Tracking Self-reported Symptoms and Medical Conditions on Social Media During the COVID-19 Pandemic: Infodemiological Study.

BACKGROUND: Harnessing health-related data posted on social media in real time can offer insights into how the pandemic impacts the mental health and general well-being of individuals and populations over time. OBJECTIVE: This study aimed to obtain information on symptoms and medical conditions self-reported by non-Twitter social media users during the COVID-19 pandemic, to determine how discussion of these symptoms and medical conditions changed over time, and to identify correlations between frequency of the top 5 commonly mentioned symptoms post and daily COVID-19 statistics (new cases, new deaths, new active cases, and new recovered cases) in the United States. METHODS: We used natural language processing (NLP) algorithms to identify symptom- and medical condition-related topics being discussed on social media between June 14 and December 13, 2020. The sample posts were geotagged by NetBase, a third-party data provider. We calculated the positive predictive value and sensitivity to validate the classification of posts. We also assessed the frequency of health-related discussions on social media over time during the study period, and used Pearson correlation coefficients to identify statistically significant correlations between the frequency of the 5 most commonly mentioned symptoms and fluctuation of daily US COVID-19 statistics. RESULTS: Within a total of 9,807,813 posts (nearly 70% were sourced from the United States), we identified a discussion of 120 symptom-related topics and 1542 medical condition-related topics. Our classification of the health-related posts had a positive predictive value of over 80% and an average classification rate of 92% sensitivity. The 5 most commonly mentioned symptoms on social media during the study period were anxiety (in 201,303 posts or 12.2% of the total posts mentioning symptoms), generalized pain (189,673, 11.5%), weight loss (95,793, 5.8%), fatigue (91,252, 5.5%), and coughing (86,235, 5.2%). The 5 most discussed medical conditions were COVID-19 (in 5,420,276 posts or 66.4% of the total posts mentioning medical conditions), unspecified infectious disease (469,356, 5.8%), influenza (270,166, 3.3%), unspecified disorders of the central nervous system (253,407, 3.1%), and depression (151,752, 1.9%). Changes in posts in the frequency of anxiety, generalized pain, and weight loss were significant but negatively correlated with daily new COVID-19 cases in the United States (r=-0.49, r=-0.46, and r=-0.39, respectively; P<.05). Posts on the frequency of anxiety, generalized pain, weight loss, fatigue, and the changes in fatigue positively and significantly correlated with daily changes in both new deaths and new active cases in the United States (r ranged=0.39-0.48; P<.05). CONCLUSIONS: COVID-19 and symptoms of anxiety were the 2 most commonly discussed health-related topics on social media from June 14 to December 13, 2020. Real-time monitoring of social media posts on symptoms and medical conditions may help assess the population's mental health status and enhance public health surveillance for infectious disease.

Engagement With COVID-19 Public Health Measures in the United States: A Cross-sectional Social Media Analysis from June to November 2020.

BACKGROUND: COVID-19 has continued to spread in the United States and globally. Closely monitoring public engagement and perceptions of COVID-19 and preventive measures using social media data could provide important information for understanding the progress of current interventions and planning future programs. OBJECTIVE: The aim of this study is to measure the public's behaviors and perceptions regarding COVID-19 and its effects on daily life during 5 months of the pandemic. METHODS: Natural language processing (NLP) algorithms were used to identify COVID-19-related and unrelated topics in over 300 million online data sources from June 15 to November 15, 2020. Posts in the sample were geotagged by NetBase, a third-party data provider, and sensitivity and positive predictive value were both calculated to validate the classification of posts. Each post may have included discussion of multiple topics. The prevalence of discussion regarding these topics was measured over this time period and compared to daily case rates in the United States. RESULTS: The final sample size included 9,065,733 posts, 70% of which were sourced from the United States. In October and November, discussion including mentions of COVID-19 and related health behaviors did not increase as it had from June to September, despite an increase in COVID-19 daily cases in the United States beginning in October. Additionally, discussion was more focused on daily life topics (n=6,210,255, 69%), compared with COVID-19 in general (n=3,390,139, 37%) and COVID-19 public health measures (n=1,836,200, 20%). CONCLUSIONS: There was a decline in COVID-19-related social media discussion sourced mainly from the United States, even as COVID-19 cases in the United States increased to the highest rate since the beginning of the pandemic. Targeted public health messaging may be needed to ensure engagement in public health prevention measures as global vaccination efforts continue.

