This table lists most of the A and B subgroups. Depending on the strength and pattern of RBC agglutination with the typing reagents, A and B groups can be further divided into subgroups. Other criteria such as the presence/absence of unexpected anti-A or anti-B antibodies, as well as the presence/absence of ABH substances in saliva, are also used. A1 occupies the majority of A individuals. Other A subgroups include A2, A3, Ax, and Ael. Similarly, B (B1) occupies the majority of B individuals, and other B subgroups include B3, Bx, and Bel.