Is there immune dysfunction in depressive disorders?

Immunity and the pathophysiology of chronic fatigue syndrome

The pathophysiology of chronic fatigue syndrome (CFS) remains unknown. The syndrome often follows a recognized or presumed infection and the disorder may therefore result from a disordered immune response to a precipitating infection or antigenic challenge. Abnormalities of both humoral and cellular immunity have been demonstrated in a substantial proportion of patients with CFS. The most consistent findings are of impaired lymphocyte responses to mitogen and reduced natural killer cell cytotoxicity. Cutaneous anergy and immunoglobulin G subclass deficiencies have also been found. Further studies are needed examining cytokine levels in serum and cerebrospinal fluid, and cytokine production in vitro in patients with CFS. Interpretation of the findings of published studies of immunity is limited by probable heterogeneity in the patient groups studied, and by the lack of standardization and reproducibility in the assays used. The pattern of abnormalities reported in immunological testing in patients with CFS is consistent with the changes seen during the resolving phases of acute viral infection. These data provide circumstantial support for the hypothesis that CFS results from a disordered immune response to an infection. Longitudinal studies of immunity in patients developing CFS after defined infectious illnesses will provide the best means of further examining this hypothesis.

The relationship between distress and the development of a primary immune response to a novel antigen

Forty-five medical students were recruited to examine the effects of distress on the development of an immune response to the novel antigen, keyhole limpet hemocyanin (KLH). The subjects' level of distress was manipulated by immunizing them either at the time of an important viva voce examination (n=22) or during examination-free term time (n=23). This manipulation increased variance amongst the subjects, but the emphasis in this research was on individual distress as a predictor of immune function. In the group as a whole, the likelihood of developing DTH skin responses to KLH was reduced in the more distressed subjects (r=-.45; p=.002), independently of a number of behavioral (e.g., sleep disturbance) and demographic (e.g., sex) variables. Proliferation of T cells against KLH in vitro and the development of anti-KLH IgG antibodies were not related to levels of distress. Thus, cellular, rather than humoral, immune responses in vivo appear susceptible to the influence of distress. This immunization model provides the opportunity to further dissect the basis of these stress-immune pathways.

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.

Pre-operative [correction of Properative] psychological variables predict immunological status in patients with operable breast cancer

In a prospective study of psychobiological responses in patients with operable breast cancer, psychological data were collected one day before surgery and immunological data one day before and seven days after surgery.

OBJECTIVES

Explore psychoimmunological correlates related to primary surgical treatment of women with operable breast cancer.

METHOD

Distress was assessed with Impact of Event Scale (IES), depression with Montgomery-Aasberg Depression Rating Scale (MADRS), coping with Mental Adjustment to Cancer (MAC) scale, emotional suppression with Courtauld Emotional Control scale (CECS) and neuroticism with EPQ-N. Number of lymphocytes and subsets of lymphocytes were analyzed using a flow-cytometric method.

RESULTS

Intrusive anxiety and anxious preoccupation were statistically significant inversely correlated to number of lymphocytes, B, T total and T4 lymphocytes and depression to B and T4 lymphocytes using Bonferroni's correction for multiple testing. Multivariate analyses including menopausal status, type of surgery and health behaviour variables demonstrated an independent, inverse effect of depression on total number of lymphocytes, T total and T4 lymphocytes 7 days after surgery. Pre-post immune changes were influenced reversely by depression (decreased) and intrusion (increased).

CONCLUSIONS

Psychological parameters have a statistically significant impact on the number of lymphocytes and subsets of lymphocytes.

Clinical and subclinical hypothyroidism in patients with chronic and treatment-resistant depression

OBJECTIVE

To investigate the relationship between hypothyroidism and treatment-resistant depression (TRD).

METHOD

A retrospective case audit of 93 inpatients of a specialist Mood Disorders Unit. Patients referred with TRD were sub-classified into 'adequate' or 'inadequate' prior treatment groups on the basis of pre-established criteria, and compared with a 'non-TRD' control sample. Grades I (clinical) and II (subclinical) hypothyroidism were determined by review of relevant thyroid indices.