Prevention of liver metastases through perioperative acute CpG-C immune stimulation.

Following excision of colorectal tumors, metastatic disease is prevalent, primarily occurs in the liver, and is highly predictive of poor prognosis. The perioperative period is now recognized as critical in determining the incidence of postoperative metastases and long-term cancer outcomes. Thus, various perioperative prophylactic interventions are currently studied during this time frame. However, immune stimulation during the perioperative period has rarely been attempted due to specific contraindications to surgery and various adverse effects. Here, to prevent liver metastases, we perioperatively employed a TLR-9 agonist, CpG-C, which exhibits minimal pyrogenic and other adverse effects in patients. We found that marginating-hepatic (MH) cells in BALB/c mice contained high percentage of NK cells, but exhibited negligible NK cytotoxicity, as previously reported in humans. However, a single CpG-C administration (25-100 µg/mouse) doubled MH-NK cell numbers, increased NK cell activation and maturation markers (NKp46, CD11b), decreased the inhibitory NKG2A ligand, and dramatically increased MH-NK-cell cytotoxicity against the syngeneic CT26 colon cancer line. Moreover, in operated mice, this innocuous intervention also markedly improved resistance to CT26 and MC38 hepatic metastases in BALB/c and C57BL/6 mice, respectively. Beneficial effects of CpG-C were mediated through activation of MH-NK cells, as indicated by an in vivo NK depletion study. Last, CpG-C protected against surgery-induced suppression of MH-NK cytotoxicity and improved their activation indices. Thus, we suggest that systemic perioperative CpG-C treatment should be considered and studied as a novel therapeutic approach to improve long-term cancer outcomes in colorectal cancer patients.

Harnessing cancer immunotherapy during the unexploited immediate perioperative period.

The immediate perioperative period (days before and after surgery) is hypothesized to be crucial in determining long-term cancer outcomes: during this short period, numerous factors, including excess stress and inflammatory responses, tumour-cell shedding and pro-angiogenic and/or growth factors, might facilitate the progression of pre-existing micrometastases and the initiation of new metastases, while simultaneously jeopardizing immune control over residual malignant cells. Thus, application of anticancer immunotherapy during this critical time frame could potentially improve patient outcomes. Nevertheless, this strategy has rarely been implemented to date. In this Perspective, we discuss apparent contraindications for the perioperative use of cancer immunotherapy, suggest safe immunotherapeutic and other anti-metastatic approaches during this important time frame and specify desired characteristics of such interventions. These characteristics include a rapid onset of immune activation, avoidance of tumour-promoting effects, no or minimal increase in surgical risk, resilience to stress-related factors and minimal induction of stress responses. Pharmacological control of excess perioperative stress-inflammatory responses has been shown to be clinically feasible and could potentially be combined with immune stimulation to overcome the direct pro-metastatic effects of surgery, prevent immune suppression and enhance immunostimulatory responses. Accordingly, we believe that certain types of immunotherapy, together with interventions to abrogate stress-inflammatory responses, should be evaluated in conjunction with surgery and, for maximal effectiveness, could be initiated before administration of adjuvant therapies. Such strategies might improve the overall success of cancer treatment.

Deleterious synergistic effects of distress and surgery on cancer metastasis: Abolishment through an integrated perioperative immune-stimulating stress-inflammatory-reducing intervention.

