Much of the earlier work focused on associations of negative affect and depressive symptoms with in-vitro cellular immune function indicators such aslymphocyte proliferative responses (LPR), T-lymphocytehelpertype 1 (Th1) cytokine [interleukin-2 (IL-2) and interferon-gamma (IFN-γ)] production, and natural killer cell cytotoxicity (NKCC) in breast cancer patients (Andersen et al. 1998, Levy et al. 1987). This evidence concerns the gene IFNG and breast cancer.