Final answer:
Antigens from individuals of the same species are less immunogenic compared to those from distant species because of genetic similarities. The immune system more readily identifies as 'nonself' the antigens from a different species due to significant molecular differences. In situations like bone marrow transplantation, it is critical that donor and recipient HLAs match to prevent immune rejection.
Step-by-step explanation:
Antigens from individuals of the same species are less immunogenic than those from more distant species due to the genetic similarities among individuals of the same species. The concept of antigenicity relates closely to the immune system's ability to recognize and respond to foreign antigens. When an individual is exposed to an antigen from a very different species, the immune system recognizes it as 'nonself' more readily because of the significant differences in molecular structures.
Furthermore, factors such as molecular complexity, size, and epitope structure affect an antigen's immunogenicity. The adaptive immune system identifies specific pathogens through antigens on their surface and generates responses tailored to the specific pathogen. The greater the genetic difference between the species of the donor and recipient of antigens, the more immunogenic the antigens tend to be.
In the case of a bone marrow transplant, a good match must exist between a donor and recipient in terms of human leukocyte antigen (HLA) proteins to prevent immune rejection. If a donor's HLAs are different from the recipient's, the immune system's antibodies will perceive the donor's antigens as foreign and mount an attack, leading to transplant rejection.