The perioperative period holds disproportionate impact on long-term cancer outcomes. Nevertheless, perioperative interventions to improve long-term cancer outcomes are not clinical routines, including perioperative stress-reducing or immune-stimulating approaches. Here, mimicking the clinical setting of pre-operative distress, followed by surgery, we examined the separate and combined effects of these events on the efficacy of pre-operative immune stimulation in rats and mice, and on post-operative resistance to tumor metastasis of the syngeneic mammary adenocarcinoma MADB106 in F344 rats and the CT26 colon carcinoma in Balb/C mice. The novel immune stimulating agents, GLA-SE or CpG-C (TLR-4 and TLR-9 agonists, respectively), were employed pre-operatively. Sixteen hours of pre-operative behavioral stressors (i) lowered CpG-C induced plasma IL-12 levels, and reduced resistance to MADB106 and CT-26 experimental metastases, and (ii) worsened the deleterious effects of laparotomy on metastasis in both tumor models. In rats, these effects of pre-operative stress were further studied and successfully abolished by the glucocorticoid receptor antagonist RU-486. Additionally, in vitro studies indicated the dampening effect of corticosterone on immune stimulation. Last, we tested a perioperative integrated intervention in the context of pre-operative stress and laparotomy, based on (i) antagonizing the impact of glucocorticoids before surgery, (ii) activating anti-metastatic immunity perioperatively, and (iii) blocking excessive operative and post-operative adrenergic and prostanoid responses. This integrated intervention successfully and completely abolished the deleterious effects of stress and of surgery on post-operative resistance to experimental metastasis. Such and similar integrated approaches can be studied clinically in cancer patients.

Regeneration of Functional Adrenal Tissue Following Bilateral Adrenalectomy.

It is assumed that after complete bilateral adrenalectomy (ADX), no adrenal tissue will redevelop and adrenal hormone levels will remain low and unaffected by stress. However, anecdotal observations in animals and in patients suggest that under some unknown circumstances the opposite can occur. Herein, we studied whether adrenalectomized rats can develop an alternative source of systemic corticosterone after complete bilateral ADX with minimal replacement therapy. Male and female rats underwent either a standard ADX, in which the glands were removed with minimal surrounding adipose tissue, or an extensive ADX, in which glands were removed with most surrounding adipose tissue. Excised glands were histologically tested for completeness, and corticosterone replacement was nullified within 1 to 3 weeks postoperatively. In four experiments and in both excision approaches, some rats gradually reestablished baseline corticosterone levels and stress response in a time-dependent manner, but differences were observed in the reestablishing rates: 80% in standard ADX vs 20% in extensive ADX. Upon searching for the source of corticosterone secretion, we were surprised to find functional macroscopic foci of adrenocortical tissue without medullary tissue, mostly proximal to the original location. Chronic stress accelerated corticosterone level reestablishment. We hypothesized that underlying this phenomenon were preexisting ectopic microscopic foci of adrenocortical-like tissue or a few adrenal cells that were pre-embedded in surrounding tissue or detached from the excised gland upon removal. We concluded that adrenalectomized animals may develop compensatory mechanisms and suggest that studies employing ADX consider additional corticosterone supplementation, minimize stress, and verify the absence of circulating corticosterone.

Perioperative COX-2 and ß-Adrenergic Blockade Improves Metastatic Biomarkers in Breast Cancer Patients in a Phase-II Randomized Trial.