RESULTS

Patients had chronic depressive disorders (sub-group means of 57.5-82.2 weeks of illness). Of those patients referred with TRD, 22% (10/46) had evidence of clinical or subclinical hypothyroidism compared with 2% (1/47) of the non-TRD patients (p < 0.01). A gradient in the rates of grade I hypothyroidism was observed with the adequately-treated TRD patients having the highest rate (13%), the inadequately-treated TRD patients having an intermediate rate (7%), and the non-TRD patients having the lowest rate (2%). Consistent with this view, the inadequately-treated TRD group had the highest rate of grade II hypothyroidism (p = 0.01) and tended to have higher thyroid stimulating hormone (TSH) values (p = 0.06). Differences in the rates of hypothyroidism could not be accounted for by differences in age or prior exposure to lithium and/or carbamazepine. Duration of the depressive episode was negatively correlated with both the free thyroxine indices (r = -0.25, P < 0.05) and TSH levels (r = -0.32, p < 0.01).

CONCLUSIONS

This study suggests that relative hypothyroidism may play a role in the development of some treatment-resistant depressive disorders.

Depressive symptoms in the elderly: association with total white blood cell count

1. The white blood cell (WBC) count in those with high depressive symptoms and non-depressed participants in the Established Populations for Epidemiologic Studies of the Elderly (EPESE) were compared. 2. Of 3769 participants 10.8% had high depressive symptoms as assessed by the Centers for Epidemiologic Studies Depression (CES-D) Scale. The mean white blood cell count was higher in the high depressive symptoms group compared to the non-depressed group (6.8 +/- 0.12 x 10(9) WBC/1 and 6.5 +/- 0.03 x 10(9) WBC/1, respectively, p < 0.01). 3. Because older adults frequently have disabling chronic conditions which could both influence their leukocyte count and cause depressive symptoms, models were developed which controlled for the potential confounding. Even after adjusting for potential confounders, high depressive symptoms were still associated with higher white blood cell counts.

Delayed-type hypersensitivity skin testing: normal values in the Australian population

In our human psychoimmunological studies we have utilized a standardized assessment kit, the cell-mediated immunity (CMI) Multitest system, for determining delayed-type hypersensitivity (DTH) skin responses to a panel of ubiquitous antigens. Although the kit had been assessed in large populations of healthy controls in the U.S.A. and Europe, few data were available with regard to normative values in the Australian population. There are cogent reasons to suspect that results for the test will vary depending on geographical location, age cohort, compliance with specific immunization schedules and rates of natural exposure to certain diseases in differing populations. Most of our patient cohorts have a preponderance of female subjects and most standardization had been conducted in males. We tested medically and psychologically healthy males (n = 66) and females (n = 53). The percentage of positive responses to individual antigens was similar to other Australian studies but lower than that reported internationally. The mean number of positive responses was 3.7 for men and 2.8 for women, while the mean induration diameter was 17.5 mm for men and 12.2 mm for women. Three per cent of men and 5.6% of women were anergic (no positive responses), while a further 10.6% of men and 9.4% of women fell into the "hypoergic" category. These results, and those from other studies, indicate that the pattern of response to the CMI Multitest differs in healthy Australians. Therefore, researchers need to exercise caution when selecting patient and control samples (controlling for exposure factors), applying the test, reporting results (i.e. including all relevant parameters-with an emphasis on dimensional rather than categorical scores) and when designating subjects as having "impaired" responses.

Biochemical correlates of in vivo cell-mediated immune dysfunction in patients with depression: a preliminary report

We have previously demonstrated that at least 50% of patients with melancholia have impaired cell-mediated immunity (CMI) as assessed by delayed-type hypersensitivity (DTH) skin responses to a standardized battery of antigens. Hypercortisolaemia and increased circulating catecholamines both occur in patients with severe depressive disorders and each has been proposed as a possible mediator of observed immune abnormalities in patients with mood disorders. As part of a larger study, we collected 24 h urine samples from 28 patients with major depression and measured concentrations of urinary free cortisol (UFC), the noradrenaline metabolite dihydroxyphenylglycol (DHPG), adrenaline, and the dopamine metabolite DOPAC. CMI multitest skin testing revealed a reduced or absent response in 54% of subjects. Those with reduced DTH skin responses demonstrated increased urinary adrenaline (P < 0.02), with trends toward increased UFC (P = 0.052) and increased DHPG (P = 0.06). These differences could not be attributed to differences in age or depression severity. Correlational analyses demonstrated inverse associations between the extent of DTH responsiveness and 24 h levels of urinary adrenaline and DHPG, with similar trends evident for UFC and DOPAC. These results suggest that both circulating catecholamines and cortisol may play roles in the reduction of CMI in patients with severe depression.

