The temporal redistribution pattern of NK cells under acute stress based on CD62L adhesion molecule expression

The Role of Norepinephrine and α-Adrenergic Receptors in Acute Stress-Induced Changes in Granulocytes and Monocytes

OBJECTIVE

Acute stress induces redistribution of circulating leucocytes in humans. Although effects on lymphocytes as adaptive immune cells are well understood, the mechanisms underlying stress effects on granulocytes and monocytes as innate immune blood cells are still elusive. We investigated whether the stress hormone norepinephrine (NE) and α-adrenergic receptors (α-ADRs) may play a mediating role.

METHODS

In a stress study, we cross-sectionally tested 44 healthy men for associations between stress-induced NE increases and simultaneous granulocyte and monocyte cell count increases, as measured immediately before and several times after the Trier Social Stress Test. In a subsequent infusion study, 21 healthy men participated in three different experimental trials with sequential infusions of 1- and 15-minute duration with varying substances (saline as placebo, the nonspecific α-ADR blocker phentolamine [2.5 mg/min], and NE [5 μg/min]): trial 1 = saline+saline, trial 2 = saline+NE, trial 3 = phentolamine+NE. Granulocyte and monocyte cell numbers were assessed before, immediately after, 10 minutes, and 30 minutes after infusion procedures.

RESULTS

In the stress study, higher NE related to higher neutrophil stress changes (β = .31, p = .045, R change = .09), but not epinephrine stress changes. In the infusion study, saline+NE induced significant increases in neutrophil (F(3/60) = 43.50, p < .001, η = .69) and monocyte (F(3/60) = 18.56, p < .001, η = .48) numbers compared with saline+saline. With phentolamine+NE, neutrophil (F(3/60) = 14.41, p < .001, η = .42) and monocyte counts (F(2.23/44.6) = 4.32, p = .016, η = .18) remained increased compared with saline+saline but were lower compared with saline+NE (neutrophils: F(3/60) = 19.55, p < .001, η = .494, monocytes: F(3/60) = 2.54, p = .065, η = .11) indicating partial mediation by α-ADRs. Trials did not differ in eosinophil and basophil count reactivity.

CONCLUSIONS

Our findings suggest that NE-induced immediate increases in neutrophil and monocyte numbers resemble psychosocial stress effects and can be reduced by blockade of α-ADRs.

A role for B cells in facilitating defense against an NK cell-sensitive lung metastatic tumor is revealed by stress

Stressors impair immune defenses and pose risks among cancer patients. Natural Killer cells are not the sole immune defense against tumor development. Utilizing an NK-sensitive tumor model, this study evaluated immune effects to stress and determined whether lung metastasis resulted from B cells' inability to augment tumorlytic function. Lung metastasis directly correlated with delayed lung B cell accumulation compared to NK, and T cells. Decreased interleukin-12 cytokine and CD80⁺ molecule expression by B cells correlated with decreased tumor lysis and increased tumor development. Thus, tumor defenses in the lung given stress exposure can depend on the B cell function.

Influence of physical activity and nutrition on obesity-related immune function

Research examining immune function during obesity suggests that excessive adiposity is linked to impaired immune responses leading to pathology. The deleterious effects of obesity on immunity have been associated with the systemic proinflammatory profile generated by the secretory molecules derived from adipose cells. These include inflammatory peptides, such as TNF- α , CRP, and IL-6. Consequently, obesity is now characterized as a state of chronic low-grade systemic inflammation, a condition considerably linked to the development of comorbidity. Given the critical role of adipose tissue in the inflammatory process, especially in obese individuals, it becomes an important clinical objective to identify lifestyle factors that may affect the obesity-immune system relationship. For instance, stress, physical activity, and nutrition have each shown to be a significant lifestyle factor influencing the inflammatory profile associated with the state of obesity. Therefore, the purpose of this review is to comprehensively evaluate the impact of lifestyle factors, in particular psychological stress, physical activity, and nutrition, on obesity-related immune function with specific focus on inflammation.

