The recognition of DQB1*0303 by DQ9 and or DQ3 is poorest, DQ2 which recognizes a different DQB1 subgroup recognizes DQB1*0303 as efficiently as DQ3.
HLA-DQ3 (DQ3) is a broad serotype category with split antigens HLA-DQ7, DQ8, and DQ9.
DQ7 is a form of 'split antigen' of the broad antigen group DQ3 which also contains DQ8 and DQ9.