IgG4 antibodies have naturally reduced affinities for most FcγRs and C1q (Crescioli et al., 2016; Jiang et al., 2011) but still retain high affinity to FcγRI and binding to FcγRIIb, which can result in macrophage‐mediated phagocytosis of PD‐1‐positive T cells (Arlauckas et al., 2017) and decreased anti‐tumour activities. Here, PDCD1 is linked to neoplasm.