Impaired lymphocyte function in depressive illness

Immune correlates of depression

The relation of depression to immunological assays is complex and variable. However, meta-analyses have demonstrated that depressed subjects are likely to show changes in several immune assays. Depressed subjects are likely to have changes in major immune cell classes with an increase in total white blood cell counts and a relative increase in numbers of neutrophils. However, the relative number of lymphocytes is likely to be reduced in depressed subjects. Depression also appears to be associated with increases in at least one measure of immune activation, although further investigations are clearly needed to replicate these interesting observations. Finally, depression is reliably associated with a suppression of mitogen-induced lymphocyte proliferation and with a reduction of NK activity. Despite the heterogeneity of findings, the effect sizes in the relationship between depression and lymphocyte proliferation and NK activity are large as compared to those observed in other areas of psychological and medical research. Several moderating factors may explain and account for the heterogeneity that has been found in the depression-immune results. Future immunologic studies in depressed subjects are needed to clarify the effects of gender and reproductive hormones on the relation between depression and immunity. Severity of melancholic symptoms and sleep disturbance appear to moderate the immune changes in depression but the biological mechanisms that account for the link between these neurovegetative symptoms and depression are not yet known. Finally, assessment of co-morbidity in depressed subjects deserves an increased focus. Data generated from our laboratory clearly show that assessment of alcohol- and tobacco dependence is critical in the interpretation of immune changes in depressed subjects. The clinical significance of changes in immune responses in depressed subjects remains an unanswered question. Studies that use immune measures with disease specific endpoints, as has been recently conducted in the study of VZV immune responses, would help identify the possible link between depression, immune system alterations, and health outcomes.

Religiosity is associated with affective and immune status in symptomatic HIV-infected gay men

This study examines the relationship between religiosity and the affective and immune status of 106 HIV-seropositive mildly symptomatic gay men (CDC stage B). All men completed an intake interview, a set of psychosocial questionnaires, and provided a venous blood sample. Factor analysis of 12 religiously oriented response items revealed two distinct aspects to religiosity: religious coping and religious behavior. Religious coping (e.g., placing trust in God, seeking comfort in religion) was significantly associated with lower scores on the Beck Depression Inventory, but not with specific immune markers. On the other hand, religious behavior (e.g., service attendance, prayer, spiritual discussion, reading religious literature) was significantly associated with higher T-helper-inducer cell (CD4+) counts and higher CD4+ percentages, but not with depression. Regression analyses indicated that religiosity's associations with affective and immune status was not mediated by the subjects' sense of self-efficacy or ability to actively cope with their health situation. The associations between religiosity and affective and immune status also appear to be independent of symptom status. Self-efficacy, however, did appear to contribute uniquely and significantly to lower depression scores. Our results show that an examination considering both subject religiosity as well as sense of self-efficacy may predict depressive symptoms in HIV-infected gay men better than an examination that considers either variable in isolation.

Effect of mild chronic stress, as a model of depression, on the immunoreactivity of C57BL/6 mice

Numerous studies correlate the state of depression with some abnormalities in the immune response, such as increased numbers of white blood-cells, alterations in sub-populations of leucocytes, suppression of cytotoxic activity of natural-killer cells, increased levels of some autoantibodies and acute-phase proteins. Some of these changes have been attributed to autoimmunological reactions. While the possibilities to evaluate some reactions in depressed patients are limited, an animal model of depression could well simulate this clinical situation, and the chronic mild state of stress is a well accepted one. After undergoing stress for three-weeks, C57BL/6 mice demonstrate in the present study a decrease in thymus weight, as well as increased interleukin-1 and decreased interleukin-2 production. Splenocytes of the depressed mice exert a decrease in natural-killer-cell activity, in the proliferative response to Concanavalin-A, interleukin-1 and anti-CD3 monoclonal antibodies and an increase in the proliferative response to lipopolysaccharides and pokeweed mitogens. Our results also suggest that chronic stress-induced activation of suppressor cells in the spleen, due to elimination of CD8+ cells, increase the proliferation of splenocytes in response to mitogens of T cells.

Emotion and immunity

Earlier studies have suggested that depression is associated with decreased immune function, but a recent literature review has revealed that a majority of studies reached inconsistent or conflicting conclusions. On the other hand, studies on immune function in anxiety disorders are sparse, and their findings are also inconsistent. Despite a few contradictory results, a clinical level of anxiety seems to reduce immune function, whereas a subclinical level of anxiety seems to enhance immunity. The latter may be a transient phenomenon occurring prior to the downregulation of immune function, reflecting the body's defense to a stressor. Thus, research needs to be conducted to elucidate the relationship between those hormones related to hypothalamic-pituitary-adrenal axis and a variety of immune measures at the subclinical level of anxiety. In addition, to confirm the interaction between emotion and immune function, the effectiveness of treatment with medication and psychotherapy on immunity should be investigated.

Reduced lymphocyte proliferation and interleukin-2 production in anxiety disorders

OBJECTIVE

The purpose of this study was to examine the effect of anxiety on cell-mediated immunity.

METHOD

The subjects consisted of 31 patients with anxiety disorders and 31 normal controls, who were gender-matched. Cell-mediated immune function was measured by the lymphocyte proliferative response to phytohemagglutinin (PHA), Interleukin-2 (IL-2) production, and natural killer cell activity (NKA). The extent of anxiety was assessed by the Hamilton rating scale for anxiety and the anxiety subscale of symptom checklist-90 revised (SCL-90-R).

