Are we born with circulating antibodies or are they synthesized upon exposure to non-self antigens?
The ‘naturally occurring’ antibodies of the majority of group A or B individuals are mainly IgM and produced in response to environmental ABO antigens, e.g. from microbes in the gut and respiratory tract.
Most of the group O adults, and a small proportion of group A and B subjects, have naturally occurring, usually weak, IgG in addition to stronger IgM ABO antibodies.
The cord blood usually does not contain ABO antibodies although maternally derived IgG anti-A or -B can sometimes be detected.
However. the newborn infants do not produce ABO antibodies until the 3rd-6th month of age .
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The AB0 blood groups ( https://www.ncbi.nlm.nih.gov/books/NBK2267/ ) are characterised by the type of carbohydrates attached to glycolipids and glycoproteins attached by glycosyl-transferases: The ABO locus has three main alleleic forms: A, B, and O. The A allele encodes a glycosyltransferase that produces the A antigen (N-acetylgalactosamine is its immunodominant sugar), and the B allele encodes a glycosyltransferase that creates the B antigen (D-galactose is its immunodominant sugar). Similar glycosylations being present in food and microorganisms stimulate the production of IgM antibodies against those antigens not expressed by the individual's cells, therefore these antibodies are constitutionally present. IgM's are not transported across the placenta into the foetus, therefore the AB0 system is not a problem during pregnancy.
In contrast, the antigens of the Rh blood group system (Article The Rh blood group system: A review
) are proteins capable of stimulating an IgG response upon exposure, e.g. while giving birth. IgG antibodies get transferred from the mother to the foetus, therefore they can present a problem in subsequent pregnancies
Annemarie Honegger Shail K Chaube What would be the possibility to get high antibody whent here is a mixing of blood between unrelated people. most precesily when there is a organ donation between unrelated donor vs acceptor?. My understading is that the antibody against the donor blood will present in the recepient blood only of the donor is having any blood relationship with the recepient.
They are naturally occurring antibodies in our body from birth. The blood group of a particular person has antigens and antibodies for their corresponding blood groups from birth itself.
circulating antibodies are synthesized following exposure to nonself antigens.
Nikhil Maroli, as mentioned above, the AB0 antigens are carbohydrate groups attached to glycosylated proteins and determined by the enzymes that are responsible for this glycosylation. The same carbohydrate groups are present in foods and microorganisms in your gut - you therefore are exposed to all of them from earliest childhood, and produce antibodies to all except the ones your own cells express, which are suppressed as self antigens.
If you get blood from a donor with an incompatible AB0 blood group, the antibodies already present in your own blood will attack the erythrocytes in the foreign blood, leading to their destruction, and antibodies in the foreign blood will attack an lyse your own erythrocytes.
If you get another organ from a donor with an incompatible AB0 blood group, the antibodies already present in your own blood will attack these antigens on the surface of the cells of the donated organ.
Ongoing research studies the possibility to remove the offending carbohydrate antigens by treatment with glycosidases ( Article Toward universal donor blood: Enzymatic conversion of A and ...
)."My understading is that the antibody against the donor blood will present in the recepient blood only of the donor is having any blood relationship with the recepient." This understanding is false. If donor and acceptor are closely related, the probability is higher that they carry the same antigens and therefore are compatible.
However, besides antibodies, the HLA(MHC)/T-Cell system is also of importance for histocompatibility.
Annemarie Honegger Thanks for the explanation. I am going to have kidney transplant in couple of months from an unrelated donor. The HLA and donor specific antibodies are found to be low reactivity, hence identified as suitable donor.
Blood group antibodies may develop naturally or may develop as a result of exposure to foreign RBC antigens during, after previous transfusions or transplants, or as a result of contact with fetal RBCs during or after gestation. According to Shy et al. 2019, the patient's plasma is combined with two or three reagent RBCs of known phenotype that were obtained from donors of type O for the Ab screen in order to prevent interference from naturally existing anti-A or anti-B Abs. This test tries to determine whether the Ab found in the patient's plasma is specific for key RBC Ags and may have clinical relevance.
References:
Gandhi, M. J., Strong, D. M., Whitaker, B. I., & Petrisli, E. (2018). A brief overview of clinical significance of blood group antibodies. Immunohematology, 34(1), 4–6. https://doi.org/10.21307/immunohematology-2018-002
Shy, B. R., Tholpady, A., & Nedelcu, E. G. (2019). Interferences in blood bank testing. In Accurate Results in the Clinical Laboratory (pp. 425-437). Elsevier. DOI: 10.1016/B978-0-12-813776-5.00028-5
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