Splenic norepinephrine depletion following acute stress suppresses in vivo antibody response S.L. Kennedy, M. Nickerson, J. Campisi, J.D. Johnson, T.P. Smith, C. Sharkey, M. Fleshner * Department of Integrative Physiology, University of Colorado, Campus Box 354, Boulder, Colorado 80309-0354, USA Received 11 April 2005; accepted 6 May 2005 Abstract Exposure to an intense acute stressor immediately following immunization leads to a reduction in anti-KLH IgM, IgG, and IgG2a, but not IgG1. Stress also depletes splenic norepinephrine (NE) content. Immunization during pharmacological (a-methyl-p-tyrosine) or stress- induced splenic NE depletion results in antibody suppression similar to that found in rats immunized prior to stressor exposure. Prevention of splenic NE depletion during stress by tyrosine, but not pharmacological elevation (mirtazapine) of NE, resulted in normal antibody responses. These data support the hypothesis that splenic NE depletion is necessary and sufficient for stress-induced suppression of antibody to a T-cell dependent antigen. D 2005 Elsevier B.V. All rights reserved. Keywords: Norepinephrine; Stress; Rodent; Spleen; Antibody 1. Introduction The importance of bidirectional communication between the nervous system and the immune system is becoming increasingly evident. Histological examination of the spleen demonstrates the presence of sympathetic nerve terminals in the white pulp (Felten et al., 1988), and norepinephrine (NE) produced by these sympathetic nerves may modulate cellular function by acting on beta-2 adrenergic receptors on B cells and Th1 cells (Sanders et al., 1997). Interestingly, IgM, IgG, and IgG2a, which require Th1 and B cell activation, are suppressed following exposure to acute stress, while IgG1, which requires Th2 and B cell activation, is not (Fleshner et al., 1995a, 1996; Moraska and Fleshner, 2001). Because of its role in both the stress response and immune activation, sympathetic nervous system (SNS) activity in the spleen has been implicated in mediating stress-induced immunosuppression (Wan et al., 1993). While corticosterone also plays a role in both the stress and immune responses, corticosterone injection at doses that replicate stress-induced increases do not replicate stress- induced suppression (Fleshner et al., 1996) and adrenalec- tomy prior to stress does not prevent the immunosuppres- sion (Cunnick et al., 1990). The current studies therefore focus on the role of NE in mediating the in vivo stress- induced suppression of a T-cell dependent antibody response. One key component of the acute stress response is activation of the SNS. Once activated, the SNS releases NE into immune tissues, resulting in transient increases in NE concentrations. In vitro studies have suggested that exposure of immune cells to elevated concentrations of NE can suppress immune function. For example, del Rey et al. (2003) demonstrated thymocytes incubated with NE or the non-specific beta agonist isoproteronol undergo apoptosis, 0165-5728/$ - see front matter D 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.jneuroim.2005.05.001 Abbreviations: SNS, sympathetic nervous system; NE, norepinephrine; TYR, tyrosine; AMPT, alpha-methyl-p-tyrosine; SAL, saline; KLH, key- hole limpet hemocyanin; IS, inescapable tailshock; HCC, home cage control; ELISA, enzyme-linked immunosorbant assay; HPLC, high performance liquid chromatography; PBS-T, phosphate buffered saline with Tween 20; 6-OHDA, 6-hydroxydopamine; HPA, hypothalamic- pituitary-adrenal. * Corresponding author. Tel.: +1 303 492 1483; fax: +1 303 492 6778. E-mail address: fleshner@spot.colorado.edu (M. Fleshner). Journal of Neuroimmunology 165 (2005) 150 – 160 www.elsevier.com/locate/jneuroim