CXCR2 and primary ciliary dyskinesia: We detected reduced levels of the chemokine receptors CXCR1 and CXCR2 (Fig. 4A, B) and an increased expression of the chemokine receptor CXCR4 (Fig. 4C) on sputum neutrophils as compared to peripheral blood neutrophils, both in PCD and in bronchiectasis.