PDCD1 and neoplasm: For example, a ‘highly correlated’ anti-PD1 responder (non-core biopsy) containing substantial tumor–stromal interface exhibited correlated high levels of fucosylated HLA-DRB1 and CD4+ T cells, whereas a ‘non-correlated’ responder (a core biopsy) did not (Extended Data Fig. 6d), suggesting that variable stromal content within biopsies may have at least partially undermined the strength of the correlations that we assessed.