C5AR1 and systemic lupus erythematosus: In fact, the critical role of the C5a signaling pathway in mediating NPSLE via neutrophil infiltration was evident in an experimental study that demonstrated reduced cerebral neutrophil infiltration, neuronal apoptosis and expressions of p-JNK, pSTAT1 and p-ERK after treatment with C5a receptor antagonist in MRL/lpr lupus-prone mice (161).