The results showed that PSGL1lo and PSGL1hi CD4+ memory T cells preferentially migrated back to the original GVHD target tissues in the adoptive recipients, but only PSGL1loCD4+ T cells augmented expansion of plasma cells in the GVHD target tissues and increased serum concentration of total IgG and anti-dsDNA-IgG in a manner that required PD-1 interaction with PD-L2 (47). Here, CD4 is linked to graft versus host disease.