An algorithm for nonpermissive HLA-DPB1 disparities according to TCE3 or TCE4. (A) HLA-DPB1 alleles were classified into 3 groups (TCE3), or 4 groups (TCE4), on the basis of T-cell alloreactivity. TCE3 group 1 and TCE4 group 1: Alleles encoding antigens recognized by all T-cell clones studied by Zino et al.¹¹  TCE3 group 2 and TCE4 group 2: Alleles encoding antigens recognized by some but not all T-cell clones studied by Zino et al.¹¹  TCE 3 group 3: Alleles encoding antigens recognized by none of the T-cell clones studied by Zino et al.¹¹  “Others” refers to all alleles that can be classified according to the algorithm of Zino et al.²⁰  TCE4 group 3: DPB1*02, encoding antigens eliciting intermediate levels of MLR reactivity.^13,14,21  TCE4 group 4: All alleles from TCE3 group 3 except for DPB1*02. (B) The 3 or 4 groups of HLA-DPB1 alleles can be present in different combinations in diploid cells. Numbers indicate the group of the first (before the slash) and the second (after the slash) HLA-DPB1 allele of donor or recipient. Classification of HLA-DPB1 group disparities as permissive or nonpermissive in GvH or HvG direction is indicated for all possible combinations. Note that all nonpermissive TCE3 disparities are also TCE4-nonpermissive (gray boxes). In contrast, only a part of the TCE3-permissive disparities are permissive also according to TCE4 (white boxes), whereas the remaining TCE3-permissive disparities score as nonpermissive in TCE4 (striped boxes).