CD74 and infection: Figure 3a–c shows the top nine differential genes highly expressed by macrophages in three groups of specimens, and by comparing the marker genes of macrophages in different treatment groups, it can be inferred that the cell function changes caused by different stimuli or treatments. Combining Figure 4 with the clustering heatmap, it can be seen that the model group has a higher expression of complement C1qa, CD74 molecule, Lgmn, etc., compared to the normal group; after PDT treatment in the infection model, the genes C1qc, F13a1, Ctss, Mrc1, etc., were upregulated.