Elsevier

Psychoneuroendocrinology

Volume 37, Issue 9, September 2012, Pages 1345-1368
Psychoneuroendocrinology

Stress-induced redistribution of immune cells—From barracks to boulevards to battlefields: A tale of three hormones – Curt Richter Award Winner

Presented at the 2011 ISPNE meeting
https://doi.org/10.1016/j.psyneuen.2012.05.008Get rights and content

Summary

Background

The surveillance and effector functions of the immune system are critically dependent on the appropriate distribution of immune cells in the body. An acute or short-term stress response induces a rapid and significant redistribution of immune cells among different body compartments. Stress-induced leukocyte redistribution may be a fundamental survival response that directs leukocyte subpopulations to specific target organs during stress, and significantly enhances the speed, efficacy and regulation of an immune response. Immune responses are generally enhanced in compartments (e.g., skin) that are enriched with leukocytes, and suppressed in compartments that are depleted of leukocytes during/following stress. The experiments described here were designed to elucidate the: (1) Time-course, trajectory, and subpopulation-specificity of stress-induced mobilization and trafficking of blood leukocytes. (2) Individual and combined actions of the principal stress hormones, norepinephrine (NE), epinephrine (EPI), and corticosterone (CORT), in mediating mobilization or trafficking of specific leukocyte subpopulations. (3) Effects of stress/stress hormones on adhesion molecule, L-selectin (CD62L), expression by each subpopulation to assess its adhesion/functional/maturation status.

Methods

Male Sprague Dawley rats were stressed (short-term restraint, 2–120 min), or adrenalectomized and injected with vehicle (VEH), NE, EPI, CORT, or their combinations, and blood was collected for measurement of hormones and flow cytometric quantification of leukocyte subpopulations.

Results

Acute stress induced an early increase/mobilization of neutrophils, lymphocytes, helper T cells (Th), cytolytic T cells (CTL), and B cells into the blood, followed by a decrease/trafficking of all cell types out of the blood, except neutrophil numbers that continued to increase. CD62L expression was increased on neutrophils, decreased on Th, CTL, and natural killer (NK) cells, and showed a biphasic decrease on monocytes & B cells, suggesting that CD62L is involved in mediating the redistribution effects of stress. Additionally, we observed significant differences in the direction, magnitude, and subpopulation specificity of the effects of each hormone: NE increased leukocyte numbers, most notably CD62L−/+ neutrophils and CD62L− B cells. EPI increased monocyte and neutrophil numbers, most notably CD62L−/+ neutrophils and CD62L− monocytes, but decreased lymphocyte numbers with CD62L−/+ CTL and CD62L+ B cells being especially sensitive. CORT decreased monocyte, lymphocyte, Th, CTL, and B cell numbers with CD62L− and CD62L+ cells being equally affected. Thus, naïve (CD62L+) vs. memory (CD62L−) T cells, classical (CD62L+) vs. non-classical (CD62L−) monocytes, and similarly distinct functional subsets of other leukocyte populations are differentially mobilized into the blood and trafficked to tissues by stress hormones.

Conclusion

Stress hormones orchestrate a large-scale redistribution of immune cells in the body. NE and EPI mobilize immune cells into the bloodstream, and EPI and CORT induce traffic out of the blood possibly to tissue surveillance pathways, lymphoid tissues, and sites of ongoing or de novo immune activation. Immune cell subpopulations appear to show differential sensitivities and redistribution responses to each hormone depending on the type of leukocyte (neutrophil, monocyte or lymphocyte) and its maturation/functional characteristics (e.g., non-classical/resident or classical/inflammatory monocyte, naïve or central/effector memory T cell). Thus, stress hormones could be administered simultaneously or sequentially to induce specific leukocyte subpopulations to be mobilized into the blood, or to traffic from blood to tissues. Stress- or stress hormone-mediated changes in immune cell distribution could be clinically harnessed to: (1) Direct leukocytes to sites of vaccination, wound healing, infection, or cancer and thereby enhance protective immunity. (2) Reduce leukocyte traffic to sites of inflammatory/autoimmune reactions. (3) Sequester immune cells in relatively protected compartments to minimize exposure to cytotoxic treatments like radiation or localized chemotherapy. (4) Measure biological resistance/sensitivity to stress hormones in vivo. In keeping with the guidelines for Richter Award manuscripts, in addition to original data we also present a model and synthesis of findings in the context of the literature on the effects of short-term stress on immune cell distribution and function.

