Association between left-handedness and allergy: a reappraisal

Brain asymmetry, immunity, handedness

The principle of symmetry-asymmetry is widely presented in the structural and functional organization of the nonliving and living nature. One of the most complex manifestations of this principle is the left-right asymmetry of the human brain. The present review summarizes previous and contemporary literary data regarding the role of brain asymmetry in neuroimmunomodulation. Some handedness-related peculiarities are outlined additionally. Brain asymmetry is considered to be imprinted in the formation and regulation of the individual’s responses and relationships at an immunological level with the external and internal environment. The assumptions that the hemispheres modulate immune response in an asymmetric manner have been confirmed in experiments on animals. Some authors assume that the right hemisphere plays an indirect role in neuroimmunomodulation, controlling and suppressing the left hemispheric inductive signals.

Anomalous brain dominance and the immune system: do left-handers have specific immunological patterns?

Geschwind and Behan (1982) and Geschwind and Galaburda (1985a, 1985b, 1985c) suggested a correlation between brain laterality and immune disorders. To test whether this hypothesis holds true not only for the frequency of immune diseases and circulating autoantibodies, but extends also to cellular immunity, we examined the association between handedness and markers of cellular immunity. Twenty-seven left-handed and 37 right-handed subjects were serologically screened for cellular parameters and 22 left-handed subjects were typed for human leukocyte antigen (HLA). When compared to the right-handers, the left-handed group showed a significant decrease in the inflammatory cell types CD3(+) T cells (total T cells), CD4(+) T cells (T-helper cells), and HLA-Dr (MHC-II, antigen-presenting cells) as well as in the CD19(+) cells (B cells) and CD16/CD57(+) cells (natural killer cells). We assume a relationship exists between cerebral hemispheric specialisation and the immune system not only for humoral but also for cellular immunity, and we discuss the role of the major histocompatibility complex in neurological and immunological development.

Handedness and health: An examination of the association between different handedness classifications and health disorders

The current study investigated the incidence of various health disorders in a sample population of undergraduate students, using a 25-item hand preference questionnaire. Analysis revealed significant differences existed in the incidence of several health disorders as a function of handedness: however, these differences depended on how hand preference was defined. Overall, the results showed that non-right-handed participants (i.e., those individuals with left-handed, ambidextrous, or inconsistent hand preferences) were significantly more likely to report specific health disorders (such as high blood pressure and epilepsy) than right-handed participants. The findings provide support for the argument that left-handedness, or non-right-handedness, is associated with various health disorders. The results are discussed in light of the Geschwind-Behan-Galaburda model of cerebral lateralisation.

Fetal sensitivity to testosterone, left-handedness and development of bronchial asthma: a new approach

In contrast to Geschwind, Behan and Galaburda (GBG) theory, there is strong evidence that inheritance through maternal line is responsible for the coexistence of asthma and left-handedness early in childhood. A new model that incorporates GBG's theory and maternal inheritance is proposed. This hypothesis suggests that maternal atopy is the most important factor in the evolution of asthma and that GBG's theory applies mainly in childhood. An inherited enhanced sensitivity of fetus to testosterone may be the underlying mechanism that leads to the development of bronchial asthma.

Academic achievement and learning abilities in left-handers: guilt or gift?

The main purpose of this cross-sectional study was to compare the acceptance rate (AR) of left-handers (LHs) with that of right-handers (RHs) in the college entrance examination (CEE) for the national universities in Iran. During 5 successive years, fifty thousand participants in this exam were randomly sampled. We evaluated the relationships between AR and hand preference, sex, college admission (CA), entrance exam score (EES) and study areas: Mathematics, Natural Sciences, Humanities and Art. The acceptance rate of the LHs over the entire study period was significantly higher than that of the RHs (27.3% versus 24.3%, p < 0.0001). The mean score attained on examination by LHs was significantly higher than that of RHs in all study areas (p < 0.002). The acceptance rate of LHs in all study areas was higher but the difference reached statistical significance in the Art area only (p < 0.01). It is concluded that left-handers may be regarded as a heterogeneous large group consisting of different subgroups. Those who are able to compete for the college entrance examination score are even more successful than right-handers in terms of average EES and the rate of CA.

