CTLA4 and lymphopenia: Accordingly, patients with immune disorder indicated by persistently low mHLA-DR expression may benefit from immunostimulatory therapies like GM-CSF or IFN-γ; for persistent lymphocytopenia caused by large-scale lymphocyte apoptosis, IL-7 therapy can effectively restore T cell count and function; and for the exhausted phenotype characterized by high PD-1/CTLA-4 expression on T cells, the use of immune checkpoint inhibitors during a defined immunosuppressive period can restore T cell function.