Cerebral neocortex modulation of immune functions

Fifty Years of Handedness Research: A Neurological and Methodological Update

Handedness, a complex human aspect that reflects the functional lateralization of the hemispheres, also interacts with the immune system. This study aimed to expand the knowledge of the lateralization of hand, foot, and eye activities in patients with immune-mediated (IM) or other (noIM) neurological diseases and to clarify the properties of the Edinburgh Handedness Inventory (EHI) in an Italian population. Three hundred thirty-four patients with IM or noIM diseases affecting the brain or spine and peripheral nervous system were interviewed about stressful events preceding the disease, subjective handedness, and familiarity for left-handedness or ambidexterity. The patients and 40 healthy subjects underwent EHI examination. In the whole group of participants, 24 items of the EHI were classified into five factors (Hand Transitive, Hand Refined, Hand Median, Foot, Eye), demonstrating good reliability and validity. Chronological age had a significant influence on hand and foot EHI factors and the laterality quotient (LQ), particularly on writing and painting. In the patient groups, EHI factors and the LQ were also predicted by age of disease onset, duration of disease, and family history of left-handedness or ambidexterity. No differences were found between patients and healthy subjects, but pencil use scored significantly lower in patients with IM diseases than in those with noIM brain diseases. These results demonstrate that the lateralization of hand and foot activities is not a fixed human aspect, but that it can change throughout life, especially for abstract and symbolic activities. Chronic neurological diseases can cause changes in handedness. This may explain why, unlike systemic immunological diseases, IM neurological diseases are not closely associated with left-handedness. In these patients, the long version of the EHI is appropriate for determining the lateralization of body activities to contextualize the neurological picture; therefore, these findings extend the Italian normative data sets.

Abnormal cortical asymmetry as a target for neuromodulation in neuropsychiatric disorders: A narrative review and concept proposal

Recent advances in knowledge relating to the organization of neural circuitry in the human brain have increased understanding of disorders involving brain circuit asymmetry. These asymmetries, which can be measured and identified utilizing EEG and LORETA analysis techniques, may be a factor in mental disorders. New treatments involving non-invasive brain stimulation (NIBS), including trans-cranial magnetic stimulation, direct current stimulation and vagal nerve stimulation, have emerged in recent years. We propose that EEG identification of circuit asymmetry geometries can direct non-invasive brain stimulation more specifically for treatments of mental disorders. We describe as a narrative review new NIBS therapies that have been developed and delivered, and suggest that they are proving effective in certain patient groups. A brief narrative of influence of classical and operant conditioning of neurofeedback on EEG coherence, phase, abnormalities and Loreta's significance is provided. We also discuss the role of Heart rate variability and biofeedback in influencing EEG co-relates. Clinical evidence is at an early stage, but the basic science evidence and early case studies suggest that this may be a promising new modality for treating mental disorders and merits further research.

Immunological functioning in Alzheimer's disease: differential effects of relative left versus right temporoparietal dysfunction

The cerebral hemispheres are differentially involved in regulating immunological functioning and the neuropathology associated with Alzheimer's disease (AD) is asymmetrical. Thus, subgroups of AD patients may exhibit different patterns of immunological dysfunction. We explored this possibility in a group of AD patients and found that patients with low white blood cell counts and low lymphocyte numbers exhibited better performance on tests of right temporoparietal functioning. Also, a significant positive relationship exists between lymph numbers and performance on a test of left temporoparietal functioning. Thus, some AD patients have greater immunological dysfunction based on relative left versus right temporoparietal functioning.

The effect of hypnosis therapy on the symptoms and disease activity in Rheumatoid Arthritis

Abstract The present study aimed to assess the effectiveness of clinical hypnosis on the symptoms and disease activity of Rheumatoid Arthritis (RA). Sixty six RA patients participated in a controlled group design. Twenty six patients learnt the hypnosis intervention, 20 patients were in a relaxation control group and 20 patients were in a waiting-list control group. During hypnosis, patients developed individual visual imagery aimed at reducing the autoimmune activity underlying the RA and at reducing the symptoms of joint pain, swelling and stiffness. Subjective assessments of symptom severity and body and joint function, using standardised questionnaires and visual analogue scales, were obtained. Objective measures of disease activity via multiple blood samples during the therapy period and at the two follow-ups were also taken. These measurements were of erythrocyte sedimentation rate. C-reactive protein, haemoglobin and leukocyte total numbers. Results indicate that the hypnosis therapy produced more significant improvements in both the subjective and objective measurements. above relaxation and medication. Improvements were also found to be of clinical significance and became even more significant when patients practised the hypnosis regularly during the follow-up periods.