Purpose: Translational studies suggest that excess perioperative release of catecholamines and prostaglandins may facilitate metastasis and reduce disease-free survival. This trial tested the combined perioperative blockade of these pathways in breast cancer patients.Experimental Design: In a randomized placebo-controlled biomarker trial, 38 early-stage breast cancer patients received 11 days of perioperative treatment with a ß-adrenergic antagonist (propranolol) and a COX-2 inhibitor (etodolac), beginning 5 days before surgery. Excised tumors and sequential blood samples were assessed for prometastatic biomarkers.Results: Drugs were well tolerated with adverse event rates comparable with placebo. Transcriptome profiling of the primary tumor tested a priori hypotheses and indicated that drug treatment significantly (i) decreased epithelial-to-mesenchymal transition, (ii) reduced activity of prometastatic/proinflammatory transcription factors (GATA-1, GATA-2, early-growth-response-3/EGR3, signal transducer and activator of transcription-3/STAT-3), and (iii) decreased tumor-infiltrating monocytes while increasing tumor-infiltrating B cells. Drug treatment also significantly abrogated presurgical increases in serum IL6 and C-reactive protein levels, abrogated perioperative declines in stimulated IL12 and IFNγ production, abrogated postoperative mobilization of CD16- "classical" monocytes, and enhanced expression of CD11a on circulating natural killer cells.Conclusions: Perioperative inhibition of COX-2 and ß-adrenergic signaling provides a safe and effective strategy for inhibiting multiple cellular and molecular pathways related to metastasis and disease recurrence in early-stage breast cancer. Clin Cancer Res; 23(16); 4651-61. ©2017 AACR.

Selective Harvesting of Marginating-hepatic Leukocytes.

Marginating-hepatic (MH) leukocytes (leukocytes adhering to the sinusoids of the liver), were shown to exhibit unique composition and characteristics compared to leukocytes of other immune compartments. Specifically, evidence suggests a distinct pro- and anti-inflammatory profile of the MH-leukocyte population and higher cytotoxicity of liver-specific NK cells (namely, pit cells) compared to circulating or splenic immunocytes in both mice and rats. The method presented herein enables selective harvesting of MH leukocytes by forced perfusion of the liver in mice and rats. In contrast to other methods used to extract liver-leukocytes, including tissue grinding and biological degradation, this method exclusively yields leukocytes from the liver sinusoids, uncontaminated by cells from other liver compartments. In addition, the perfusion technique better preserves the integrity and the physiological milieu of MH leukocytes, sparing known physiological responses to tissue processing. As many circulating malignant cells and infected cells are detained while passing through the liver sinusoids, physically interacting with endothelial cells and resident leukocytes, the unique MH leukocyte population is strategically located to interact, identify, and react towards aberrant circulating cells. Thus, selective harvesting of MH-leukocytes and their study under various conditions may advance our understanding of the biological and clinical significance of MH leukocytes, specifically with respect to circulating aberrant cells and liver-related diseases and cancer metastases.

Reducing liver metastases of colon cancer in the context of extensive and minor surgeries through ß-adrenoceptors blockade and COX2 inhibition.

Liver metastases are a major cause of colorectal cancer death, and the perioperative period is believed to critically affect the metastatic process. Here we tested whether blocking excess release of catecholamines and prostaglandins during surgical procedures of different extent can reduce experimental liver metastasis of the syngeneic CT26 colon cancer in female and male BALB/c mice. Animals were either treated with the beta-blocker, propranolol, the COX-2 inhibitor, etodolac, both drugs, or vehicle. The role of NK cells in controlling CT26 hepatic metastasis and in mediating the effect of the drugs was assessed by in vivo depletion or stimulation of NK cells, using anti-asialo GM1 or CpG-C, respectively. Surgical extent was manipulated by adding laparotomy to small incision, extending surgical duration, and enabling hypothermia. The results indicated that combined administration of propranolol and etodolac, but neither drug alone, significantly improved host resistance to metastasis. These beneficial effects occurred in both minor and extensive surgeries, in both sexes, and in two tumor inoculation approaches. NK cell-mediated anti-CT26 activity is involved in mediating the beneficial effects of the drugs. Specifically, CpG-C treatment, known to profoundly activate mice marginating-hepatic NK cytotoxicity, reduced CT26 hepatic metastases; and NK-depletion increased metastases and prevented the beneficial effects of the drugs. Overall, given prevalent perioperative psychological and physiological stress responses in patients, and ample prostaglandin release by colorectal tumors and injured tissue, propranolol and etodolac could be tested clinically in laparoscopic and open colorectal surgeries, attempting to reduce patients' metastatic disease.

