PTPRC and graft versus host disease: Based on the above observations and in agreement with the results of ex-vivo analyses, we found that the belimumab therapy group had an increased proportion of mature B cells (B220+IgM+IgD+), as well as a smaller proportion of immature B cells (B220+IgM+IgD−) and memory B cells (B220+IgM−IgD−), than the GVHD experimental group (Figure 4A).