User talk:73.110.37.88

WRT, see under "Antibodies" ("The antibodies of the ABO system are "naturally occurring" in that they are formed as a result of exposure to ABH-like substances from the gastrointestinal tract, occurring in utero or immediately postpartum and peaking about 5 to 10 years of age.") - Nunh-huh 13:54, 2 February 2018 (UTC)