P antigen system

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P antigen system is a human blood group system based upon genes on chromosome 22.

P Antigens[edit]

The P antigens are carbohydrate antigens that include P1, P, and Pk.

P Phenotypes[edit]

P phenotypes are define by reactivity to antibodies to anti-P1, anti-P, anti-Pk and anti-PP1Pk.

  • P1 Phenotype: anti-P1 (+), anti-P (+) and anti-PP1Pk (+) and anti-Pk (-). Seen in 80% of Whites and 95% of Blacks.[1]
  • P2 Phenotype: anti-P1 (-), anti-P (+), antiPP1Pk (+), and anti-Pk (-). Seen in 20% of Whites and 5% of Blacks.[2]
  • Rare p phenotype (absence of P antigens): anti-P1 (-), anti-P (-), anti-PP1Pk (-), and anti-Pk (-). These individuals have a very strong anti-PP1Pk which can be associated with delayed hemolytic transfusion reactions and hemolytic disease of the fetus and newborn (HDFN).[3]

P Antigens[edit]

  • P1, P, Pk and LKE antigens all serve as receptors for P-fimbriated uropathogenic E. coli (cause of chronic urinary tract infections).[10]

P Antibodies[edit]

  • Anti-P1 titers are often elevated in patients with liver flukes (fascioliasis), hydatid cyst disease and who are frequently exposed to birds (which may have P1-like substances in their excrement).[11]
  • Anti-PP1Pk is composed of a mixture of anti-P, anti-P1 and antiPk in the serum of p individuals. Alloanti-P is seen in the sera of P1k and P2k persons and is naturally occurring and predominantly IgM isotype (but may also be a mixture of IgM and IgG).[12] The antibodies are capable of causing hemolytic transfusion reactions and hemolytic disease of the fetus and newborn (if IgG isotype and therefore capable of crossing the placenta).[13] There is a relationship between anti-PP1Pk and early spontaneous abortion (the placenta is rich in Pk and P antigens which are targeted by IgG isotype antibodies).[14]
  • Autoanti-P (Donath-Landsteiner) is an autoantibody of P specificity and is seen in individuals with paroxysmal cold hemoglobinuria (PCH). In PCH, autoanti-P is of IgG isotype and is a biphasic hemolysin (it is capable of hemolysis only after incubation at two different temperatures in vitro). In the body, autoanti-P antibodies bind to red blood cells at cold temperatures (such as in acral circulation) and, after circulating back to the core of the body, subsequently induce intravascular hemolysis in warmer temperatures (core body temperature).[15]

Antibody Detection[edit]

Anti-P antibodies are not usually detected with routine laboratory methods. It is possible to detect them using the Donath-Landsteiner test. This test is performed on 2 vials of blood at two different temperatures: 4 C and 37 C (body temperature). A test is interpreted as positive only after a patient's red blood cells have been incubated at both temperatures and subsequently hemolyzed.[16]

References[edit]

  1. ^ Mais DD. ASCP Quick Compendium of Clinical Pathology, 2nd Ed. Chicago: ASCP Press, 2009.
  2. ^ Mais DD. ASCP Quick Compendium of Clinical Pathology, 2nd Ed. Chicago: ASCP Press, 2009.
  3. ^ Mais DD. ASCP Quick Compendium of Clinical Pathology, 2nd Ed. Chicago: ASCP Press, 2009.
  4. ^ Roback JD et al. AABB Technical Manual, 16th Ed. Bethesda: AABB Press, 2008.
  5. ^ Cooling LW, Walker KE, Gille T, Koerner TAW. Shiga Toxin Binds Human Platelets Via Globotriaoslyceramide (Pk antigen) and a Novel Platelet Glycosphingolipid. Infect Immun 1998; 66: 4355-66.
  6. ^ Beadling W, Cooling L. Immunohematology. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 25th Ed. Philadelphia: Saunders, 2007: 618-68.
  7. ^ Spitalnik PF, Spitalnik SL. The P Blood Group System: Biochemical, Serological, and Clinical Aspects. Transfus Med Rev 1995; 9: 110-22.
  8. ^ Roback JD et al. AABB Technical Manual, 16th Ed. Bethesda: AABB Press, 2008.
  9. ^ Roback JD et al. AABB Technical Manual, 16th Ed. Bethesda: AABB Press, 2008.
  10. ^ Roback JD et al. AABB Technical Manual, 16th Ed. Bethesda: AABB Press, 2008.
  11. ^ Roback JD et al. AABB Technical Manual, 16th Ed. Bethesda: AABB Press, 2008.
  12. ^ Roback JD et al. AABB Technical Manual, 16th Ed. Bethesda: AABB Press, 2008.
  13. ^ Roback JD et al. AABB Technical Manual, 16th Ed. Bethesda: AABB Press, 2008.
  14. ^ Roback JD et al. AABB Technical Manual, 16th Ed. Bethesda: AABB Press, 2008.
  15. ^ Roback JD et al. AABB Technical Manual, 16th Ed. Bethesda: AABB Press, 2008.
  16. ^ Mais DD. ASCP Quick Compendium of Clinical Pathology, 2nd Ed. Chicago: ASCP Press, 2009.

Dr.Purabolicur

Reference MR YU FROM GLADSTONE SECONDARY

External links[edit]

  • P at BGMUT Blood Group Antigen Gene Mutation Database at NCBI, NIH