Relationship between neural activity and immunity in patients with undifferentiated somatoform disorder

It has been suggested that somatoform disorders are related to both the brain and the immune system, and that immune functions may be influenced by cerebral asymmetry. However, few studies have examined the relationship between brain activity and immune function in somatoform disorders. Thirty-two patients with non-medicated undifferentiated somatoform disorder were enrolled in this study. Blastogenic responses to phytohemagglutinin (PHA) were used to measure immunity. Regional cerebral perfusion was measured by 99m-Tc-ethyl cysteinate dimer single photon emission computed tomography (SPECT). Significant hypoperfusion was found at the left inferior parietal lobule and the left supramarginal gyrus in the more immune-suppressed (MIS) subgroup compared with the less immune-suppressed (LIS) subgroup. However, no regions of significant hyperperfusion were found in the MIS subgroup compared with the LIS subgroup. Decreased cerebral blood flow in the left inferior parietal lobule and the left supramarginal gyrus in the patient group was also significantly associated with reduced blastogenic responses to PHA regardless of sex and age. These results suggest that the left inferior parietal lobule and the left supramarginal gyrus might play an immunomodulating role in patients with undifferentiated somatoform disorder. In addition, these results suggest the role of cerebral asymmetry in altered immunity in the patients.

Handedness is associated with immune functioning and behavioural reactivity in rhesus macaques

In the present study we examined the relationship among handedness, immune functioning, and behavioural reactivity in rhesus macaques. We used the absolute number of CD4+ (T-helper) and CD8+ (T-suppressor) cells as dependent measures of immune functioning. We derived reactivity profiles from behavioural responses to a threat, and hand preference profiles from a quadrupedal food-reaching test. The results indicate positive correlations between the frequency of right versus left hand reaches and the absolute number of CD4+ cells, and between the frequency of right versus left hand reaches and the degree of human-directed aggression in response to an invasive threat. Immune measures were not associated with the strength of hand preference. These results are consistent with and extend previous findings obtained with rodents to nonhuman primates and provide further support for the view that behavioural lateralisation is associated with immune functioning and behavioural reactivity.

EEG source analysis of chronic fatigue syndrome

Sixty-one dextral, unmedicated women with chronic fatigue syndrome (CFS) diagnosed according to the Fukuda criteria (1994) and referred for investigation by rheumatologists and internists were studied with quantitative EEG (43 channels) at rest with eyes open and during verbal and spatial cognitive activation. The EEGs from the patients were compared with recordings from 80 dextral healthy female controls. Only those subjects who could provide 20 1-s artefact-free segments of EEG were admitted into the study. The analysis consisted of the identification of the spatial patterns in the EEGs that maximally differentiated the two groups and the estimation of the cortical source distributions underlying these patterns. Spatial patterns were analyzed in the alpha (8-13Hz) and beta (14-20Hz) bands and the source distributions were estimated using the Borgiotti-Kaplan BEAMFORMER algorithm. The results indicate that the spatial patterns identified were effective in separating the two groups, providing a minimum correct retrospective classification rate of 72% in both frequency bands while the subjects were at rest to a maximum of 83% in the alpha band during the verbal cognitive condition. Underlying cortical source distributions showed significant differences between the two groups in both frequency bands and in all cognitive conditions. Lateralized cortical differences were evident between the two groups in the both frequency bands during both the verbal and spatial cognitive conditions. During these active cognitive conditions, the CFS group showed significantly greater source-current activity than the controls in the left frontal-temporal-parietal regions of the cortex.

The effect of a naturalistic stressor on frontal EEG asymmetry, stress, and health

The aim of the current study was to investigate the effect of a naturalistic stressor, examination stress, on frontal EEG asymmetry, psychological stress, hormonal stress, and negative health. Forty-nine subjects were tested during periods of low and high examination stress. During the high examination stress period, subjects reported higher levels of stress on the Spielberger State Anxiety Inventory and Cohen's Perceived Stress Scale. However, no change in cortisol was detected across the two sessions. Furthermore, a shift from relatively greater left frontal activity during the low examination session to relatively greater right frontal activity during the high examination session was also found. Moreover, the increasing right frontal activity asymmetry associated with the high exam session compared to the low exam session correlated with increasing reports of negative health. No evidence was found for the prediction that cortisol mediated either the relationship between examination stressor and right frontal asymmetry or between right frontal asymmetry and negative health. In conclusion, while the findings from this study are compelling, the mechanism mediating increases in psychological stress, relatively greater right frontal activity, and increases in negative health from naturally occurring stressors is in need of further investigation.