β-Adrenergic receptor mediated increases in activation and function of natural killer cells following repeated social disruption

Natural killer (NK) cells are specialized innate lymphocytes important in the early defense against tumor and virus bearing cells. Many factors influence the immune system's effectiveness against pathogens, including stress. Social disruption (SDR) "primes" macrophages/monocytes and dendritic cells thereby enhancing their anti-microbial function. What remains unclear is whether similar responses are evident in NK cells. Current studies investigated the cellular distribution and activation/inhibitory phenotypes of NK cells in the spleen, lung, and blood of C57BL/6 male mice following SDR. Furthermore, cytolytic activity and anti-viral cytokine production of splenic NK cells were determined. Lastly, β-adrenergic receptor (β-AR) signaling was investigated to determine possible mechanisms behind the SDR-induced NK cell alterations. Results indicated NK cells from SDR mice have increased expression of CD16 and CD69 and reduced NKG2a and Ly49a expression on splenic CD3-/DX5+ NK cells indicative of an activated phenotype, both immediately and 14h post-SDR. Administration of propranolol (10mg/kg; non-selective β-adrenergic receptor antagonist) was shown to block these "priming" effects at the 14h time-point. In the lung, SDR had similar effects on activation and inhibitory receptors 14h post-SDR, however no alterations were evident in the blood besides increased NK cells directly after SDR. Additionally, splenic NK cells from SDR mice had increased CD107a surface expression, cytolytic activity, and IFN-γ production was increased upon costimulation with IgG and IL-2 ex vivo. Collectively, these data suggest that social stress "primes" NK cells in the spleen and lung to be more proficient in their cytolytic and anti-viral/tumor effecter functions through β-adrenergic receptor dependent signaling.

A novel extract from bovine colostrum whey supports innate immune functions. II. Rapid changes in cellular immune function in humans

OBJECTIVE

To evaluate acute effects of bovine colostrum low-molecular weight fraction (CLMWF) on selected aspects of innate immune function in healthy human subjects.

METHODOLOGY

A placebo-controlled, double-blinded, randomized cross-over trial involving 12 healthy subjects, age 22-72, was conducted at NIS Labs during the year 2010. Placebo or 150 mg CLMWF was given orally. Blood was drawn immediately before and at 1 and 2h after consumption.

RESULTS

A single dose of CLMWF, when compared to placebo, resulted in rapid increase in phagocytic activity of monocytes at 1h (P<0.12) and polymorphonuclear cells at 1h (P<0.08) and 2h (P<0.03) after consumption. Observations included increased numbers of CD3(+) T cells (P<0.05), and a transient reduction in circulating CD3(-)CD56(+) natural killer (NK) cells at 1h (P<0.04), returning to normal levels at 2h after consumption (P<0.96). The relative increase of NK cells from 1 to 2h after consumption was not associated with an increase in CD69 or CD25 activation markers, suggesting that new NK cells were mobilized into circulation.

CONCLUSION

The increased phagocytic activity and rapid transient changes in NK cell numbers suggest that upon consumption, interaction of CLMWF with immune cells in the gut mucosa triggers immediate events with systemic consequences.

Effect of gender and menstrual cycle on immune system response to acute mental stress: apoptosis as a mediator

BACKGROUND/AIMS

We aimed to explore the immunological outcomes of short-term mental stress in apoptosis in peripheral lymphocytes and variations by gender and hormonal status of the individuals together with possible mediators of this interaction.

METHODS

Acute mental stress (computerized Stroop color-word interference and cold pressor tests) was applied to men (n = 17) and women (n = 16, in both follicular and luteal phases). Heart rate and blood pressure were monitored throughout the test and after the test until baseline values were recorded. Blood samples were drawn for measuring cortisol and nitric oxide (NO) levels and flow-cytometric cell counting before and after the test.