RESULTS

The patients with anxiety disorders were significantly lower than the normal controls in lymphocyte proliferative response to PHA and IL-2 production. However, there was no significant difference in NKA between the two groups. Also, no significant correlation was found between the duration of illness or the degree of anxiety and each immune measure in patients with anxiety disorders.

CONCLUSIONS

The results suggest a reduced cell-mediated immune function in patients with anxiety disorders, compared with normal controls. These findings also imply that a variety of immune measures should be assessed at the same time in this kind of psychoneuroimmunology research. This would help elucidate the relationship between anxiety and immune function, which has been unclear in most previous research using a single immune measure.

Neuroendocrine and immune system interactions in stress and depression

Based on the extensive characterization of communication pathways between the nervous system and the immune system, there has been increasing interest in the impact of the nervous system on the development and expression of disorders involving the immune system and the contribution of the immune system to psychiatric disease. A vast literature has documented the impact of various stressors on a wide array of immune partners, and the specific neuroendocrine pathways involved have been elucidated. The impact of cytokines on neuroendocrine function and behavior has also been determined, and the relevance of cytokines to the pathophysiology of depression has become an exciting new research frontier. This article provides a foundation for integrating neuroendocrine-immune interactions into the formulation of neuropsychiatric and immunologic disease.

A study of the immunology of the chronic fatigue syndrome: correlation of immunologic parameters to health dysfunction

Surface and intracellular immunologic and apoptotic markers and functional lymphocyte assays after stimulation with anti-CD3/anti-CD28 antibodies or phytohemagglutinin (PHA) were studied in 44 patients fulfilling the Oxford criteria for chronic fatigue syndrome (CFS). Results were then correlated to scores for the Short Form-36 health questionnaire (SF-36), which assesses eight aspects of patient's well-being, and for the general health questionnaire (GHQ), which detects current psychiatric disorder. Patients had significantly increased mean fluorescence intensity readings of HLA-DR in CD4 and CD8 cells (P < 0.05). Expression of the costimulatory receptor CD28 in CD8 cells was significantly reduced, and the apoptosis repressor ratio of bcl-2/bax in both CD4 and CD8 was increased in patients (P < 0.05). Patients with increased HLA-DR expression had significantly lower SF-36 total scores, worse body pains, and poorer general health perception and physical functioning scores. Increased spontaneous lymphocyte proliferation was associated with poor general health perception. PHA proliferative responses were lower in patients with poor emotional and mental health scores, and the anti-CD3/anti-CD28 response was low in those with low general health perception scores. Higher spontaneous proliferation and reduced PHA responses correlated with higher GHQ scores. Similarly, GHQ scores were significantly higher, indicating worse mental health, in those with lower total SF-36 scores and worse general and mental health scores in the SF-36 questionnaire. Finally, higher expression of the costimulatory molecule CD28 correlated with higher total SF-36 scores, general health perception and social functioning scores, and with lower role limitation due to physical health. The increased expression of class II antigens and the reduced expression of the costimulatory receptor CD28, which is a marker of terminally differentiated cells, lend further support to the concept of immunoactivation of T-lymphocytes in CFS and may be consistent with the notion of a viral etiopathogenesis in the illness. We report, for the first time, increased expression of the apoptosis repressor protein bcl-2, which may contribute to enhanced survival of activated lymphocytes. Using the SF-36 health assessment questionnaire and the GHQ, we demonstrated changes in different immunological parameters, each of which correlated with particular aspects of disease symptomatology.

Acute phase proteins in major depression

Extensive evidence exists associating depression with changes in the immune system. The present study evaluates the levels of complement components C3 and C4, C-reactive proteins, and IL-6 in patients who met DSM-III-R diagnostic criteria for major depressive disorder, as well as controls. Whereas no significant differences between the mean levels of C3 could be detected between depressed patients and controls, the levels of C4, IL-6 (where detected), and C-reactive protein were significantly raised in the group with a depressive disorder. Our study suggests an interaction between psychological state and immune systems operative in host defenses.

Experimental approaches to therapy and prophylaxis for heat stress and heatstroke

New developments in the fields of biochemistry, physiology, sepsis, cancer therapy, and molecular genetics have led to opportunities for the development of new therapies and prophylaxes for heat illnesses and for improving human performance during conditions of environmental stress. These include antilipopolysaccharide agents, anticytokines, potassium channel agents, a diet rich in omega-3 fatty acids, and psychological conditioning. This review summarizes the backgrounds and recent findings in the above fields and provides specific suggestions for potential therapy and prophylaxis for classic and exertional heatstroke and for improving athletic performance.

Major depressive disorder is associated with elevated monocyte counts

One of the most consistently reported findings in depression has been leucocytosis. In 33 in-patients with major depressive disorder, we assessed white blood cell count (WBC) and lymphocyte subsets four times over a period of 6 weeks. The control group consisted of 44 healthy subjects. Shortly after admission, we detected significant increases in the numbers of leucocytes, granulocytes, platelets and monocytes in the depressed patients. Patients who recovered well during hospitalization showed a decrease in monocyte counts, whereas those with slower clinical improvement had significantly higher monocyte counts than the control group. This longitudinal study demonstrates that monocytes may play a role in the acute phase of depression and could provide an explanation for immunological dysfunction in depressive states.

