Fig. 4.

Amino-acid variation plot for a DQB and b DRB alleles. Human antigen-binding sites (ABS) are indicated with the letter ‘h’, whereas positively selected sites (PSS) are indicated with black triangles. In the DRB plot there are no amino acids between the positions 24–25, because these alleles were only 163 bp long, whereas 19 DQB alleles were 169 bp long, with an insertion of two codons at positions 24–25