Paw preference in dogs: relations between lateralised behaviour and immunity

Paw use in a task consisting of the removal of a piece of adhesive paper from the snout was investigated in 80 mongrel and pure-bred domestic dogs (Canis familiaris). Population lateralisation was observed, but in opposite directions in the two sexes (animals were not desexed): males preferentially used their left paw, females their right paw. The relationship between immune function and paw preference was then investigated. Some immune parameters (total number of white blood cells including lymphocytes, granulocytes and monocytes; leukocyte formula; total proteins; gamma-globulins) were investigated in a sample of left-pawed (n = 6), right-pawed (n = 6) and ambidextrous (n = 6) dogs. The results showed that the percentage of lymphocytes was higher in left-pawed than in right-pawed and ambidextrous dogs, whereas granulocytes percentage was lower in left-pawed than in right-pawed and ambidextrous dogs. Moreover, total number of lymphocytes cells was higher in left-pawed than in right-pawed and ambidextrous dogs, whereas the number of gamma-globulins was lower in left-pawed than in right-pawed and ambidextrous dogs. These findings represent the first evidence that brain asymmetry modulates immune responses in dogs.

Role of cerebral lateralization in control of immune processes in humans

Cerebral lateralization may be important in neural control of immune function. Animal studies have demonstrated differential effects of left and right brain lesions on immune function, but human studies are inconclusive. Here, we show that resections in the language dominant hemisphere of patients with epilepsy reduce lymphocytes, total T cells, and helper T cells. In contrast, resections in the language nondominant hemisphere increased the same cellular elements. T-cell responses to mitogens and microbial antigens were not differentially affected. Left/right arm histamine skin response ratios were altered in patients with left cerebral epileptic focus, and flare skin responses were reduced by left cerebral resections in contrast with an increase after right cerebral resections. The findings demonstrate a differential role of the left and right cerebral hemispheres on immune functions in humans.

Environmental stress mediates changes in neuroimmunological interactions

Combinations of environmental stress coordinately increase toxicological assaults on health, dependent on the genetics of the exposed organism. Multiple gene variances between individuals influence the risks associated with environmental exposures, and environmental stress presents in multiple forms including chemical, physical, and psychological stresses. Combined chemical, physical, and psychological stresses are suggested as exacerbating the initiation and/or duration of illnesses, and many of the detrimental outcomes on health are posited to relate to changes in neuroendocrine immune circuitry. However, most human epidemiological or experimental animal studies have not considered the combination of chemical, physical, and psychological stress on health status. Current consideration is being given to "real world" exposures for assessment of health risk, but this mainly relates to evaluation of chemical mixtures. In addition to concomitant chemical exposures having agonistic and/or antagonistic interactions, the physical and psychological status of the individual can influence exposure outcomes. An individual's psychosocial environment is likely to be important in epidemiological investigations. Neuroimmunology is a burgeoning discipline, and neurotoxicology and immunotoxicology studies should consider the bidirectional regulatory mechanisms between these organ systems and the potential long-term influences of psychological stress. This mini-review discusses some intriguing data from animal and human studies, which address the regulatory pathways between the neural, endocrine, and immune systems, with emphasis on psychological stress.

Cell-mediated immune hypersensitivity is stronger in the left side of the body than the right in healthy young subjects

More frequent appearance of herpes zoster infection on the left side of the body has been noted. In women, breast cancer occurs more frequently on the left side. It has been suggested that the left neocortex is involved in neuroimmunomodulation via the dopaminergic system. In this study, our purpose was to investigate the possible difference in cell-mediated hypersensitivity between right and left body sides using the tuberculin test with 22 male and 36 female healthy high school students. In the present study, the cell-mediated hypersensitivity was higher in the left side of the body than the right. This difference was slightly more apparent in the girls and may be related to brain asymmetry in neuroimmunomodulation.