The immune system and major depression

This paper reviews research literature on the links between human immune functioning and mood disorders. It summarizes the initial steps of this fledgling research area since its inception in the late 1970s, and outlines a range of studies that are needed to increase our neuroimmunological sophistication. Future investigations will require greater specificity in several interrelated realms of inquiry: diagnostic, epidemiologic, and physiologic. In particular, this paper highlights basic physiological studies needed in both neurophysiology and immunology to provide a foundation for meaningful examination of their interface. Among the areas that require more specific investigation in both immunologic and mood disorders research is that of temporal organization. Just as psychiatric researchers have begun to scrutinize temporal cycles of mood, behavior, and neurophysiology, so too exploration of immune functioning must take into account predictable temporal cycles such as circadian and ultradian rhythms, as they shape responses to unanticipated external perturbations. Clarification of the temporal dimension will add significantly to our analysis of the links between immune functioning and mood disorders. The basic science of psychoneuroimmunology continues to mature, bringing new discoveries and revealing hitherto unknown mechanisms and interactions. This is a field of study in many ways still on the frontier, and explication of the long suspected links between mood disorders and immune functioning continues to beckon.

Lymphocyte subsets associated with major depression and dysthymia: modification by antidepressant treatment

Major depression and dysthymia (chronic, low grade depression) were associated with an increase in the number of CD16/56 (natural killer; NK) cells in blood, whereas other lymphocyte subsets (CD3, CD4, CD8, CD19, and the CD4/CD8 ratio) did not differ from control subjects. After treatment with a specific serotonin reuptake inhibitor, the symptoms of depression were alleviated in both the major depressive and dysthymic patients. Likewise, NK cell numbers declined to control values in these treated groups. Among the major depressive patients, the NK cell number reached control values within 4 weeks, whereas 6 months of treatment was required for such an effect to be achieved in the dysthymic patients. Although plasma levels of epinephrine, norepinephrine, cortisol, and ACTH were not different between groups, among the major depressive patients ACTH was inversely correlated with total lymphocytes, CD3, and CD19, and epinephrine was directly related to the CD4 and CD4/CD8 ratio. Among dysthymics, ACTH was unrelated to any of the lymphocyte subsets, but norepinephrine was directly related to total lymphocytes, CD3, CD4, and NK cells. The data are interpreted in terms of stress perception among major depressive and dysthymic patients and the potential impact of stressor experiences on immune processes.

The effects of the opiate antagonist naloxone on measures of cellular immunity during rest and brief psychological stress

This study investigated subjective, cardiovascular, and cellular immune system responses in 20 healthy young men during brief mental arithmetic stress compared with a video-watching control task. The role of endogenous opioids in mediating the immunological change to stress was examined by pre-task administration of the opiate antagonist naloxone. Immune changes were followed over a 1 hr post-task period. The results indicate significant physiological arousal and subjective distress as well as increases in NK cell cytotoxicity, numbers of circulating CD8 suppressor/cytotoxic T cells and NK lymphocytes following mental arithmetic but not the control task. Immune measures generally returned to baseline by 1 hr after the stress. Naloxone did not block the increase in NK cell activity or cell numbers following the stressor and had no effect on the other physiological or subjective measures. Thus, the results do not support endogenous opioids as a primary mechanism for immune changes to this type of acute stress. Naloxone did, however, increase NK cell cytotoxicity during the video task without effecting NK cell numbers, suggesting naloxone itself can increase per-cell NK cytotoxicity. Affective ratings for the week preceding testing were inversely related to the increase in NK cell numbers during mental arithmetic. If the increase in NK cell numbers under brief stress is part of an adaptive response to potential injury, then our data suggest that increases in general distress may impede normal immune system adaptation. Acute stress paradigms may be used as potential probes for investigations of individual differences in immune system responsivity.

Evidence for an immune response in major depression: a review and hypothesis

1. This paper reviews recent findings on cellular and humoral immunity and inflammatory markers in depression. 2. It is shown that major depression may be accompanied by systemic immune activation or an inflammatory response with involvement of phagocytic (monocytes, neutrophils) cells, T cell activation, B cell proliferation, an "acute" phase response with increased plasma levels of positive and decreased levels of negative acute phase proteins, higher autoantibody (antinuclear, antiphospholipid) titers, increased prostaglandin secretion, disorders in exopeptidase enzymes, such as dipeptidyl peptidase IV, and increased production of interleukin (IL)-1 beta and IL-6 by peripheral blood mononuclear cells. 3. It is hypothesized that increased monocytic production of interleukins (Il-1 beta and Il-6) in severe depression may constitute key phenomena underlying the various aspects of the immune and "acute" phase response, while contributing to hypothalamic-pituitary-adrenal-axis hyperactivity, disorders in serotonin metabolism, and to the vegetative symptoms (i.e. the sickness behavior) of severe depression.

