IL-28A targets neutrophils. Levels of pSTAT1 in Percoll-purified neutrophils from bone marrow (a) and total bone marrow (b) stimulated with IL-28A or IFN-β in vitro for 15 or 30 min. A representative of four independent experiments is shown. (c) mRNA levels of IL-28RA in a neutrophil enriched population of cells from mouse arthritic joints (CD11b⁺ nonadherent) compared with macrophages (CD11b⁺ adherent) and total cells isolated from the joint (all cells). Statistical analysis was performed by one-tailed Mann-Whitney U test.