Shamanism as a healing paradigm for complementary therapy

Any healing process--whether recovery from infection, physical trauma, or psychological distress--must entail the stimulation and direction of the body's own restorative functions. In former times these functions were called the vis mediatrix naturae. Arguably best articulated within traditional Chinese medicine (e.g. Reid 1993), many complementary therapies have identified this principle. The immune system is implicated in the operation of these healing processes, and immune system functions are modulated by both internal and external variables. External variables include the nature of the infection or trauma. Internal variables include the meaning of the illness to the patient or the patient's imagery surrounding the illness. It follows that any modulation of internal variables that increases immune function will therefore be highly beneficial in the healing process. Sometimes such modulation happens spontaneously, when it may be referred to as the placebo effect, or a good bedside manner, or spontaneous remission. Sometimes such modulation may be brought about intentionally either by the patient or by a therapist or healer. One body of technique for such modulation is shamanism, which pays particular attention to bridging the internal world of the patient to the external world where the problem originates. Shamanic practice is specifically focused on this healing task, and has its own toolkit of techniques for the modification of consciousness, the manipulation of imagery and meaning, and the generation of a healing milieu and therapeutic images from its mythic content. Early concerns about the mental health of shamanic practitioners are now thoroughly resolved (e.g. Stephen & Suryani 2000). Indeed, the relevance of shamanism to positive mental health is currently being explored (e.g. Money 1994, Singh 1999). Its relevance to social work (Voss et al. 1999) and to the near death experience (Green 1998) are also subjects of academic inquiry. The shamanic corpus exemplifies a healing paradigm that may also be used to understand the essential elements of healing, which underpin some established complementary therapies and some other healing modalities such as spiritual healing,'psychic' healing, spontaneous remission, and the placebo effect. The comparatively recent psychoneuroimmunological perspective appears to be congruent with and also to validate ancient shamanic healing technique. Both may share essential principles with complementary therapies and illuminate their essential healing processes.

Preclinical psychopharmacology of AIDS-associated dementia: lessons to be learned from the cognitive psychopharmacology of other dementias

Following a brief discussion of the epidemiology, underlying neuropathological mechanisms, neuropsychological symptoms and present treatment strategies of AIDS-associated dementia (AAD), parallels are drawn between the longer standing research on drugs for the treatment of other cognitive disorders, particularly senile dementia, and ongoing efforts to develop psychopharmacological approaches for the treatment of the cognitive impairments in AAD. Important aspects of hypotheses designed to guide such a research are indicated with the help of a speculative, paradigmatic hypothesis concerning the role of cortical cholinergic inputs in AAD. Furthermore, aspects of validity of animal models, and cognition as a crucial intervening variable in the effects of potential treatments, are evaluated.

Importance of immunological and inflammatory processes in the pathogenesis and therapy of Alzheimer's disease

The contribution of autoimmune processes or inflammatory components in the etiology and pathogenesis of Alzheimer's disease (AD) has been suspected for many years. The presence of antigen-presenting, HLA-DR-positive and other immunoregulatory cells, components of complement, inflammatory cytokines and acute phase reactants have been established in tissue of AD neuropathology. Although these data do not confirm the immune response as a primary cause of AD, they indicate involvement of immune processes at least as a secondary or tertiary reaction to the preexisting pathogen and point out its driving-force role in AD pathogenesis. These processes may contribute to systemic immune response. Thus, experimental and clinical studies indicate impairments in both humoral and cellular immunity in an animal model of AD as well as in AD patients. On the other hand, anti-inflammatory drugs applied for the treatment of some chronic inflammatory diseases have been shown to reduce risk of AD in these patients. Therefore, it seems that anti-inflammatory drugs and other substances which can control the activity of immunocompetent cells and the level of endogenous immune response can be valuable in the treatment of AD patients.

Prospective associations between lateralised brain function and immune status in HIV infection: analysis of EEG, cognition and mood over 30 months

Prospective relations between individual differences in both lateralised neuro-psychophysiological functions and mood ratings with immune status (CD4 and CD8 counts) were examined in asymptomatic HIV-positive men (n = 27) over thirty months. They participated in a controlled study of zidovudine versus placebo (results published elsewhere). Measures included EEG spectra, neuropsychological tests and mood ratings. A model of reciprocal lateralised influences on the immune system was tested whereby patients with left superior to right hemispheric functions were predicted to show a less deleterious outcome than those with the opposite asymmetry pattern. Prospective relations with immune status were found in the EEG with lateralised theta, alpha and beta activity; among cognitive measures with word fluency, semantic processing, and lateralised motor and recognition memory (word/face) processes; with mood ratings including depression, confusion and the total mood score. The nature of the effects supported the laterality predictions. These unique data, showing that neuro-psychophysiological factors in HIV+ but otherwise healthy subjects predict immune competence and compromise present 2-3 years later, warrant replication in a larger cohort.

