The biochemical nature of the antigens of the P blood group has been well defined. P system antigens are formed by the addition of carbohydrates to the fatty acid chain of sphingolipids. Because of the wide distribution of these antigens in nature, many of the antibodies to P system antigens result from immune response to other organisms. The Donath-Landsteiner antibody, found in cases of paroxysmal cold hemoglobinuria, has been thought to be such a response. Many cases of paroxysmal cold hemoglobinuria (PCH) in children are preceded by a flu-like illness or respiratory infection and are thought to be viral in nature.
In adults, the Donath-Landsteiner antibody may appear in transient association with syphilis. It has been postulated that both the virus and spirochete carried a P-like carbohydrate structure that stimulates the autoantibody production. Recently, another virus, parvovirus B19, has been associated with the P blood group system. In healthy children, parvovirus B19 infection manifests itself with a malar rash while adult infection results in a mild flu-like illness. The persons at greatest risk of developing complications due to B19 are those with sickle cell disease and thalassemia.
The P1 antigen is found in hydatid cyst fluid, and in a considerable variety of worm, both parasitic and free living. It is probably not uncommon that anti-P1 is not infrequently found in the sera of humans in response to worm infestation. The distribution of the p2 allele runs north to south and way from 180 degrees E.
The highest frequencies reported by Blangero for the P2 allele are Circumpolar people, Oriental, and Pacific Islanders, people with a tradition of fish eating, reindeer and caribou hunting/ herding and aquatic mammal diets. Thus the high P2 allele may result from ensuing Helminthiasis?.
- This article is licensed under the GNU Free Documentation License. Sections excerpted from Blood Group Antigen Gene Mutation Database. See: Blumenfeld OO, Patnaik SK. Allelic genes of blood group antigens: a source of human mutations and cSNPs documented in the Blood Group Antigen Gene Mutation Database. Human Mutation. 2004 Jan; 23(1):8-16. PubMed ID: 14695527