To construct a humanized mouse model of systemic lupus erythematosus (SLE) that resembles the human disease in order to define the pathophysiology and targets for treatments.

We infused peripheral blood mononuclear cells (PBMCs) from SLE patients into BALB‐ RAG‐2^−/−IL‐2Rγ^−/− double‐knockout (DKO) mice, which lack T cells, B cells, and natural killer cells. PBMCs from 5 SLE patients and 4 normal donors were infused intravenously/intraperitoneally at a density of 3–5 × 10⁶ cells per animal into nonirradiated 4–5‐week‐old mice. We evaluated the engraftment of human CD45+ cells and monitored the plasma levels of human IgG, anti–double‐stranded DNA (anti‐dsDNA) antibody, and anticardiolipin antibody (aCL), as well as proteinuria and kidney histology.

There was 100% successful engraftment in 40 DKO mice infused with human PBMCs. In the PBMC fraction from SLE PBMC–infused DKO (SLE‐DKO) mice and normal donor PBMC–infused DKO (ND‐DKO) mice, an average of 41% and 53% human CD45+ cells, respectively, were observed at 4 weeks postengraftment, with 70–90% CD3+ cells. There were fewer CD3+CD4+ cells (mean ± SEM 5.5 ± 2.1%) and more CD3+CD8+ cells (79.4 ± 3.6%) in the SLE‐DKO mice as in the SLE patients from which the PBMCs were derived. CD19+ B cells and CD11c+ monocytic cells were found in the spleen, lung, liver, and bone marrow. There was no significant difference in plasma levels of human IgG and anti‐dsDNA antibodies between SLE‐DKO and ND‐DKO mice. Levels of aCL were significantly higher in all SLE‐DKO mice infused with PBMCs from an SLE patient who had high titers of aCL. SLE‐DKO mice had proteinuria, human IgG deposits in the kidneys, and a shorter life span. In SLE‐DKO mice engrafted with PBMCs from the aCL‐positive patient, we found microthrombi and infiltration of CD3+, CD8+, and CD19+ cells in the glomeruli, recapitulating the human antiphospholipid syndrome in these mice.

We established a novel humanized SLE‐DKO mouse exhibiting many of the immunologic and clinical features of human SLE.