Immunological changes in a case of Marchiafava Bignami disease: response to amineptine treatment

Marchiafava-Bignami disease (MBD) is a rare complication of chronic alcoholism. We describe a regressive form of MBD in which a primary decrease in CD4(+) cells was improved by amineptine treatment. No significant change in the CD4 : CDS ratio was observed in a few major depressed subjects receiving this drug.

Behavioral and immunological events induced by electrical stimulation of the rat midbrain periaqueductal gray region

We report here on the immunological and behavioral alterations induced by stimulation of the mesencephalic periaqueductal gray matter (PAG), a component of the brain aversive system. Male Wistar rats were implanted with stimulating electrodes in the caudal dorsolateral part of the PAG. After recovery, animals were screened for aversive behavior, characterized by running, jumping, vocalization or freezing reaction. Then, rats were subdivided to those which could control aversive stimulation (AS) by switch-off response (cAS group) and those which could not interrupt AS (uAS group). After sensitization with bovine serum albumin (BSA) in complete Freund's adjuvant, rats were stimulated 3 times/week for 40 days, each session lasting 30 min/rat. Immunological assessment included antibody production and hypersensitivity skin reactions to BSA 14 and 21 days after immunization. A behavioral profile of aversively stimulated animals was determined by a poststartle response, open field (OF) activity and two-way shuttle-box avoidance task. The results revealed elevated antibody production to BSA in cAS and lowered in uAS rats, compared to sham-stimulated and intact controls. Arthus and delayed hypersensitivity skin reactions increased in PAG-stimulated animals on day 14 but not on day 21 after immunization. Poststartle response was enhanced both in cAS and uAS rats. Along with immunopotentiation, administration of cAS produced hyperactivity in OF test and facilitation of the active avoidance learning, whereas uAS caused only moderate suppression of rearing in a novel OF environment. Physiological implications and possible mechanisms that may account for PAG-mediated immunobehavioral changes are outlined.

Hemispheric asymmetry in the effects of substantia nigra lesioning on lymphocyte reactivity in mice

Asymmetry in brain modulation of the immune system has previously been demonstrated at the neocortex level. In these experiments, the possibility of subcortical immunomodulation was investigated. In mice the substantia nigra was lesioned using the neurotoxin 6-hydroxydopamine. Four and six weeks after left or right lesions of the substantia nigra, spleen lymphocyte mitogenesis was slightly depressed or enhanced respectively as compared to sham operated controls. Differences appeared when comparing left and right lesioned groups. However, natural killer cell activity was unaffected by unilateral lesions of the substantia nigra. These results show that asymmetrical brain modulation may occur at the sub-cortical level and suggest that central dopamine is involved in neuroimmunomodulation.

Asymmetrical brain modulation of the immune response

It is now well known that the central nervous system can regulate the immune system. Interestingly the two sides of the brain have been demonstrated to be differently involved in the modulation of immune responses. In rodents, lesions of right or left neocortex induced opposite effects on various immune parameters including mitogen-induced lymphoproliferation, interleukin-2 production, macrophage activation or natural killer cell activity. Furthermore in humans, left-handedness has been reported to be associated with a high incidence of immune disorders. Likewise in mice, the direction of a lateralized motor behavior, i.e., paw preference in a food reaching task, correlated with an asymmetrical pattern of brain organization, was shown to be associated with lymphocyte reactivity, natural killer cell activity and auto-antibody production. Conversely the immune system could send to the brain information that may be asymmetrically expressed. The experimental models for investigating asymmetrical brain modulation of the immune system may be useful for studying physiological, pathological and genetic aspects of neuroimmunomodulation.