Viruses, schizophrenia, and bipolar disorder

The hypothesis that viruses or other infectious agents may cause schizophrenia or bipolar disorder dates to the 19th century but has recently been revived. It could explain many clinical, genetic, and epidemiologic aspects of these diseases, including the winter-spring birth seasonality, regional differences, urban birth, household crowding, having an older sibling, and prenatal exposure to influenza as risk factors. It could also explain observed immunological changes such as abnormalities of lymphocytes, proteins, autoantibodies, and cytokines. However, direct studies of viral infections in individuals with these psychiatric diseases have been predominantly negative. Most studies have examined antibodies in blood or cerebrospinal fluid, and relatively few studies have been done on viral antigens, genomes, cytopathic effect on cell culture, and animal transmission experiments. Viral research on schizophrenia and bipolar disorder is thus comparable to viral research on multiple sclerosis and Parkinson's disease: an attractive hypothesis with scattered interesting findings but no clear proof. The application of molecular biological techniques may allow the identification of novel infectious agents and the associations of these novel agents with serious mental diseases.

Viruses, neurosis and fatigue

The evidence for viral infections as a cause of anxiety, depression and fatigue is reviewed. It is argued that in order to fully understand any proposed relationship the effects of psychosocial factors on immunity, convalescence and illness behaviour must be acknowledged.

Natural killer cell activity in major depression: relation to circulating natural killer cells, cellular indices of the immune response, and depressive phenomenology

1. Recently, blunted natural killer cell activity (NKCA) has been found in major depression. The present study investigates the relationships between ex vivo blunted NKCA in major depression, number or percentage of NKC, in vivo indices of systemic immune activation and depressive phenomenology. 2. Toward this end, NKCA, absolute number of leukocytes and number or percentage of lymphocytes, monocytes, neutrophils, activated T lymphocytes (HLA-DR+, CD25+) and NKC (CD3-CD56+) were determined in 13 normal controls and 36 depressed inpatients. 3. NKCA was significantly and positively related to number and percentage of NKC in the peripheral blood. The major depression-related reduction in NKCA was not related to alterations in peripheral NKC. There were significant negative correlations between NKCA and number or percentage of leukocytes, monocytes, neutrophils and HLA-DR+ T cells. Up to 50% of the variance in NKCA could be explained by the regression on the number of monocytes, percentage of HLA-DR+ T and NKC cells, and diagnostic classification. Up to 43% of the variance in NKCA was explained by depressed mood, somatic anxiety and less diurnal variation. 4. The results show that blunted NKCA in major depression is not related to alterations in peripheral NKC, but reflects in part the systemic immune activation in that illness.

Dysphoria and immune status in postpartum women

This study investigated the relationship between psychological factors and circulating immune cell populations in postpartum women. The study group was 75 women who had vaginal deliveries and were free of psychotropic medication. Four days postpartum each subject completed three mood questionnaires, and a small blood sample was taken. All questionnaire scores were shown to be highly inter-correlated and principal component factor analysis revealed a single factor which we term dysphoria. This factor was significantly associated with lower total circulating lymphocyte counts. The effect was strongest for T cells (largely attributable to a reduction in CD4+ ve T helper cells) and weaker for NK cell counts. No evidence was found of a mediating role for serum cortisol although serum cortisol levels were weakly related to immune status. This study has thus demonstrated that changes in the distribution of the lymphocyte pool are associated with relatively minor differences in postpartum affect.

The stress response and autoimmunoregulation

Using the recent burgeoning of information on how the stress response systems interact, and combining this with advances in our understanding of neuroimmune communication, a proposed neuroendocrine-neuroimmune stress response system incorporating autoimmunoregulation is reviewed. The study of immunocyte behavior in certain clinical conditions associated with a variant stress response may help illuminate the functioning of the neuroendocrine-neuroimmune stress response system.

Cytosolic free [Ca2+] in single T-lymphocytes from depressed patients and healthy controls

Human lymphocytes are widely used as peripheral models for central neurones. Alterations in immune function have been reported in depressed patients, e.g. mitogen-induced proliferation is impaired during depression. One possible causative mechanism could be altered [Ca2+]i regulation. Phytohaemagglutinin (PHA)-induced rise of [Ca2+]i has been found to be diminished in lymphocyte suspensions from depressed patients (Ecker et al., this issue). We measured PHA-induced rise of [Ca2+]i in single Fura-2 AM-loaded T11+ lymphocytes of patients with major depression and controls to further analyse [Ca2+]i regulation in depression. The [Ca2+]i of resting lymphocytes was 57 +/- 2 nmol/l (mean +/- SEM). There was no difference in resting [Ca2+]i of resting lymphocytes of patients and controls. PHA evoked an increase of [Ca2+]i an 7 out of 14 cells from control subjects up to 400-500 nmol/l. In contrast, only 4 out of 13 cells from depressed patients showed an increase of [Ca2+]i up to 200 nmol/l. In a small fraction of cells from both groups the [Ca2+]i signal is oscillating. Our preliminary data confirm alteration of [Ca2+]i regulation in lymphocytes of depressed patients.

Cytokine production in major depressed patients before and after clomipramine treatment

Cytokine production by peripheral blood mononuclear cells (PBMC) was assessed in 10 major depressed patients (5 men and 5 women) before and after 4 weeks of clomipramine treatment and in age- and gender-matched healthy controls. A significant reduction in interleukin-1B (IL-1B), interleukin-2 (IL-2) and interleukin-3-like activity (IL-3-LA) was observed in untreated depressed patients when compared to controls. IL-1B and IL-3-LA synthesis was significantly increased after drug treatment. The suppression of cytokine production by PBMC in depressed patients may be attributed to the depression per se, or it may be related to depression-associated hyperactivity of the hypothalamic-pituitary-adrenal axis. The mode of interaction between depression and cellular immune function and the mediators responsible for the reduced cytokine production need to be studied further.

