Fig. 4. Potential immunotherapeutic approach to sepsis. Two novel approaches to sepsis include use of the immunomodulatory molecules IL-7 and anti–PD-1. IL-7 acts on CD4 and CD8 T cells to block sepsis-induced apoptosis and to cause cell proliferation. IL-7 also enables CD4 and CD8 T cells to respond to the pathogens and produce important cytokines, such as interferon-γ, which activate macrophages. IL-7 also improves the ability of lymphocytes to traffic to the site of infection, thereby assisting in pathogen killing. Anti–PD-1 antibody is able to act on CD4 and CD8 T cells that have become inactivated or “exhausted” to restore their ability to respond to the infection. The activated lymphocytes are able to produce interferon-γ to assist in pathogen killing. IL-7 = interleukin 7; IL-7R = interleukin 7 receptor; IFN-γ = interferon-gamma; PMN = polymorphonuclear leukocyte; PD-1 = programmed cell death 1.