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.

Left-handedness and inheritance of bronchial asthma

A statistically significant difference in mean laterality quotients of 15 asthmatic and 106 nonasthmatic children showed a coexistence of left-handedness and asthma early in life. It is suggested that this phenomenon is not only a fetal event as the Geschwind-Galaburda hypothesis claims but it is mainly based on maternal line inheritance.

Relationship between left-handedness and allergic symptomatology

Handedness and health parameters were assessed in 70 infants. Video recordings were employed for handedness analysis. The infants' growth and health were periodically followed up from birth and information was retrieved from medical records. A significant association between left-handedness and allergy score was found (P < .05). Age (P < .02) and sex (P < .01) appear to be significant covariates. It appears that the possible association between left-handedness and immune-based diseases among adults applies to infants as well. A possible biologic marker for allergy should be incorporated in future research.

Associations among familial sinistrality, allergies, and developmental language disorders

Here we report the results of a study that tested what has become known as the Geschwind hypothesis (Geschwind & Galaburda, 1987). This study involved 526 people who were tested by an allergist for IgE-mediated allergies and who filled out a 12-item handedness questionnaire that also included questions about eyedness, prevalence of left-handedness in the immediate family, and familial developmental language problems. A series of log-linear analyses revealed that if the definition of "anomalous" included left-handedness and having a first-order left-handed relative, one was indeed more likely to be allergic than were those not so classified. When the definition of anomalous simply included those classified as left-handed, the results were not significant. Parallel findings resulted when the criterion variable was the presence of developmental language disorders. No evidence was found for relations between allergies and developmental language problems.

Ambilaterality: definition from handedness preference questionnaires and potential significance

Defining handedness according to the results of preference questionnaires is operational. Most often, handedness is defined according to the extremes of the handedness range or equal divisions of the entire handedness range. These definitions may exclude ambilateral (ambidextrous) subjects from analysis or may fail to separate out subjects with intermediate handedness scores. Examples from the literature are presented to show that subjects with handedness scores in the weak right-handedness range may have characteristics that distinguish them from subjects in other segments of the handedness spectrum. Handedness studies should assess the middle handedness range using a scoring method which identifies subjects in this range.

Handedness in women with intrauterine exposure to diethylstilbestrol

Completed forms containing the Edinburgh handedness inventory were received from 77 women exposed to diethylstilbestrol (DES) in utero. Laterality scores (LSs; range: -100 to +100) were calculated for each respondent based on the handedness inventory and were compared with LSs from 514 female controls. The handedness distribution in the DES daughters was significantly shifted away from strong righthandedness compared with the handedness distribution in the controls (chi-square = 22.0, P < 0.0001). Possible explanations for the association between handedness and DES exposure are presented, and aspects of handedness measurement are discussed.

Handedness, symptom reporting, and accident susceptibility

A cross-sectional design was used to examine the relationship among handedness, self-reported symptoms, and accident susceptibility in a nonclinical sample (N = 285). Left-handedness was not found to be associated with elevated symptom reporting (and, consequently, health problems) and accident susceptibility. Thus, the present findings do not support the hypothesis that left-handedness is accompanied by reduced physical fitness or accident proneness.

Gender, laterality, learning difficulties and health problems

This paper examines the association between self-reported laterality, learning difficulties and health problems. Responses to questionnaire data were obtained from 3829 males and 3631 females. Males reported increased cardiovascular disease, ulcers, and diabetes. Learning problems were increased in males, nonright-handers and those with a left eye preference. The highest proportion of difficulty learning to read was in males who were nonright-handed and right-eyed. Mixed dominance, however, did not fully explain the results since nonright-handers with left eye preferences had the next highest rate.

