“…The evidence includes the following: (1) increased numbers of peripheral blood mononuclear cells (PBMC), such as neutrophils, monocytes, and activated T lymphocytes (Herbert and Cohen 1993;Maes et al 1992Maes et al , 1993cMuller et al 1993;Sluzewska et al 1996aSluzewska et al , 1996bSeidel et al 1996b;Perini et al 1995); (2) increased secretion of neopterin, a sensitive marker of cell-mediated immunity (Duch et al 1984;Dunbar et al 1992;Maes et al 1994;Bonaccorso et al 1997); (3) increased secretion of prostaglandin E2 (PGE2) in serum, CSF or culture supernatant obtained after polyclonal stimulation of whole blood (Linnoila et al 1983;Calabrese et al 1986;Song et al submitted;and (4) the presence of a moderate acute phase response, as indicated by increased serum concentrations of positive acute phase reactants, such as haptoglobin, C-reactive protein, and ␣ 1-antitrypsin (Maes et al 1993b(Maes et al , 1995b(Maes et al , 1997aJoyce et al 1992;Sluzewska et al 1996a) and decreased serum concentrations of negative acute phase reactants, such as albumin, transferrin, and zinc (Swartz 1990;Maes 1997;McLoughlin and Hodge 1990;Maes et al 1997b). Activation of the IRS has also been observed in the olfactory bulbectomized and the mild stress rat model of depression Sluzewska et al 1994).…”