Stress-induced immune suppression. Role of the autonomic nervous system

Experimental data together with clinical studies have generated information about the association between sympathetic nervous system activity and immunity as measured by in vitro correlates of cellular immune function. In addition, studies on the in vivo role of central CRF in coordinating sympathetic outflow and modulating immune function have provided an opportunity to examine central mechanisms important in the link between brain, behavior, and immune function. Finally, use of CRF as a neuropeptide probe will likely continue to give information about the central mechanisms relevant to the abnormal regulation of sympathetic nervous activity and immune function in stress and possibly in aging.

Depression, adrenal steroids, and the immune system

During the past decade, over 30 studies have examined the immune system in depression. While a number of investigators have reported depression-related alterations in peripheral blood immune cell number and function, many researchers have been unable to replicate these findings. The relationship between depression and the immune system has turned out to be much more complex than was initially anticipated. Factors which have complicated the interpretation of the research include the heterogeneity of depressed patients, the variability of immune assays, and the clinical relevance of these assays. In this review we conclude that alterations in the immune system do not appear to be a specific or reproducible biological correlate of depression but may occur in association with other variables which characterize depressed patients including age, sex and severity of depression. Conceptual frameworks for future research on the immune system and depression are discussed and include: (i) depression as a cofactor in the development, course and outcome of diseases involving the immune system; (ii) depression as a neuroimmunological disease; and (iii) depression as a model for studying neuroendocrine-immune interactions in humans. In terms of this third line of research, patients with depression consistently have been shown to display abnormalities in the secretion of adrenal steroids, and new data is presented which indicates that adrenal steroids may play a much more complex role in the modulation of the immune response than has been previously appreciated.

Relationships between interleukin-6 activity, acute phase proteins, and function of the hypothalamic-pituitary-adrenal axis in severe depression

Recent studies from this laboratory have provided some evidence that major depression, in particular melancholia, may be accompanied by an immune response. The present study was designed to investigate whether severe depression is characterized by increased interleukin-6 (Il-6) activity and whether Il-6 production is related to altered levels of acute phase reactants and to abnormal function of the hypothalamic-pituitary-adrenal (HPA) axis. Measurements were made in 8 healthy control subjects and 24 depressed inpatients of Il-6 production in culture supernatants of mitogen-stimulated peripheral leukocytes and plasma levels of haptoglobin (Hp), transferrin (Tf), and postdexamethasone cortisol. Il-6 activity was significantly higher in melancholic subjects than in healthy control subjects and in patients with minor depression or nonmelancholic major depression. Il-6 production was significantly correlated with Hp (positively) and Tf (negatively) plasma levels. There were significant and positive correlations between Il-6 activity and postdexamethasone cortisol values. The findings may suggest that increased Il-6 activity in severe depression is related to hypotransferrinemia, hyperhaptoglobinemia, and hyperactivity of the HPA axis.

Investigations of the cellular immunity during depression and the free interval: evidence for an immune activation in affective psychosis

1. Results of investigations of the immune function in affective disorders are conflicting. Some authors described an immune suppression, others an immune activation in major depression. The authors performed a study of cellular immunity in the MDD subtype endogenous depression. 23 patients suffering from endogenous depression were investigated during the depressive state, the results were compared with a group of 14 patients during the free interval and 51 healthy controls. 2. The lymphocyte proliferation after incubation with diphtheria- and tetanus toxoid, mainly stimulating T-cells, was reduced but after incubation with an antigen-cocktail, stimulating both, T- and B-cells, was increased in patients during depression and during the free interval compared to controls. 3. The CD3(+)- and CD4(+)-cells were significantly enhanced in both groups of patients while the CD8(+)-cells showed no differences to the controls. The ratio CD4+/CD8+ was increased in patients, too, as described in some autoimmune disorders. 4. The suppressor cell activity was significantly reduced in the PWM-assay and in the PHA-assay. The mixed lymphocyte culture showed a tendency to reduced suppressor cell activity as well. 5. The results point to an immune activation and to a disturbed control of the proliferative activity in affective psychosis. A T-cell related defect, not compensated by an increased number of CD3+- and CD4+ -cells is discussed. 6. From our point of view, the conflicting results of psychoneuroimmunological investigations in depressive disorders may be related to etiologically different subgroups of depression. The diagnostic category of MDD is possibly one of the traps in psychoneuroimmunology.

