Fig. 2: Assessment of HLA-I expression type.

a HLA-I expression type was assessed by expression patterns of HLA-ABC, β2-microglobulin (B2M), HLA-A, HLA-B and HLA-C immunohistochemistry. First, the case showing expression loss of HLA-ABC and B2M was classified as the HLA-I total loss type. In the second stage, the HLA-ABC/B2M-positive group was sub-classified according to their reactivities to HLA-A, HLA-B and HLA-C. If a case showed expression loss of HLA-A, HLA-B or HLA-C, it was considered as the HLA-I locus loss type. No expression loss of HLA-I or its subunit was classified as HLA-I intact type. b Representative immunohistochemistry results of the HLA-I total and locus loss types (HLA-A locus loss) (×100). The yellow arrowhead indicates the expression loss of HLA-A in tumour cells.