ADGRE1 and susceptibility to pneumonia measurement: Notably, among the top 50 differential expressed genes enriched in pneumonia cases several macrophage markers were evident, including the receptor ADGRE1 (murine homolog F4/80) as top-hit, the interleukin-1 receptor-associated kinase-like 2 (IRAK2) or PSTPIP2, which is involved in macrophage polarization (Figure 4E).