Introduction

Regulated redistribution of immune cells among different body compartments is essential for effective immune surveillance and salubrious immune function (Butcher, 1990, Sprent and Tough, 1994). The blood is a critical compartment through which immune cells must pass in order to maintain their normal surveillance pathways and to rapidly reach sites of de novo immune activation (e.g., wounding, sterile tissue damage and inflammation, or antigen or pathogen entry) (Springer, 1994). Therefore, the numbers and proportions of leukocytes in the blood provide an important representation of the state of distribution of leukocytes in the body and of the state of activation of the immune system. Numerous studies have shown that stress can significantly affect immune cell distribution and function (for review see: Butts and Sternberg, 2008, Chrousos, 2010, Dhabhar, 2009b, Dhabhar and McEwen, 1997, Glaser and Kiecolt-Glaser, 2005). Stress has been defined as a constellation of events, consisting of a stimulus (stressor), that precipitates a reaction in the brain (stress perception), that in turn activates physiological fight-or-flight systems in the body (biological stress response) (Dhabhar and McEwen, 1997). It is important to recognize that the only mechanism through which a stressor can affect the brain or body is by inducing biological changes in the organism, which highlights the critical importance of stress hormones and physiological stress response. While stress can be harmful when it is chronic or long lasting (Chrousos and Kino, 2007, Glaser and Kiecolt-Glaser, 2005, Irwin et al., 1990, McEwen, 1998), it is often overlooked that a stress response has salubrious adaptive effects in the short run (Dhabhar and McEwen, 2007, Dhabhar and Viswanathan, 2005, Rosenberger et al., 2009). Therefore, a major distinguishing characteristic of stress is duration: Acute or short-term stress has been defined as stress that lasts for a period of minutes to hours, and chronic stress as stress that persists for several hours per day for weeks or months (Dhabhar and McEwen, 1997).

It is well known that acute or short-term stress induces a large-scale redistribution of immune cells in the body (for review see: Dhabhar, 1998, Dhabhar, 2009a, Dhabhar, 2009b). This redistribution is similar across many species, including humans, which suggests that it is evolutionarily significant and likely to confer an adaptive advantage (Dhabhar, 1998, Dhabhar, 2009a, Dhabhar, 2009b). Given the rapid time course and large magnitude of stress-induced immune cell redistribution, these effects of stress are important to take into account while measuring immune function, therapeutically administering stress hormones, and collecting, analyzing, and interpreting experimental and clinical data. Surprisingly, in spite of its importance, immune cell redistribution has been a relatively underappreciated, and clinically untapped, effect of stress.

Although the functional and clinical ramifications of stress-induced leukocyte redistribution have yet to be fully appreciated and harnessed, numerous studies have elegantly examined the effects of stress (Bosch et al., 2003, Brosschot et al., 1994, Dhabhar et al., 1995b, Mills et al., 1995, Schedlowski et al., 1993b, Stefanski and Gr¸ner, 2006), and exercise (Goebel and Mills, 2000, Hong et al., 2004, Nagatomi et al., 2000, Okutsu et al., 2008, Pedersen and Hoffman-Goetz, 2000) on selected leukocyte subpopulations. In a seeming contradiction, human studies have generally shown that acute stress increases blood immune cell numbers relative to resting state, while mouse and rat studies have shown that acute stress decreases blood immune cell numbers. However, these apparent contradictions may mainly be a matter of kinetics and arise when different studies examine different phases of the effects of acute stress on blood immune cell numbers. Therefore, the first series of results presented here comprehensively quantifies the effects of the early and late phases of stress on all major immune cell subpopulations. We test the hypothesis that the increase in blood immune cell numbers (which represents leukocyte mobilization into the blood) occurs early during short-term stress, while the decrease in blood immune cell numbers (which represents leukocyte traffic out of the blood and into tissues) occurs late during acute stress.

