CD74 and infection: Among the signals from macrophages to LZ GC B cells and memory B cells, the Lgals9-Ighm/Cd45 signaling showed a greater enhancement by PCV2 infection, while those signals that were originally stronger in the control group, such as Ptprc-Cd22, Cd52-Siglecg, and App-Cd74, were weaker (Figure 7C,D).