ARG1 and graft versus host disease: Furthermore, the use of ARG1 KO donors in mouse BMT models, when combined with high fat-induced inflammatory conditions (i.e., a Western diet), leads to a decrease in circulating B cells and spleen size (34), suggesting that a reduction in ARG1 expression in GGF patients may prime them for the development of PGF upon a further subsequent injury to the BM such as infection or GVHD.