Question: what is the difference between the groups a1 and a2 on a routine blood grouping?
Answer: A1 and A2 are distinguished by the reactivity of lectin i.e., anti-A1 which occurs as a cold agglutinin and exclusively agglutinates A1 cells. About 0.4% A2 and 25% of A2B subgroups possess anti-A1. These antibodies become clinically significant if they react at 37°C destroying A1 cells [2].