidases, which act as a bond for Zn; it also has a high similarity with the common antigen of lymphoblastic leukaemia (CALLA or CD10). Although the Kell system locus is located on chromosome 7 and the Kx (XK) locus is located on the X chromosome, it appears that the K and Kx proteins form a covalent complex on the surface of the red cells. The lack of Kx antigen is accompanied not only by a weak expression of the Kell antigens, but also by acanthocytosis and reduced erythrocyte survival. These erythrocyte abnormalities can be accompanied by an increase in the creatine kinase (CK) enzyme and neuro muscular abnormalities, constituting the so-called McLeod phenotype, probably linked to abnormalities of the XK locus.
Antibodies: The K antigen is highly immunogenic. Anti-K antibodies are, therefore, frequently detected in the serum of transfused kk patients, although anti-K have rarely been observed even in subjects never exposed to nonself erythrocytes. These are IgG class immunoglobulins, with an optimum temperature at 37 °C, reactive with the antiglobulin test. Being able to generate PTH and HDFN, they are considered clinically significant antibodies. The k antigen is also highly immunogenic, as it can generate the appearance of IgG-class allo-antibodies, with an optimum temperature of 37 °C, reactive with the antiglobulin test. Being able to generate PTH and HDFN, they are also considered clinically significant. Anti-Kpa, anti-Kpb, Anti-Jsa, and anti-Jsb anti bodies are all much less frequent than anti-K, but have simi lar serological characteristics, and are therefore to be considered clinically significant.
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