The results of LTEM assays with neutrophils manipulated. (a,b) Clinically freshly isolated neutrophils were left untreated or treated with S100A12, followed by LTEM assays. Compared with the control, S100A12 treatment allowed more neutrophils to penetrate the endothelial layer (2,857 vs. 2,051). (c) By three independent assays, S100A12 treatment significantly promoted freshly isolated neutrophils (donated by a healthy male adult) to infiltrate and to migrate through the endothelial layer. (d) KD serum promoted neutrophils (cell line) infiltration by approximately 1.7-fold, which allowed us to mimic KD disease by using serum treatment (n = 3). (e) KD serum-treated neutrophils (cell line) were simultaneously treated with a control IgG, S100A12 antibody or IVIG, followed by LTEM assays (n = 3). Data were presented as the mean ± SD. *, **, *** and **** denoted p-values < 0.05, 0.01, 0.001 and 0.0001 according to t-tests, respectively.