Perioperative treatment with the new synthetic TLR-4 agonist GLA-SE reduces cancer metastasis without adverse effects.

The use of TLR agonists as an anti-cancer treatment is gaining momentum given their capacity to activate various host cellular responses through the secretion of inflammatory cytokines and type-I interferons. It is now also recognized that the perioperative period is a window of opportunity for various interventions aiming at reducing the risk of cancer metastases-the major cause of cancer related death. However, immune-stimulatory approach has not been used perioperatively given several contraindications to surgery. To overcome these obstacles, in this study, we used the newly introduced, fully synthetic TLR-4 agonist, Glucopyranosyl Lipid-A (GLA-SE), in various models of cancer metastases, and in the context of acute stress or surgery. Without exerting evident adverse effects, a single systemic administration of GLA-SE rapidly and dose dependently elevated both innate and adaptive immunity in the circulation, lungs and the lymphatic system. Importantly, GLA-SE treatment led to reduced metastatic development of a mammary adenocarcinoma and a colon carcinoma by approximately 40-75% in F344 rats and BALB/c mice, respectively, at least partly through elevating marginating-pulmonary NK cell cytotoxicity. GLA-SE is safe and well tolerated in humans, and currently is used as an adjuvant in phase-II clinical trials. Given that the TLR-4 receptor and its signaling cascade is highly conserved throughout evolution, our current results suggest that GLA-SE may be a promising immune stimulatory agent in the context of oncological surgeries, aiming to reduce long-term cancer recurrence.

The misleading nature of in vitro and ex vivo findings in studying the impact of stress hormones on NK cell cytotoxicity.

In vitro and ex vivo studies assessing the impact of stress hormones on immune competence commonly replace the natural milieu of leukocytes with an artificial medium, excluding plasma factors, hormones, and cytokines. Given prevalent inconsistencies between in vitro, ex vivo, and in vivo findings, we studied whether such procedures could yield misleading outcomes regarding the impact of stress hormones on NK cell cytotoxicity (NKCC), using fresh human whole blood samples. We found that in the presence of plasma 10-30-fold higher concentrations of cortisol, epinephrine, and prostaglandin-E2 (PGE2) were required to reach suppression levels evident in the context of artificial medium. Importantly, whereas the NK suppressive effects of PGE2 occurred immediately and remained stable upon prolonged exposure, the suppressive effects of cortisol slowly increased over time. Last, to simulate the exclusion of stress factors in the ex vivo approach, we subjected whole blood to stress hormones (as occurs in vivo), and abruptly removed them. We found that the effects of epinephrine and PGE2 quickly disappeared, while the effects of cortisol persisted. Overall, these findings demonstrate the potential misleading nature of in vitro and ex vivo procedures, and specifically suggest that (i) the common in vitro findings of profound suppression of NKCC by stress hormones are overestimation of their direct effects expected in vivo; and (ii) the common ex vivo approach cannot reflect the direct in vivo suppressive effects of epinephrine and PGE2 on NKCC, while inflating the effects of glucocorticoids. Some of these fallacies may be circumvented by using non-delayed whole blood NKCC assays in humans.

Plasma IL-12 levels are suppressed in vivo by stress and surgery through endogenous release of glucocorticoids and prostaglandins but not catecholamines or opioids.

