We then used the I-Abm12 chronic graft-versus-host-disease (cGvHD) mouse model, in which an allogeneic interaction of T and B cells expressing different major histocompatibility complex (MHC) class II (I-A) induces an SLE-like phenotype.37 38 As shown in figure 5A, Tnfsf4−/− and Tnfsf4fl/fl(CD19)−/− mice injected with B6.H2-Ab1bm12 splenocytes developed a lower titre of IgG anti-dsDNA compared with controls. This evidence concerns the gene CD19 and systemic lupus erythematosus.