Fig. 3.

Serum granulocyte–macrophage colony-stimulating factor (GM-CSF) autoantibody concentration and neutrophil bacterial killing. The frequency of Staphyloccus aureus killing by isolated adherent peripheral blood neutrophils and the neutrophil CD64 activation index were determined by flow cytometry and serum GM-CSF autoantibody concentration was determined by enzyme-linked immunosorbent assay (ELISA). The association between serum GM-CSF autoantibody concentration and neutrophil bacterial killing was tested by Spearman's correlation in (a) the entire Crohn disease (CD) cohort, n = 44 or (e) the CD patients with neutrophil CD64 activation index in the normal range, <1·3, n = 25. Neutrophil bacterial killing is shown in (b) for the entire CD cohort stratified by serum GM-CSF autoantibody concentration of 1 μg/ml and (f) the CD patients with neutrophil CD64 activation index in the normal range, <1·3, stratified by serum GM-CSF autoantibody concentration of 1 μg/ml. Differences between groups were tested by Mann–Whitney U-test. (c) The association between neutrophil CD64 activation index and bacterial killing was tested by Spearman's correlation, n = 44. (d) Neutrophil bacterial killing is shown for the entire CD cohort stratified by CD64 activation index of 1·3. Differences between groups were tested by unpaired t-test. *P < 0·05; **P < 0·01; ***P < 0·001.