IL-12 is a prominent Th1 differentiator and leukocyte activator. Ample studies showed suppression of IL-12 production by numerous stress factors, including prostaglandins, catecholamines, glucocorticoids, and opioids, but did so in vitro and in the context of artificial leukocyte activation, not simulating the in vivo setting. In a recent study we reported in vivo suppression of plasma IL-12 levels by behavioral stress and surgery. The current study aims to elucidate neuroendocrine mechanisms underlying this phenomenon in naïve F344 rats. To this end, both adrenalectomy and administration of specific antagonists were used, targeting the aforementioned stress factors. The results indicated that corticosterone and prostaglandins are prominent mediators of the IL-12-suppressing effects of stress and surgery, apparently through directly suppressing leukocyte IL-12 production. Following surgery, endogenous prostaglandins exerted their effects mainly through elevating corticosterone levels. Importantly, stress-induced release of epinephrine or opioids had no impact on plasma IL-12 levels, while pharmacological administration of epinephrine reduced plasma IL-12 levels by elevating corticosterone levels. Last, a whole blood in vitro study indicated that prostaglandins and corticosterone, but not epinephrine, suppressed IL-12 production in non-stimulated leukocytes, and only corticosterone did so in the context of CpG-C-induced IL-12 production. Overall, the findings reiterate the notion that results from in vitro or pharmacological in vivo studies cannot indicate the effects of endogenously released stress hormones under stress/surgery conditions. Herein, corticosterone and prostaglandins, but not catecholamines or opioids, were key mediators of the suppressive effect of stress and surgery on in vivo plasma IL-12 levels in otherwise naïve animals.

In vivo suppression of NK cell cytotoxicity by stress and surgery: glucocorticoids have a minor role compared to catecholamines and prostaglandins.

Most in vitro and ex-vivo studies indicate a profound suppression of NK cell cytotoxicity (NKCC) by glucocorticoids; while catecholamines and prostaglandins were reported both to suppress and to enhance NKCC. However, methodological considerations hinder our ability to deduce from these findings to the impact of endogenous release of these factors on in vivo levels of NKCC and their implications to NK-dependent resistance to pathologies in living humans or animals. Here we used an in vivo approach that sensitively and specifically reflects NKCC in living F344 rats, based on lung clearance of NK-sensitive tumor cells (MADB106), and based on comparing effects between NK-intact and NK-depleted rats. To study the role of corticosterone, epinephrine, and prostaglandins, we administered these factors to rats, or antagonized their endogenous release following different stress paradigms or surgery. The results indicated that endogenous or exogenous elevated corticosterone levels can suppress in vivo NKCC levels, but only under some conditions, and mostly secondarily to the NK-suppressing impact of epinephrine. Specifically, corticosterone-induced NKCC suppression occurred (i) only under prolonged, but not short exposure to stress, and mainly in males; (ii) was smaller than the prominent impact of epinephrine; (iii) was mostly ascribed to corticosterone-induced potentiation of the effects of epinephrine or/and prostaglandins; and (iv) was completely abolished through antagonizing epinephrine or/and prostaglandins. Overall, these findings markedly limit the significance of stress/surgery-induced corticosterone release in the in vivo suppression of NKCC, and highlight the blockade of epinephrine or/and prostaglandins as effective and clinically feasible approaches to overcome such immuno-suppressive effects.

The marginating-pulmonary immune compartment in mice exhibits increased NK cytotoxicity and unique cellular characteristics.

