CD4 and Arthritis: Our observations of G-MDSC-exos’ ability to suppress the proliferation of CD4+ and CD8+ T cells in vitro and of G-MDSC-exos-treatment-related hematopoietic improvement in the AA/BMF mouse model are consistent with the findings of previous reports showing that G-MDSC-exos treatment reduced the percentages of Th1 and Th17 cells in an arthritis model [17] and suppressed CD4+ T-cell proliferation and Th1-cell response in a colitis model, affirming G-MDSC-exos’ immunosuppressive function [18].