In single-cell secreting proteomics of SF-derived Treg cells in CBIA patients, we found that clusters distinct to the immunoactivating cell group featured inflammatory cytokine secretion of mainly MCP1 and MCP4, which was validated by peripheral CBIA secreting proteomics (vs. RA, which preferentially secreted CCL11/CXCL10). Here, CCL13 is linked to rheumatoid arthritis.