Which antibodies are considered naturally occurring?

The antibodies that are considered naturally occurring include those that belong to the ABO blood group system, as well as others like Lewis, P1, MN, and Lua. These antibodies are produced without prior exposure to specific antigens, meaning they often arise in individuals as a result of environmental or microbial antigens rather than from transfusion or pregnancy.

For instance, ABO antibodies (anti-A and anti-B) are typically present in individuals shortly after birth, due to immunological exposure to A and B antigens found in food or gut flora. Similarly, Lewis antibodies develop based on genetic inheritance without the need for sensitization through transfusions or pregnancies. This characteristic of being early responders to antigens makes these antibodies naturally occurring.

In contrast, antibodies such as Rh and Kell are not naturally occurring; they require prior sensitization from blood transfusions, pregnancy, or other exposures to be generated. IgG is a class of antibodies, but it can be both naturally occurring and artificially introduced depending on the context, which doesn’t focus specifically on naturally occurring antibodies. Monospecific anti-human globulin (AHG) is used in laboratory testing to detect sensitized red cells or to enhance agglutination reactions, and it is not relevant to the classification of