CSF2 and chronic obstructive pulmonary disease: AD, atopic dermatitis; CBA, cytometric bead array; CF, cystic fibrosis; COPD, chronic obstructive pulmonary disease; ELISA, enzyme‐linked immunosorbent assay; GM‐CSF, granulocyte‐macrophage colony‐stimulating factor; IFNγ, interferon gamma; IL, interleukin; PF, pulmonary fibrosis; PGD2, prostaglandin D2; scRNAseq, single cell RNA sequencing; TGFβ, transforming growth factor beta.