Numerous studies have also examined the effects of specific stress hormones on blood immune cell numbers (Benschop et al., 1996, Dale et al., 1974, Dhabhar et al., 1996, Fauci and Dale, 1974, Schedlowski et al., 1993a). Furthermore, it has been shown that adrenalectomy significantly reduces the magnitude of stress-induced decreases in blood leukocytes (Dhabhar et al., 1995b). Taken together, these studies suggest that the principal stress hormones, norepinephrine (NE), epinephrine (EPI) and corticosterone (CORT), that exert the widespread physiological effects of an acute stress response (Dhabhar and McEwen, 2001, Sapolsky et al., 2000), are also the major endocrine mediators of specific phases and redistribution profiles of psychological and physical (exercise) stressors on specific leukocyte subpopulations (Dhabhar and McEwen, 2001). EPI and NE have also been extensively studied as mediators of exercise-induced changes in immune cell distribution (Pedersen and Hoffman-Goetz, 2000). To our knowledge, however, no study has systematically and comprehensively elucidated the effects of stress hormones administered singly and in combination. Such elucidation of the combinatorial effects of stress hormones is important for understanding the differential contributions of NE, EPI, and CORT, that may come into effect as a result of different concentrations and combinations of these hormones being stimulated under different stress conditions (Kvetnansky et al., 1998, Pacak et al., 1998). Therefore, in the second series of results presented here we characterize and quantify individual and combined actions of NE, EPI and CORT, in mediating changes in all major leukocyte subpopulations. We hypothesized that specific stress hormones and their combinations would mediate distinct aspects of stress-induced leukocyte redistribution.

In both series of experiments we quantify changes in leukocyte expression of the adhesion molecule, L-selectin (CD62L) that mediates leukocyte rolling, the first step in the cascade of reactions that leads to leukocyte adhesion and transmigration, critical steps for leukocyte surveillance pathways and leukocyte response to immune activation/inflammation (Butcher and Picker, 1996, Khan et al., 2003, Wedepohl et al., 2011). Given its critical role in the adhesion cascade, we hypothesized that stress and stress hormones would change leukocyte CD62L expression. Additionally, the presence or absence of CD62L on an immune cell can be used to approximate its functional or maturation status. For example, CD62L+ Th and CTLs cells are thought to be either naïve or central memory T cells while CD62L− Th and CTLs are thought to be effector T cells (Seder and Ahmed, 2003). Similarly, CD62L+ monocytes are thought to be classical/inflammatory monocytes while CD62L− monocytes are thought to be non-classical monocytes (Gordon and Taylor, 2005, Tacke and Randolph, 2006). Therefore, we used the presence or absence of CD62L to characterize and quantify the differential effects of stress and stress hormones on specific functional/maturation phenotypes within each leukocyte subpopulation.

Studies such as these are important because they could conceivably lead to clinical applications that harness stress physiology to direct/enhance protective immune responses during vaccination, wound healing, infection, or cancer, to reduce leukocyte traffic to sites of inflammatory/autoimmune reactions, to sequester immune cells in certain compartments to minimize exposure to cytotoxic treatments like radiation or localized chemotherapy, and to monitor as a measure of stress hormone resistance/sensitivity. These studies also have important implications for experimental design and for the interpretation of experimental and clinical/diagnostic data. To our knowledge, these studies are the first to simultaneously quantify stress-induced changes in all major leukocyte subpopulations and their distinct functional subtypes, during the early (mobilization) as well as late (trafficking) phases of the leukocyte redistribution stress response. To our knowledge, these studies are also the first to quantify the combinatorial effects of simultaneously administering stress hormone combinations that mimic and elucidate the effects of NE, EPI, and CORT, which are the major mediators of the stress-induced changes in immune cell distribution. Based on data presented here as well as what is known in the literature, we propose a model explaining how stress hormones represent a “call to arms” and induce the body's “soldiers” (immune cells) to leave their “barracks” (marginated pool, spleen, bone marrow), travel through the “boulevards” (blood vessels) and take up positions at ongoing or potential “battlefields” (e.g., skin, gastro-intestinal tract, uro-genital tract) during or following stress.

Section snippets

Animals

Male Sprague Dawley rats (200–300 g) (Harlan Sprague Dawley, Indianapolis, IN) were used in all experiments. Animals were housed (3 per cage) in the accredited (American Association of Accreditation of Laboratory Animal Care) animal facilities of The Rockefeller University (New York, NY). Experiments were conducted according to protocols approved by The Rockefeller University Laboratory Animal Care and Use Committee. Animal rooms were maintained on a 12-h light-dark cycle (lights on at 7 a.m.

