Interestingly, studies that compared tumours infiltrated by leukocytes (‘hot’) to those that excluded immune cell infiltration (‘cold’) identified more abundant CCL3, CCL4, and CCL5 in hot tumours (Chakravarthy et al., 2018; Spranger et al., 2015), including via single-cell transcriptomics that ascribed their expression to CD8+ T cells (Jerby-Arnon et al., 2018; Roider et al., 2020). The gene discussed is CCL5; the disease is neoplasm.