Evaluation of immune parameters in depressed patients

The association between depression and altered immunological activities has repeatedly been suggested, but experimental data show contradictory results. In this work, cellular and humoral immunological activities were evaluated in patients presenting major depression, unipolar subtype. Natural killer cell activity (NKCA) was significantly reduced in patients as compared to healthy controls (p < 0.001). However, lymphocyte mitogenic responses and immunoglobulin titers (IgG, IgM, and IgA) were similar for all samples. Hematological, hormonal, and nutritional variables presented normal values in patients and in controls. A familial history of depression was related to lower NKCA and higher phytohemagglutinin responses (p < 0.01). These data suggest possible differential inhibition of cellular immune responses in depressed patients.

Natural killer cell activity in major depression: a prospective study of the in vivo effects of desmethylimipramine treatment

To evaluate NK activity changes associated with both the diagnosis of major depressive disorder (MDD) and the in vivo treatment of MDD with the tricyclic antidepressant desmethylimipramine (DMI), 15 MDD outpatients (11 females, four males) and eight controls (six females, two males) were evaluated prospectively at intake and after an average of 12 weeks of standardized DMI treatment. Plasma DMI concentrations at follow-up and severity of depression using the Extracted Hamilton Depression Rating Scale (EH) score at both intake and follow-up were also evaluated. At intake, NK activity was significantly higher in depressed patients compared to controls (P < 0.0001) while at follow-up NK activity was not different between the two groups. NK activity decreased from intake to follow-up in depressed patients but not in controls. A second analysis of NK activity was performed by dividing depressed patients into responders and nonresponders (EH > or = 8 at follow-up). At intake, there was no difference between responders and nonresponders while at follow-up NK activity was lower in nonresponders (P < 0.0001). Only nonresponders had a significant decrease in NK activity from intake to follow-up. No correlation was found between DMI blood level and NK activity, and no difference in NK activity was present between those with the highest and lowest DMI blood levels. Although it is apparent that both MDD and its treatment influenced NK activity in this study, it is unclear whether the decrease in NK activity in nonresponding patients was a function of persistent depressed mood and/or DMI treatment.

Cell-mediated immunity in combat veterans with post-traumatic stress disorder

OBJECTIVE

To explore immune function in patients with chronic post-traumatic stress disorder (PTSD).

DESIGN

A case-control study using the standardised Cell-mediated Immunity (CMI) Multitest.

PARTICIPANTS

Cases were 25 Vietnam combat veterans undergoing treatment for clinically diagnosed PTSD. Controls had no diagnosed psychiatric disorders: 28 were civilians and 20 were servicemen who had had South-east Asian postings but no combat experience.

MAIN OUTCOME MEASURES

The sum score, the number of reactions and the compound scores from the CMI Multitest were assessed as a measure of immune function.

RESULTS

Psychometric tests distinguished between cases and controls at a highly significant level (P < 0.001). Veterans with PTSD had enhanced cell-mediated immunity compared with civilians (P = 0.008) and servicemen (P = 0.02).

CONCLUSION

PTSD in combat veterans is associated with enhanced cell-mediated immune responsiveness. This could have wide implications for psychiatry and general medicine.

Impaired in vivo immune responses in patients with melancholia

Previous attempts to establish a relationship between impaired cell-mediated immunity (CMI) and major mood disorders have been limited by a failure to explore the relevance of depressive subcategories or to assess CMI by in vivo methods. In this case-control study CMI was assessed in 57 patients with major depression (31 with melancholic, 26 with non-melancholic disorders), and in age- and sex-matched controls by both in vitro and in vivo immunological techniques. Compared with control subjects and patients with non-melancholic depression, patients with melancholia demonstrated reduced in vivo CMI as assessed by delayed-type hypersensitivity (DTH) skin responses. Although increasing age, severity of depression, hospital admission for treatment, and reported weight loss are correlates of melancholia, none of these factors alone, or in combination, accounted for the differences in DTH responses observed between the two depressive subtypes. These data suggest that impaired CMI in vivo may be limited to those with melancholic disorders. At this stage the factors which account for this effect are unclear.

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.

Asymmetrical brain modulation of immune reactivity in mice: a model for studying interindividual differences and physiological population heterogeneity?

Functional brain asymmetry is associated with immune reactivity in mice. This association depends on the immunological parameters tested and on the sex and genetic background of animals. Each individual may be characterized by a paw preference score in relation with a particular immune pattern. The interindividual differences in immune reactivity connected with brain asymmetry give a new insight in the relation brain immunity and may represent a new aspect of population polymorphism.