Lateralized rhythms of the central and autonomic nervous systems

This paper reviews lateralized ultradian rhythms in the nervous system and their unique place in evolutionary development. The rhythmic lateralization of neural activity in paired internal structures and the two sides of the central and autonomic nervous system is discussed as a new view for the temporal and spatial organization of higher vertebrates. These lateralized neural rhythms are integral to the hypothesis of the basic rest-activity cycle. Rhythms of alternating cerebral hemispheric dominance are postulated to be coupled to oscillations of the ergotrophic and trophotrophic states. The nasal cycle is coupled to this cerebral rhythm. This lateralized central and autonomic rhythm is discussed in relationship to ultradian rhythms of neuroendocrine activity, REM and NREM sleep, lateralized rhythms of plasma catecholamines, and other lateralized neural events. The relationship of this phenomenon to stress and adaptation is postulated. The effects of unilateral forced nostril breathing is reviewed as a method to alter cerebral activity, cognition, and other autonomic dependent phenomena.

Functional brain asymmetry and lymphocyte proliferation in female mice: effects of right and left cortical ablation

Brain immunomodulation may be lateralized as evidenced by two experimental approaches. Using a behavioral paradigm, we have reported an association between asymmetrical brain function and lymphocyte reactivity in mice selected for right- and left-paw preference. Left-handed mice, in comparison to right-handers, exhibit higher mitogen-induced T-lymphocyte proliferation. Using a cortical lesion paradigm in mice, it has been previously shown that each hemicortex modulates in opposite directions lymphocyte reactivity. In these experiments, the role of the brain cortex in the association between paw preference and immune reactivity was assessed by studying mitogen-induced lymphoproliferation in left- and right-handed mice after right or left-cortical ablation. The difference in T-lymphocyte responsiveness between right- and left-handed mice persisted after right lesions but was abolished after left lesions. This immunological effect of left cortical ablation is hypothesized to involve the hypothalamic dopaminergic neurons.

Lesions of the medial septal nucleus produce a long-lasting inhibition of T lymphocyte proliferation

The influence of the central cholinergic system on the immune system was studied in Wistar rats by lesioning the medial septal nucleus. This lesion inhibited T cell proliferation of splenocytes and thymocytes induced by the mitogens concanavalin A (Con A), phytohemagglutinin (PHA) and pokeweed mitogen (PWM) up to 25 days and did not affect proliferation at 40 days after lesioning. In contrast, the response to the B cell mitogen lipopolysaccharide from E. coli (LPS) was not affected at any time. These findings suggest a regulatory role of the cholinergic medial septal nucleus on T lymphocyte proliferation.

Asymmetrical effects of cortical ablation on brain monoamines in mice

Neurochemical changes induced by right or left cortical ablation which have previously been described to have immunological effects were investigated in mice. Catecholamine and indolamine levels were determined in the contralateral cortex and in subcortical structures involved in immunoregulation 14 and 60 days after unilateral cortical ablation. Unilateral cortical ablation induced profound and widespread changes in the contralateral cortex but also in subcortical regions of both sides at 14 days after surgery. Lesions of the left neocortex appeared mainly to affect the activity of serotoninergic inputs to the right neocortex, whereas ablations of the right cortex influenced the activity of the catecholaminergic inputs to the left. Sixty days after surgery, modifications in monoamine levels were observed only in the ipsilateral, but not contralateral, subcortical regions, the only exception being that DA turnover in the tuberoinfundibular system remained lowered in both hemispheres after either right or left cortical ablations. Furthermore, some asymmetrical effects of cortical lesions depended on functional brain lateralization as assessed by paw preference. It may be hypothesized that some neurochemical modifications induced by unilateral cortical lesions are, at least partially, responsible for the immunological perturbations observed after cortical ablation.

Immune function in lines of mice selected for high or low degrees of behavioral asymmetry

Cerebral lateralization has been suggested to play a regulatory role in immune function. In this study, several measures of immune function were evaluated in mice selectively bred for either a strong (HI) or weak (LO) degree of behavioral asymmetry (paw preference) and compared to an unselected control population (HET). Both HI and LO animals had fewer spleen cells but higher degrees of [3H]thymidine incorporation into DNA (on a per cell basis) than HET mice. However, only HI mice had lower immune functions compared to HET controls manifest as reduced mixed leukocyte reaction (MLR), cytotoxic T lymphocyte (CTL) activity, and natural killer (NK) cell activity. These findings indicate that although both extremes in the degree of paw preference may be associated with deviations from the norm, a high degree of behavioral lateralization is associated with decreased immune responsiveness in this animal model.