Cellular immunity, HLA-class I antigens, and family history of psychiatric disorder in endogenous psychoses

We found an increased lymphocyte proliferation after stimulation with an antigen "cocktail" in 49 schizophrenic patients and 37 patients suffering from affective psychosis, compared with 45 healthy control subjects. On the basis of this and other findings such as increased numbers of CD3+ and CD4+ cells, an increased ratio of CD4+/CD8+ cells, and a reduced level of suppressor cell activity in schizophrenia and endogenous depression, we investigated the influence of the human leukocyte antigen-Class I (HLA-A, HLA-B, HLA-C) system on the altered immune function and evaluated the relationship to immune function of a family history of psychiatric disorders. A cluster analysis of cases with regard to the HLA-Class I antigens was first performed in a group of 133 healthy control subjects, and two immunogenetically different clusters were found; then 86 patients (49 schizophrenics, 37 affective psychoses) for whom immune functional data were available were assigned to the two HLA-I clusters that had been determined in the control subjects. Analyses of variance (ANOVAs) showed no differences in immune function between the two clusters. With respect to the cluster assignment and the family history of psychiatric diseases, a two-way ANOVA revealed significant differences in the lymphocyte response to the antigen cocktail, in the number of CD8+ cells, and in one suppressor cell assay. When patients were compared by ANOVA on the basis of family history of psychiatric disorder, patients with a positive family history showed a significantly higher number of CD4+ cells and a higher CD4+/CD8+ ratio. Moreover, certain HLA genes, especially HLA-A1, HLA-B8, HLA-B16, and HLA-C2 seemed to be related to the immune function and/or to the immune function and the family history.

Urinary neopterin quantification indicates altered cell-mediated immunity in healthy subjects under psychological stress

In an effort to quantify changes in cell-mediated immunity (CMI) in healthy subjects under stress, we measured levels of neopterin, a well-validated marker of CMI activation, in the urine of medical students undergoing academic examinations. Neopterin/creatinine ratios measured on the first day of examinations (mean 46 mumol/mol) were significantly lower than those measured two weeks before (mean 78 mumol/mol, p = .004). Minimum neopterin production coincided with maximum subjective stress, as measured by a visual analogue scale. After examinations, neopterin/creatinine ratios rose (means 62 mumol/mol immediately after, and 65 mumol/mol two weeks after examinations), and these levels were not statistically different from those two weeks before examinations. Over this post-examination period, subjective distress was significantly lower than at either time point before examinations. We conclude that urinary neopterin/creatinine ratios may change significantly during periods of psychological stress, indicating concomitant alterations in CMI activation.

Depression and T lymphocytes in patients with irritable bowel syndrome

In 74 patients (23 male, 51 female) with irritable bowel syndrome (IBS) and in 15 matched control persons, an assessment of depression by means of the Zung Depression Self-Rating Scale (ZDS) and a determination of the number of total lymphocytes and T lymphocytes were carried out. In patients with IBS, the depression score was significantly higher than in controls. Among patients with IBS, the intensity of depressive symptoms did not relate to age, gender or to the type of the illness. IBS patients with a depression score on ZDS of 50 or more (31% of subjects) had a significantly lower number of total lymphocytes and T lymphocytes than the rest of IBS patients. The results may suggest a possible association between depression and indices of cellular immunity in IBS patients.

Psychomotor retardation, anorexia, weight loss, sleep disturbances, and loss of energy: psychopathological correlates of hyperhaptoglobinemia during major depression

Recently, we have established that major depression is characterized by hyperhaptoglobinemia, which may be regarded as an index of an "acute" phase response in that illness. The present study investigates the psychopathological correlates of increased plasma concentrations of haptoglobin (Hp) in major depression. To this end, the authors studied the Hp levels in relation to depressive items of the Structured Clinical Interview for DSM-III (SCID) and the Hamilton Rating Scale for Depression (HRSD) in 90 depressed subjects. There was a significant positive relationship between the SCID symptoms anorexia/weight loss, sleep, and psychomotor disorders and Hp plasma concentrations. Hp plasma levels were significantly and positively correlated with overall severity of illness (HRSD). The HRSD symptom correlates of higher Hp levels were loss of interest, middle insomnia, and psychomotor retardation. Up to 31.4% of the variance in Hp plasma values could be explained by psychomotor disorders, anorexia, weight loss, middle insomnia, and less diurnal variation of mood. It is suggested that hyperhaptoglobinemia, as an index of an "acute" phase response in major depression, is related to the somatic dimension of depressive illness.

Autoimmunity in depression: increased antiphospholipid autoantibodies

Some groups have recently reported higher titers of autoantibodies in depressed subjects than in normal controls. The present study investigates whether depressed patients exhibit increased antiphospholipid antibody titers compared with normal controls. The authors measured the binding index (BI) of antiphosphatidylserine (APSA), antipartial thromboplastin (APTA) and anticardiolipin (ACA) in 22 minor, 23 simple major and 20 melancholic depressives, 10 healthy controls and 104 normal controls with negative autoantibody sera. Depressed subjects exhibited significantly higher APSA and APTA antibody titers compared with normal controls. A large number of depressed subjects (+/- 54%) showed APTA and APSA positivity, defined as BI > or = 2 standard deviations above the mean BI of normal controls. There was a significant discrimination (> or = 2.8 standard deviations) between melancholic subjects and healthy controls with respect to BI of ACA, APSA and APTA. However, by using a more conservative value for phospholipid positivity (i.e., BI > or = 5 standard deviations above the mean BI of a reference sample of normal sera), the subject's autoantibody titers were, on the whole, within the normal range. Our results point towards a higher expression of antiphospholipid antibodies during depression but a much lower incidence of positive patients than in classical autoimmune disorders, such as systemic lupus erythematosus.

