Fig 1: Neutrophils and other granulocytes were recruited to the lungs within 2 hr of hUC-MSC IV administration. (a) Flow cytometry showed that Cd11c− CD24hi granulocytes and Siglec F− CD11bhi CD103− Ly6Ghi neutrophils increased 2 hr after hUC-MSC injection, and decreased at the 24 hr time point. Kruskal–Wallis test with multiple comparisons; control n = 8, hUC-MSC group n = 4, ∗P < 0.05; ∗∗P < 0.005. (b) MPO+ granulocytes/monocytes (green) clustered around the hUC-MSCs (red) in the lungs 2 hr after cell injection (yellow arrows); their levels decreased at 24 hr. Scale bar = 30 µm. (c) Immunofluorescence quantification of MPO+ cells. Kruskal–Wallis test with multiple comparisons. n = 3, ∗∗P < 0.005; ∗∗∗P < 0.0005. (d) Ly6G + MPO (magenta + cyan) neutrophils surrounded the hUC-MSCs (red) in the lungs 2 hr after cell injection (yellow arrows). 24 hr later, neutrophil numbers had lowered but Ly6G+ cells were still present in the lung. (e) Immunofluorescence quantification of Ly6G+ MPO+ neutrophils. Kruskal–Wallis test with multiple comparisons. n = 3, ∗∗P < 0.005; ∗∗∗P < 0.0005. The number of fields of view counted per condition was 27.