Acute stress-induced changes in norepinephrine (NE), epinephrine (EPI), and corticosterone (CORT)

Fig. 1 shows stress-induced changes in NE, EPI, and CORT. Acute stress increased circulating concentrations of the three principal stress hormones, NE (resting = 3881 + 550 pg/ml; stress = 5245 + 659 pg/ml, nss), EPI (resting = 7537 + 910 pg/ml; stress = 9846 + 540 pg/ml, nss), and CORT (resting = 65 + 31 ng/ml; stress = 791 + 44 ng/ml, p < 0.05). Relative to resting state baseline levels, NE and EPI reached peak concentrations at 6 min after the beginning of stress (nss), while circulating CORT showed a significant increase

Kinetics of stress-induced mobilization and trafficking of blood immune cells

It is important to recognize that a short-term increase in blood leukocytes (as seen during acute stress) reflects a mobilization of cells into the blood from certain compartments (e.g., marginated pool, spleen, bone marrow, lung, lymph nodes). In contrast, a short-term decrease in blood leukocyte numbers represents a trafficking of cells out of the blood to target organs such as the skin (Dhabhar and McEwen, 1996) and lung (Kradin et al., 2001), or sites of immune activation (Dhabhar and

Conclusion

These studies take an important step towards comprehensively elucidating the kinetics, subpopulation specificity, and hormonal mechanisms mediating stress-induced changes in blood leukocyte distribution. To our knowledge these studies are the first to characterize and quantify numbers of specific immune cell populations and functional/maturation subtypes within the major leukocyte populations, during a complete time course of early and late changes induced by an acute or short-term stress

Role of funding source

Funding sources played no role in study design or any other process related to this manuscript except for providing the greatly-appreciated financial support.

Conflict of interest

The authors declare no conflicts of interest with regards to this manuscript.

Acknowledgments

We thank Maryse Aubourg for help with some of the experiments, and Sue Moseley for conducting the catecholamine assays. These studies and the writing of this manuscript would not have been possible without support from The John D. & Catherine T. MacArthur Foundation (BSM, FSD), The DeWitt Wallace Foundation Fellowship (FSD), The Dana Foundation (FSD), NIH grants AI48995, AR46299, CA107498, and startup support from the Carl & Elizabeth Naumann Fund (FSD).

References (124)

  • J.P. Campbell et al.

    Acute exercise mobilises CD8+ T lymphocytes exhibiting an effector-memory phenotype

    Brain Behav. Immun.

    (2009)
  • J.E. Cunnick et al.

    Evidence that shock-induced immune suppression is mediated by adrenal hormones and peripheral beta-adrenergic receptors

    Pharmacol. Biochem. Behav.

    (1990)
  • E.R. De Kloet

    Steroids, stability and stress

    Front. Neuroendocrinol.

    (1995)
  • F.S. Dhabhar et al.

    Acute stress enhances while chronic stress suppresses immune function in vivo: a potential role for leukocyte trafficking

    Brain Behav. Immun.

    (1997)
  • F.S. Dhabhar et al.

    Bidirectional effects of stress on immune function: possible explanations for salubrious as well as harmful effects

  • F.S. Dhabhar et al.

    Stress response, adrenal steroid receptor levels, and corticosteroid-binding globulin levels—a comparison between Sprague Dawley, Fischer 344, and Lewis rats

    Brain Res.

    (1993)
  • F.S. Dhabhar et al.

    Differential activation of adrenal steroid receptors in neural and immune tissues of Sprague Dawley, Fischer 344, and Lewis rats

    J. Neuroimmunol.

    (1995)
  • F.S. Dhabhar et al.

    Diurnal and stress-induced changes in distribution of peripheral blood leukocyte subpopulations

    Brain Behav. Immun.

    (1994)
  • F.S. Dhabhar et al.

    Short-term stress enhances cellular immunity and increases early resistance to squamous cell carcinoma

    Brain Behav. Immun.

    (2010)
  • H. Engler et al.

    Effects of social stress on blood leukocyte distribution: the role of alpha- and beta-adrenergic mechanisms

    J. Neuroimmunol.

    (2004)
  • G.B. Glavin et al.

    Restraint stress in biomedical research: an update

    Neurosci. Biobehav. Rev.

    (1994)
  • S. Hong et al.

    Effects of regular exercise on lymphocyte subsets and CD62L after psychological vs. physical stress

    J. Psychosom. Res.

    (2004)
  • M. Irwin et al.