To test whether marginating-pulmonary (MP) leukocytes in mice have a unique potential to identify and destroy aberrant circulating cells, we compared MP to circulating leukocytes with respect to natural killer (NK) cytotoxicity, proinflammatory characteristics, molecular determinants of activation, and response to IL-12 immunostimulation. Cytotoxicity was assessed employing the YAC-1, B16F10, and 3LL target lines. C57BL/6 mice were injected with either saline or murine IL-12 (0.1 or 0.5 µg/mouse), either once or three times 48-h apart. Twenty-four hours after last injection, cardiac blood was withdrawn and MP leukocytes were collected by forced lung perfusion. NK cytotoxicity, cellular composition, and surface molecular markers were studied. MP leukocytes exhibited greater NK cytotoxicity than circulating leukocytes against the syngeneic B16F10 and 3LL tumor lines, but not against the allogeneic YAC-1 line. NKG2D and IL-12 receptor expression predicted NK cytotoxicity in circulating leukocytes, but not in MP leukocytes. IFNγ-receptor, IL-12-receptor, CD69, CD11a, and CD11b showed different patterns of expression in the two leukocyte populations, suggesting pro-inflammatory characteristics of the MP compartment. IL-12 stimulation caused differential effects on these markers and also elevated cytotoxicity in both compartments, but in different effector: target ratio-dependent patterns. MP leukocytes may play a critical role in eliminating aberrant circulating cells due to their enhanced NK cytotoxicity and given their strategic location in the lungs vasculature, which forces physical interactions with all circulating aberrant cells. MP-NK cells are unique in their cytotoxic mechanisms against syngeneic targets and in their activation profile and response to immunostimulatory agents.

Impact of surgical extent and sex on the hepatic metastasis of colon cancer.

PURPOSE: Extensive oncological surgeries were previously suggested to increase cancer recurrence rates. We herein studied the impact of different surgical procedures and sex on colorectal cancer liver metastasis, employing several tumor inoculation approaches in BALB/c mice. METHODS: Experimental hepatic metastases of the syngeneic CT26 colorectal cancer line were induced either by intra-portal inoculation or intra-splenic inoculation, employing different tumor loads. Following intra-splenic inoculation, the entire spleen or an injected hemi-spleen was removed. Additionally, the magnitude of the surgical trauma accompanying the injection procedure was manipulated. RESULTS: Increasing the surgical trauma by adding laparotomy or extending the length of the surgery and hypothermia did not significantly affect the number of liver metastases or liver weight for any of the injection methods and tumor loads. The development of metastasis was significantly greater in males than in females under all conditions studied--a difference not explained by the direct effects of sex hormones on in vitro CT26 proliferation or vitality. CONCLUSION: Concurring with less controlled clinical observations, the surgical extensiveness did not significantly affect CT26 hepatic metastasis, potentially due to a ceiling effect of the surgical trauma on the metastatic process. The sexual dimorphism observed for the CT26 metastasis should be investigated in the context of surgical stress and considering anti-CT26 immunoreactivity.

Resilience of the immune system in healthy young students to 30-hour sleep deprivation with psychological stress.

OBJECTIVE: Young adults often encounter sleep deprivation and stressful events. Both have been separately reported to modulate immunity, and occasionally they occur simultaneously. We assessed the combined effects of these conditions on immune competence in healthy students. METHODS: Twenty-three participants (mean age 24 years; SD 1.86; 14 females) were exposed to 30 h of sleep deprivation during which they conducted physiological, social and cognitive tasks. The control group consisted of 18 participants (mean age 23.67 years; SD 1.46; 11 females). All participants underwent cognitive and psychological evaluations at 10:00 AM, followed by blood and saliva collection, 3 days before sleep deprivation induction and on the morning following it. Immune/endocrine measures included blood counts of lymphocytes, granulocytes, monocytes and natural killer (NK) cells; levels of several cell surface markers; NK cytotoxicity; plasma levels of interleukin (IL)-6, IL-10, dehydroepiandrosterone and neuropeptide Y, and plasma and salivary cortisol levels. RESULTS: Although the experimental protocol significantly elevated state anxiety and psychological dissociation levels, no effects were evident in any of the immunological/endocrine indices. In contrast, expected sex differences in immune measures were found, including significantly higher NK cytotoxicity and monocyte counts in males, validating the integrity of the measurements. CONCLUSIONS: The findings suggest resilience of the immune system to a combined sleep deprivation and stressful exposure in young adults, while previous studies reported immune perturbations following either of these conditions separately. These apparent contradictions might reflect differences in the study design or in the methodology used for immunological assessments, including the time of sample collection, the combination of sleep deprivation with stress and our in vivo assessment of cytokine levels.