Immune disorders in depression: higher T helper/T suppressor-cytotoxic cell ratio

This study investigated the leukocyte T helper and T suppressor-cytotoxic cell (sub)set profile of minor, simple major and melancholic depressives versus normal controls. Using both monoclonal antibody staining and flow cytometry, we determined the absolute numbers and percentages of the following T cell immune subsets: T helper (CD4+), T virgin (CD4+CD45+), T memory (CD4+CD45-), T suppressor/cytotoxic (CD8+), CD8+ T suppressor (CD8+CD57-) and CD8+ T cytotoxic (CD8+CD57+) cells. After computing the CD4+/CD8+ ratio, we detected a significantly increased ratio in depressed patients as compared with healthy controls. Depression per se is characterized by a higher percentage of CD4+ and a lower percentage of CD8+CD57- cells. Melancholic depressed subjects exhibit a significantly increased number of CD4+ and CD4+CD45- cells. The combined use of various percentages of CD4+ and CD8+ (sub)sets yields a high degree of marker positivity for melancholia: through cumulative evaluation of those percentages, the marker positivity increases to 68% (sensitivity) and the specificity is 95%. These results together with our previous reports may refer to a depression-related state of T cell activation.

Neopterin measurement provides evidence of altered cell-mediated immunity in patients with depression, but not with schizophrenia

Neopterin is a validated marker of the activation of cell-mediated immunity in a variety of disease states. We measured neopterin and creatinine concentrations in the plasma and urine of 22 schizophrenic and 26 depressed patients admitted acutely to hospital, and compared results with those in a large group of normal controls. Neopterin/creatinine ratios were normal in the schizophrenic patients, but significantly elevated in the plasma of depressed patients. In each diagnostic group, the use of psychotropic drugs before admission had no effect on the neopterin ratios observed. Our findings indicate altered cell-mediated immunity in depression.

Neutrophil chemotaxis, phagocytosis, and superoxide release in depressive illness

Recently, some authors have reported defective neutrophil phagocytosis during depression. The present study investigated neutrophil function in 19 healthy controls and in 41 depressed inpatients categorized according to DSM-III into minor, simple major, and melancholic depression. We determined neutrophil function by means of phagocytosis, chemotaxis, and superoxide release. The results show no significant differences in neutrophil function among any of the subtypes of depression and normal volunteers. This suggests that overall neutrophil function is normal during depression. Thus, neutrophils are unlikely to be involved in the increased susceptibility to physical illness of patients with depression.

Leukocytosis, monocytosis and neutrophilia: hallmarks of severe depression

To date, there has been a small number of reports that severe depression is accompanied by disturbances in total white blood cell (i.e. leukocytosis) and leukocyte subset (i.e. neutrophilia, monocytosis, lymphopenia) counts. These results, however, have not yet been validated in a large-scale, well-controlled study. To this end, we have counted the number of leukocytes, monocytes, lymphocytes and granulocytes (neutrophils, eosinophils, basophils) in 22 healthy controls and in 109 depressed inpatients. We noted leukocytosis in major depressed patients compared with normal subjects, whilst minor depressives manifested intermediate findings. Leukocytosis was significantly more pronounced in major depressed males compared with major depressed females. Major depression related leukocytosis appears to be characterized by neutrophilia and monocytosis. There was a significant positive relationship between the overall severity of illness on one hand, and the degrees of leukocytosis, neutrophilia and monocytosis on the other. The total number of both phagocytic cell populations (i.e. monocytes and neutrophils) was significantly and positively related. Our results might point to the existence of an inflammatory process in major depressed subjects, particularly in males.

Evidence for a systemic immune activation during depression: results of leukocyte enumeration by flow cytometry in conjunction with monoclonal antibody staining

Several studies have reported a suppressed immune function (e.g. blast transformation) during depression. In an attempt to define the cellular basis of the reported immune disorders, the present study investigates the leukocyte cell subset profile of minor, simple major, and melancholic depressives, versus normal controls. We have counted the number of white blood cells (WBC) lymphocytes, monocytes, and granulocytes, while the number of lymphocyte (sub)populations has been identified by phenotype, using monoclonal antibody staining in conjunction with flow cytometry. The following cell surface antigens were determined: CD3+ (pan T), CD19+ (pan B), CD4+ (T helper/inducer), CD8+ (T suppressor/cytotoxic), CD4+CD45RA (T-memory cells), CD4+CD45RA+ (T-virgin cells), surface Ig, class II MHC HLA-DR, and CD25+ (IL-2 receptor). By means of pattern recognition methods, we established distinct immunological changes in minor and simple major depressed and in melancholic patients, setting them apart from the reference population. Depression, per se, is characterized by a higher number of WBC, monocytes, class II MHC HLA-DR, and memory T cells. Minor and simple major depressives exhibited an increased T helper/suppressor ratio. Increased numbers of IL-2 receptor bearing cells are a hallmark for major depression. Melancholics showed an increased number of pan T, pan B and T suppressor/cytotoxic cells. It was concluded that the established immune cell profile of depressed patients may point towards the existence of a systemic immune activation during that illness.

Immunological variability associated with experimentally-induced positive and negative affective states

Functional and phenotypic immunological parameters were examined immediately before, after, and 30 minutes after experimentally-induced short-term positive (happiness) and negative (anxiety, depression) affective states and a neutral state, in five healthy subjects. Results indicated that all affective states induced more immune fluctuations (regardless of the direction) than the neutral state. Furthermore, among the affective states, anxiety induced the most immunological variability and depression the least.