The nucleus basalis is involved in brain modulation of the immune system in rats

Male rats were subjected to bilateral or unilateral excitotoxic lesions of the nucleus basalis magnocellularis (NBM). Three weeks after surgery, mitogen-induced lymphoproliferation and natural killer (NK) cell activity were determined in the spleen. T-cell mitogenesis and NK cell activity were strongly enhanced after bilateral lesions but were not affected after right or left unilateral lesions. B-cell mitogenesis and blood T-cell subset distribution remained unchanged after bilateral or unilateral lesions of the NBM. These results demonstrate that NBM cells are involved in the complex interrelations existing between the central nervous system and the immune system.

Physiological basis for neuroimmunomodulation

A large number of clinical and experimental observations indicate that immune responses may be modulated by the central nervous system (CNS). The immune system (IS) and CNS are known to communicate via the endocrine and the autonomic nervous systems. In this overview, we will focus on the immunomodulating role of neurotransmitters and neuropeptides. Immune cells appear to express membrane antigens similar to those of neural cells. Similarities re-enforce analogies between CNS and IS cells. The concept that the CNS modulates immune functions implies that the immune system feeds back information to the CNS. In fact, interleukins have neuroendocrine functions whether they are produced at the periphery by immune cells or at the CNS level by glial cells. Finally, the possible endocrine functions of lymphocytes are described and it is suggested that a complete regulatory loop between immune and neuro-endocrine systems exists. Studies in neuro-immunomodulation are of great importance from a theoretical point of view, the CNS-IS inter-relationships may not be considered only between the CNS and the periphery but also at the level of the immune micro-environment which may be considered as an immune-neuro-endocrine complex.

Lymphocyte homing after left or right brain neocortex ablation

The cerebral neocortex is known to modulate the immune system in an asymmetrical way. Ablations of the left cortex decrease, whereas symmetrical right lesions have no effect, or enhance, T cell functions measured 6-8 weeks after lesioning. However, modifications of immune responses induced by lesions of the brain neocortex could result from a lymphocyte redistribution mediated by glucocorticoids, like that observed during stress. We tested this possibility in the present experiments. Cortical lesions modulated concanavalin A-induced proliferation of both lymph node and spleen lymphocytes in a similar way. Cortical lesions of either side modified neither the lymphocyte distribution of 51Cr-labelled injected lymph node cells, nor the percentage of blood cell subsets. These results show that cortical lesions do not affect lymphocyte homing, and suggest that the brain neocortex immunomodulatory effects are not mediated by glucocorticoids.

Freund's complete adjuvant induces ornithine decarboxylase activity in the central nervous system of male rats and triggers the release of pituitary hormones

In male rats, inoculation of Freund's complete adjuvant (FCA, 0.5 mg/rat of Mycobacterium butyricum in paraffin oil) induced high levels of ornithine decarboxylase (ODC) in the hypothalamus and pituitary gland (285% and 245% of controls, respectively, within 12 h to 2 days). ODC activity also was altered in the cerebellum and left neocortex, but not in the right neocortex. This activity reflected a dynamic equilibrium which is influenced by ODC synthesis, degradation, activation, etc. The circadian rhythms of pituitary ODC activity and plasma prolactin level, 3-4 days after FCA, showed that enhancement of enzymatic activity during the dark phase correlated with a marked release of prolactin (Prl). During this early period after FCA, changes in plasma levels of other pituitary hormones were not significant or were less important. Pretreatment with bromocriptine microcapsules inhibited both basal and FCA-induced pituitary ODC activity, as well as Prl secretion. Further, significant increases in plasma luteinizing hormone and adrenocorticotropic hormone were noted from days 4 and 8, respectively, and onwards. Finally, a phase of reduced corticosterone secretion occurred during the latency period. This study shows that FCA influences central nervous system pathways and supports the idea that endogenous Prl is involved in some early events which lead to the development of adjuvant arthritis.

Association between left-handedness and allergy: a reappraisal

There are conflicting reports in the literature about the possible association between left-handedness and immune disorders, including autoimmune diseases as well as allergies. In this study we compared the distribution of right- and left-handers, assessed with the Edinburgh Handedness Inventory, in a group of patients consulting an allergy clinic and a control population with a similar sex and age distribution. There was no overall association between left-handedness and allergies, although we found a tendency towards left-handedness in patients whose allergic symptoms started before puberty, suggesting that left-handers may have an increased predisposition to allergic disease that manifests itself during early life.

