Intriguingly, PPBP (CXCL7) and PF4 (CXCL4) belong to the CXC chemokine family, which plays a pivotal role in the development or progression of rheumatoid arthritis (RA), antiphospholipid syndrome, and systemic lupus erythematosus (53, 54). Here, PF4 is linked to systemic lupus erythematosus.