Cell-mediated immunity in patients with chronic fatigue syndrome, healthy control subjects and patients with major depression

The chronic fatigue syndrome (CFS) is characterized by severe persistent fatigue and neuropsychiatric symptoms. It has been proposed that the abnormalities in cell-mediated immunity which have been documented in patients with CFS may be attributable to a clinical depression, prevalent in patients with this disorder. Cell-mediated immune status was evaluated in patients with carefully defined CFS and compared with that of matched subjects with major depression (non-melancholic, non-psychotic) as well as healthy control subjects. Patients with CFS demonstrated impaired lymphocyte responses to phytohaemagglutinin (PHA) stimulation, and reduced or absent delayed-type hypersensitivity (DTH) skin responses when compared either with subjects with major depression or with healthy control subjects (P less than 0.05 for each analysis). Although depression is common in patients with CFS, the disturbances of cell-mediated immunity in this disorder differ in prevalence and magnitude from those associated with major depression. These observations strengthen the likelihood of a direct relationship between abnormal cell-mediated immunity and the etiology of CFS.

Reduced natural killer cell cytotoxicity in depression but not in schizophrenia

A reduction of natural killer (NK) cell activity has been found in hospitalized patients with major depressive disorder. To examine whether a reduction of NK activity is found in other psychiatric patients or related to the nonspecific effects of hospitalization, NK cell cytotoxicity was compared in hospitalized depressed patients, schizophrenic inpatients, and two groups of controls separately age matched to each patient group. NK activity was significantly (p less than 0.01) lower in depressed inpatients than control subjects. However, in the hospitalized schizophrenic patients values of natural cytotoxicity did not differ from controls. These findings suggest that reduced NK cytotoxicity in depression is independent of the effects of hospitalization.

The effect of lithium therapy on parameters thought to be involved in the development of autoimmune thyroid disease

This study has considered the effects of primary affective disorders and lithium therapy on a number of factors thought to be important in the development of autoimmune thyroid disease. These factors were examined in (a) controls with no history of any such disorders; (b) patients with primary affective disorders treated with drugs other than lithium and (c) patients with primary affective disorders treated with lithium alone. Eight of 40 patients who were receiving lithium therapy were found to be positive for thyroid microsomal and/or thyroglobulin antibodies, compared to only 3/40 patients who were receiving some other form of treatment for their depression. Peripheral blood mononuclear cells from patients receiving lithium were found to have significantly reduced numbers of suppressor/cytotoxic T cells (P less than 0.05). In addition, suppressor T cells from these patients showed a significantly reduced response to stimulation with concanavalin A (P less than 0.01). These effects were greatest in patients found to be antibody positive. Increased B cell activity, as measured by increased IgG and IgM release following mitogen stimulation, was seen in patients receiving lithium and in those patients receiving other forms of treatment for their depression. This would suggest that the increase is a feature of primary affective disorders and is not due specifically to lithium treatment. It would appear from this study that lithium therapy induces antibody formation in susceptible individuals and this may ultimately lead to the development of thyroid disease.

A further exploration of the relationships between immune parameters and the HPA-axis activity in depressed patients

In order to investigate the relationship between the immune apparatus and the hypothalamic-pituitary-adrenal (HPA)-axis activity in depressed patients, we measured in vitro lymphocyte responses to the mitogens Phytohaemagglutinin (PHA), Pokeweed (PWM) and Concanavalin A (Con A) and 8 a.m. baseline cortisol values in plasma, free cortisol excretion in 24 h urine (UFC), basal and post-dexamethasone beta-endorphin values. Major depressed patients with melancholia/psychotic features exhibited a significantly lower mitogen-induced blast transformation as compared to minor and simple major depressed patients. The lymphocyte responses to the three mitogens were significantly inversely related to baseline cortisol values and postdexamethasone beta-endorphin values. The proliferative capacity of lymphocytes to stimulation with PHA and PWM was significantly and positively related to UFC excretion. Up to 45% of the variance in the immune-responses to the mitogens was explained by the baseline cortisol, post-dexamethasone beta-endorphin and UFC values.

Biological measures and cellular immunological function in depressed psychiatric inpatients

Thirty depressed psychiatric inpatients, including 18 with a diagnosis of major depression, and 25 hospital staff controls were compared with respect to cellular immune function--that is, mitogen responsiveness to concanavalin A (con A), phytohemagglutinin (PHA), and pokeweed mitogen (PWM); natural killer cell (NK) activity; and T cell subsets, including helper/inducer T cells (CD4) and suppressor/cytotoxic cells (CD8). Only physically healthy subjects, who had not used psychoactive medications (except for low dose benzodiazepines) or other medications known to affect the immune system for at least 14 days, were included. Paired comparisons of the immune measures of patients with a DSM-III diagnosis of major depression (n = 18) with their controls demonstrated a statistically significant reduction of the patients' con A response. In addition, the patients with major depression had significantly lower con A and PHA responses than the combined patients with other forms of depression (atypical, dysthymic, or atypical bipolar). There was no indication that severity of depression, dexamethasone suppression test status, benzodiazepine use, or age accounted for the differences in immune function. A possibly important, unexpected finding was that antihistamine use was associated with lower immune function.