Functional brain asymmetry and murine systemic lupus erythematosus

The role of brain lateralization in antibody production was studied in a murine systemic lupus erythematosus model. Male and female New Zealand black mice that spontaneously produce pathogenic auto-antibodies directed against red blood cells and DNA, were divided into right- and left-handers using a paw preference test, and anti-erythrocyte and anti-DNA antibody production was repeatedly determined. In females, antibodies against erythrocytes and double-stranded DNA appeared earlier in left-handers. These results provide the first evidence of an association between a functional brain asymmetry and auto-antibody production and suggest the involvement of the central nervous system in the pathogenesis of autoimmune processes.

Brain neocortex modulation of mitogen-induced interleukin 2, but not interleukin 1, production

Interleukin 2 (IL-2) production by splenic T cells stimulated by Concanavalin A was studied in mice after unilateral or bilateral brain neocortex ablation. The brain cortex was shown to modulate IL-2 production in an asymmetrical way. IL-2 levels were higher in animals with a right cortical lesion (group R) and lower in mice with a symmetrical lesion (group L) as compared to controls, differences between groups R and L being significant. Such variations of IL-2 production that were observed after unilateral lesions were abolished with bilateral cortical ablations. These results extend the immunoregulatory roles of the brain neocortex to IL-2 production by splenic T cells and may provide molecular support for neuro-immunological networks.

Hemispheric asymmetry in the effects of cerebral cortical ablations on mitogen-induced lymphoproliferation and plasma prolactin levels in female rats

Female rats were subjected to unilateral left or right, bilateral, or sham ablation of the cerebral cortex. Eight weeks after surgery, the rats were sacrificed by decapitation and spleen cells were grown in culture for 96 h in the presence or absence of the T-cell mitogen concanavalin A or the B-cell mitogen lipopolysaccharide. Mitogenesis was determined by the addition of [3H]thymidine 24 h prior to harvesting. Both T- and B-cell mitogenesis were significantly depressed in subjects bearing cortical ablations in the right hemisphere, whereas left hemisphere ablation was without reliable effect. Prolactin in plasma collected at sacrifice was elevated in rats bearing right but not left hemisphere ablation and was significantly negatively correlated with both T- and B-cell immune responses. These results demonstrate a lateralized modulatory influence of cerebral cortex on immune function in female rats and they implicate elevated prolactin levels as a possible mediator of this effect.

Brain neocortex immunomodulation in rats

The influence of the cerebral neocortex on the immune system was studied in groups of male Wistar rats after lesioning the right or the left fronto-parietal cortex. In left-lesioned rats, mitogenesis of T-lymphocytes induced either by phytohemagglutinin or Urtica Dioca Agglutinin was depressed by about 25-40% as compared to controls. In contrast, T-cell mitogenesis in animals with right lesions, was enhanced by about 20-45% as compared to controls and by about 90% as compared to that observed in left-lesioned animals. Cortical lesions of either side were shown not to modify antibody synthesis and plasma levels of ACTH, or prolactin. These results, quite similar to those that we have previously observed in female mice, suggest that lateralization in brain cortex immunomodulatory functions may exist in both sexes and in several species of mammals.

Brain modulation of the immune system: association between lymphocyte responsiveness and paw preference in mice

An association between handedness and immune disorders has been described in man, left-handers being more susceptible to autoimmune or allergic diseases. However, this correlation was established between handedness and clinical signs of immune disorders without studying immune functions. Using an animal model, we demonstrated for the first time an association between handedness and lymphocyte reactivity. Left-handed mice were shown to exhibit higher mitogen-induced T lymphocyte proliferation than right-handed animals.

Early effects of right or left cerebral cortex ablation on mitogen-induced spleen lymphocyte DNA synthesis

The cerebral neocortex has been shown to modulate the immune system in an asymmetrical way. In mice, ablation of the left cortex decreases whereas a symmetrical right lesion enhances B and T cell-mediated responses measured at 6-8 weeks after lesioning. In order to study the possibility of neuronal reorganisation during the post-operative period, immunological parameters were determined as early as 2 weeks after right or left cortical ablation. Right lesions depressed lymphocyte DNA synthesis induced by concanavalin A (ConA) and phytohemagglutinin whereas left lesions only depressed ConA-induced blastogenesis. Right or left lesions had no effect on lipopolysaccharide-induced proliferation of B lymphocytes as well as on serum antibody levels. Comparisons between early and late effects of right or left cortical ablation on the immune system showed that each hemicortex differentially modulates lymphocyte subpopulations but also that the neuronal reorganisation following surgery can be different according to the side of cortex lesion.