    Reduction of immune function in life stress and depression

    Biol. Psychiatry

    (1990)
  • A. Kavelaars

    Regulated expression of [alpha]-1 adrenergic receptors in the immune system

    Brain Behav. Immun.

    (2002)
  • A.P. Kohm et al.

    Norepinephrine: a messenger from the brain to the immune system

    Immunol. Today

    (2000)
  • R. Kradin et al.

    Epinephrine yields translocation of lymphocytes to the lung

    Exp. Mol. Pathol.

    (2001)
  • A.L. Marsland et al.

    Stress, immune reactivity, and susceptibility to infectious disease

    Physiol. Behav.

    (2002)
  • A.H. Miller

    Depression and immunity: a role for T cells?

    Brain Behav. Immun.

    (2010)
  • P.J. Mills et al.

    Lymphocyte subset redistribution in response to acute experimental stress: effects of gender, ethnicity, hypertension, and the sympathetic nervous system

    Brain Behav. Immun.

    (1995)
  • P.J. Mills et al.

    Immune cell CD62L and CD11a expression in response to a psychological stressor in human hypertension

    Brain Behav. Immun.

    (2003)
  • M. Okutsu et al.

    The effects of acute exercise-induced cortisol on CCR2 expression on human monocytes

    Brain Behav. Immun.

    (2008)
  • M. Orchinik

    Glucocorticoids, stress, and behavior: shifting the timeframe

    Horm. Behav.

    (1998)
  • P.M. Plotsky et al.

    Early, postnatal experience alters hypothalamic corticotropin-releasing factor (CRF) mRNA, median eminence CRF content, and stress-induced release in adult rats

    Brain Res. Mol. Brain Res.

    (1993)
  • T.H. Rainer et al.

    Adrenaline upregulates monocyte L-selectin in vitro

    Resuscitation

    (1999)
  • I. Rinner et al.

    Opposite effects of mild and severe stress on in vitro activation of rat peripheral blood lymphocytes

    Brain Behav. Immun.

    (1992)
  • V.M. Sanders

    Interdisciplinary research: noradrenergic regulation of adaptive immunity

    Brain Behav. Immune.

    (2006)
  • R. Ader

    Psychoneuroimmunology IV

    (2007)
  • S.F. Akana et al.

    Constant corticosterone replacement normalizes basal adrenocorticotropin (ACTH) but permits sustained ACTH hypersecretion after stress in adrenalectomized rats

    Endocrinology

    (1988)
  • C.T. Ambrose

    The requirement for hydrocortisone in antibody-forming tissue cultivated in serum-free medium

    J. Exp. Med.

    (1964)
  • S.J. Bae et al.

    Involvement of L-selectin in contact hypersensitivity responses augmented by auditory stress

    Am. J. Pathol.

    (2011)
  • A.N. Barclay

    The localization of populations of lymphocytes defined by monoclonal antibodies in rat lymphoid tissues

    Immunology

    (1981)
  • M. Baum et al.

    The role of the spleen in the leucocytosis of exercise: consequences for physiology and pathophysiology

    Int. J. Sports Med.

    (1996)
  • S.D. Bilbo et al.

    Short day lengths augment stress-induced leukocyte trafficking and stress-induced enhancement of skin immune function

    Proc. Natl. Acad. Sci. U.S.A.

    (2002)
  • R.J. Brideau et al.

    Two subsets of rat T lymphocytes defined with monoclonal antibodies

    Eur. J. Immunol.

    (1980)
  • J.F. Brosschot et al.

    Influence of life stress on immunological reactivity to mild psychological stress

    Psychosom. Med.

    (1994)
  • E.C. Butcher

    Warner-Lambert/Parke-Davis Award lecture. Cellular and molecular mechanisms that direct leukocyte traffic

    Am. J. Pathol.

    (1990)
  • E.C. Butcher et al.

    Lymphocyte homing and homeostasis

    Science

    (1996)
  • G.P. Chrousos

    Stress and sex versus immunity and inflammation

    Sci. Signal.

    (2010)
  • G.P. Chrousos et al.

    Glucocorticoid action networks and complex psychiatric and/or somatic disorders

    Stress (Amsterdam, Netherlands)

    (2007)
  • D.C. Dale et al.

    Alternate day prednisone leukocyte kinetics and susceptibility to infections

    N. Engl. J. Med.

    (1974)
  • Cited by (407)

    View all citing articles on Scopus
    View full text