Background and aims Plasmacytoid dendritic cells (pDC) are potent producers of IFNα, we investigated what additional soluble factors are produced by pDCs and the effect of pDC depletion with JNJ-56022473 (JNJ-473), a novel antibody against CD123. We then investigated which of these factors are elevated in SLE patient sera to determine potential biomarkers.
Methods pDCs were isolated from healthy donor (HD) PBMC (n=6) which were stimulated with CpGc (TLR9) and imiquimod (TLR7) then analysed by RNAseq. PBMC from SLE and HD were also treated with isotype or JNJ-473 before stimulation with CpGc for 24 hour. Culture supernatant, SLE (n=33) and HD sera (n=34) was analysed by bead-based multiplex assay (Myriad U.S.A).
Results TLR9 and TLR7-agonism induced the regulation of thousands of genes, many of which were different IFNα-subtypes. Transcripts of many other secreted proteins such as MCP-2/CCL8, IP-10/CXCL10, ITAC/CXCL11 and MIP-3β/CCL19 were also upregulated. Proteins of these were also found to be significantly increased in SLE sera compared to HD.
Depleting pDCs with JNJ-473 in SLE and HD PBMC cultures reduced production of many CpGc-induced proteins including IFNα, MCP-2/CCL8, IP-10/CXCL10, ITAC/CXCL11 and MIP-3β/CCL19. RNAseq of SLE PBMC treated with JNJ-473 before CpGc stimulation, confirmed significantly decreased expression of MCP-2/CCL8, IP-10/CXCL10 and ITAC/CXCL11.
Conclusions We found that pDC depletion with JNJ-473 was able to prevent TLR9-induced production of IFNα and various other soluble proteins which are elevated in the sera of SLE patients. We propose that these soluble factors could be useful biomarkers to determine the effectiveness of pDC depletion and the modulation of IFN in SLE.
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