CD8A and lymphopenia: Alternatively, naïve CD8 T cells may undergo proliferation in the absence of antigen under conditions of lymphopenia (abnormally low level of lymphocytes in the blood) in response to self-antigen-MHC, interleukin-7 (IL-7), and/or IL-15 [97] The antigen-independent proliferation of naïve CD8 T cells is defined as homeostatic proliferation, and it plays an important role in maintaining normal CD8 T cell numbers.