MMP9 and susceptibility to pneumonia measurement: The top 10 nodes in the network generated by the MNC method were regarded as hub genes (Figure 6A), i.e., IL1B, IL6, CCL2, MMP9, PTGS2, TNF, CRP, EGFR, TLR4, and NOS3. TLR4, TNF, IL1B, and IL6 are also important pneumonia targets.