RESULTS

Activation of the stress system was ascertained by increased heart rate, blood pressure and serum cortisol levels after the test. Relative to baseline values, acute mental stress altered the distribution of T and natural killer cells. There was a significant decrease in T helper/T cytotoxic-suppressor cell ratio and an increase in apoptotic T helper cell percentage irrespective of gender or menstrual cycle phase. An increased number of natural killer cells was detected in women, whereas it was decreased in men. After stress induction, serum NO levels remained the same in women and increased in men. Although a correlation was not found between immune system changes and NO levels, glucocorticoids seem to have a role in the observed differences.

CONCLUSION

Acute mental stress triggers apoptotic T helper cell loss which was associated with stress system activation, and sex steroids affect the pattern of stress-related immune cell distribution.

Occupational Stress

Occupational stress can affect physiological and psychological homeostasis. In addition, the occupational challenges associated with firefighting and law enforcement have been linked to increased mortality ratios for ischemic heart disease when compared with other population cohorts. Laboratory studies have shown that the exacerbation of stress hormones (eg, catecholamines) following dual challenge (physical and psychological stress) may affect immune system responses, which may partially explain the link between cardiovascular disease and inflammation. Physical fitness has been shown to attenuate both cardiovascular and inflammatory cytokine responses following physical and/or psychological stress; however, criteria for safe and effective occupation-specific fitness levels have not been established. In addition, firefighters and police officers have high overweight and obesity rates, which also contribute significantly to the development of cardiovascular disease. Future investigation on the possible interaction (additive or synergistic) of obesity and psychological stress on the development of cardiovascular diseases in these professions is warranted, and a criterion for fitness level should be established for safe and effective participation in occupation-related activities.

Phenotypic characterization of gammadelta T cells mobilized in response to acute psychological stress

Gamma-delta (gammadelta) T lymphocytes are versatile cells that play key roles in bacterial clearance, wound repair, and delayed-type hypersensitivity reactions. Recently we showed that these cells are mobilized into the blood during acute psychological stress. gammadelta T lymphocytes are a heterogeneous population of cells, and the current study aimed to characterize the effects of stress on distinct gammadelta T cell populations. Twenty-nine healthy participants completed a 12min speech task. Blood samples were taken after a resting baseline, during the last two minutes of the task, and after a 15min recovery period. Flow cytometry was used to investigate the response of memory phenotypes (i.e. Naïve, Central memory, Effector Memory, and CD45RA(+) Effector Memory (EMRA)) within the delta1 and delta2 gammadelta T cell populations. Cells were further analysed on expression of adhesion molecules (CD11a, CD62L) and the NK-receptor CD94. Both the delta1 and delta2 subsets were mobilized during stress, and for both subsets, EMRA cells were mobilized to a much greater extent than the other memory phenotypes. Analysis of migration markers revealed that mobilized cells had a predominantly tissue migrating phenotype (CD11a(hi)CD62L(lo/neg)) and expressed high levels of the NK-receptor CD94. The current findings indicate that stress primarily mobilizes gammadelta memory cells that have high cytotoxic capability, tissue homing potential, and the capacity for rapid, innate-like target recognition. This selective mobilization possibly provides protection in contexts when tissue damage and antigen exposure are more likely to occur.

Natural killer cells in atopic and autoimmune diseases of the skin

Natural killer (NK) cells are best known for their ability to recognize and kill tumor cells and virally infected cells and for their ability to produce large amounts of some cytokines, such as IFN-gamma. Recent research has substantially expanded our view on the function of NK cells in the immune system in health and disease. In addition to the better-studied functions in cancer and autoimmunity, contributions from NK cells to allergies and various skin diseases have emerged. We briefly recount the traditional NK cell functions before focusing on their roles in atopic dermatitis, psoriasis, alopecia areata, and pemphigus vulgaris. Although this field is still developing, strong data are available that indicate NK cell involvement. In patients with allergic diseases, the production of T(H)2 cytokines by NK cells contributes to the known immune deviation. In patients with psoriasis, their pathophysiologic role seems to be especially the production of IFN-gamma. NK cell overactivation can be found in patients with alopecia areata and pemphigus vulgaris. Many details are still unclear; however, we believe that there is solid evidence that NK cells actively participate in a number of diseases that have not been traditionally linked to this type of lymphocyte.