After the incubation of isolated neutrophils with sera from TP without pneumonia, CD62L expression on neutrophils was significantly decreased at each study period compared to the corresponding samples from TP with pneumonia or ctrl (ED: 7.49 ± 1.07 MFU vs. 19.50 ± 3.19 MFU, one day prior infection: 11.52 ± 2.47 MFU vs. 25.67 ± 3.16 MFU, and day of infection: 12.74 ± 2.83 MFU vs. 30.19 ± 5.70 MFU, respectively, and ctrl: 23.73 ± 3.26 MFU, all p < 0.05, Fig. 3). Here, SELL is linked to susceptibility to pneumonia measurement.