Typically, we only don't have antibodies for self-antigens. If we do encounter them, then the cells that produce those antibodies will multiply and the number of those antibodies will greatly grow. In conclusion, we can and do have antibodies for more antigens than we will ever encounter, and we have then before ever encountering them. Likewise, someone with an O type blood won't have both the A and B antigens, and so cells producing antibodies that bind to them will be allowed to mature, and they will have anti-A and anti-B antibodies circulating in the blood. Organisms with the A antigen will present it to maturing lymphocytes and thus create tolerance to it, not having cells producing A-antigen binding antibodies but they don't have the B antigen, so their lymphocytes won't be selected over it, and they will have cells producing B-antigen binding antibodies, which, if such antigen is introduced into the body, will mount an immune response against it. In this process, specialized cells present a myriad of self-antigens to the maturing lymphocytes, signalizing them to undergo apoptosis or become regulatory cells if they bind to them. Bethesda, Md.: NCBI.Īntibody-producing cells (B lymphocytes) generate antibodies through a gene recombination process, that allows a virtually infinite number of antibodies to different antigens to be created, including against self-antigens ( (D)J_recombination).Ī process of maturation, if working correctly, allows for those cells producing antibodies that strongly bind to self-antigens to be suppressed or eliminated, preventing autoimmune attacks ( ). People with type AB blood: they won't produce antibodies (regarding A and B antigens).People with type O blood: they will produce anti-B and anti-B antibodies. Blood group O (or blood group zero in some countries) individuals do not have either A or B antigens on the surface of their RBCs, but their blood serum contains IgM anti-A antibodies and anti-B.People with type B blood: they will produce anti-A antibodies. People with type A blood: they will produce anti-B antibodies.As we get in contacts with antigens A and B, this is what happens: Thus, from an early age, we have contact with the antigens, coming from food or bacteria in our digestive system. This happens at an early age because sugars that are identical to, or very similar to, the ABO blood group antigens are found throughout nature. Their production is stimulated when the immune system encounters the "missing" ABO blood group antigens in foods or in micro-organisms. The answer is: there was contact with the antigens, even without a blood transfusion.Īccording to Laura Dean ( Blood Groups and Red Cell Antigens, chapter 5):ĪBO antibodies in the serum are formed naturally. That being said, how it's possible a type O individual producing anti-A and anti-B antibodies without having any contact with the antigens? And that is the same as asking "how it's possible a type A individual producing anti-B antibodies without having any contact with the antigen?" To understand what's happening here, let's have a look at the actual ABH (or ABO) antigens:Īs you can see, they are not very big molecules: quite the opposite, they are relatively small globosides.
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