Brain lateralization and immunomodulation

The two sides of the brain may be differently involved in the modulation of immune responses as demonstrated by lesional and behavioral approaches 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. This animal model, useful to elucidate whereby the brain and the immune system can communicate, appears to be suitable for studying the immune perturbations observed during stroke in humans. Brain asymmetry in modulation of immune reactivity may also be demonstrated in intact animal using a behavioral paradigm. The direction of a lateralized motor behavior ie paw preference in a food reaching task, correlated with an asymmetrical brain organization, was shown to be associated with lymphocyte reactivity, natural killer cell activity and auto-antibody production. The association between paw preference and immune reactivity in mice varies according to the immune parameters tested and is a sex-dependent phenomenon in which genetic background may be involved. The experimental models for investigating asymmetrical brain modulation of the immune system should be useful for studying several physiological, pathological and genetic aspects of neuroimmunomodulation.

Neurology of developmental dyslexia

Developmental dyslexia was until recently considered to belong solely in the domain of educational psychology. With the advent of better theories on language and reading, and better methods for assessing the structure and function of living human brains and for determining genetic transmission, dyslexia is now poised to become a focal concern of cognitive neuroscience, neurology, and genetic research. Still unresolved are questions relating to how much a reading disability represents a normal variation or a separate pathological entity, and whether the cognitive disorder is primarily cognitive, or secondary to a disorder in early perception. Recent findings from neuroanatomy, neurophysiology, neuropsychology, and genetics research are reviewed. (This review is an updated version of a review first published in Current Opinion In Neurology and Neurosurgery 1992, 5:71-76.)

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.

Reading disability, immune disorders and non-right-handedness: twin and family studies of their relations

Geschwind and colleagues discussed associations among learning disorders, immune disorders and non-right-handedness. In this study, we examined the associations between reading disability (RD) and both immune disorders (ID) and non-right-handedness (NRH) in family and twin samples (total N = 1731 cases) identified through an RD proband. We also conducted co-segregation analyses to ascertain the degree to which NRH, ID and RD were biologically related. There was little evidence for an overall association between RD and NRH. There was not convergent evidence across all four samples for an association between RD and ID, although we did find an association between RD and ID in two of four samples. Nor was there strong support for a subtype where RD and NRH, or RD and ID, co-segregate in families. These data suggest that the associations postulated by Geschwind and colleagues are not robust in RD samples, although we cannot completely rule out the possibility of an RD plus ID subtype.

Early effects of unilateral lesions of substantia nigra on immune reactivity

It has recently been demonstrated that central dopaminergic pathways are asymmetrically involved in the modulation of the immune response. Mitogen-induced proliferation of T lymphocytes was shown to be enhanced 4-6 weeks after right lesion of the substantia nigra (SN) in mice, when compared to left lesioned and control animals. In order to study the involvement of post lesion neuronal reorganization in these results, the same immunological parameters were determined as early as 2 weeks after right or left lesion of the SN. We showed that the lymphoproliferation induced by alpha CD3 and concanavalin A was decreased in both lesioned groups, but phytohemagglutinin-induced mitogenesis was more impaired in the right than in the left lesioned animals. Hence, the time course effects of the right lesions of SN shifted from depression to enhancement of the T lymphocyte responsiveness. This shift appeared to occur around the two weeks period following the lesion. These immunomodulatory effects of unilateral SN lesioning, which depended on time and side of lesion, were similar to those observed after hemidecortication. Based on these findings, it is reasonable to suggest that asymmetry in brain immunomodulation involves functionally related dopaminergic and cortical networks.

Handedness is not related to self-reported disease incidence

A hand preference inventory and a disease questionnaire were administered to a sample of 743 undergraduate students. The incidence of left-handedness was not related to the report of any of the diseases surveyed. Among right-handers, preference scores were slightly lower (less right-handed) in those reporting drug allergies or migraine. These data provide no support for the argument that handedness and immune disorders are related.

Sex-dependent association between immune function and paw preference in two substrains of C3H mice

Asymmetry in brain modulation of the immune system has been previously described in mice. Paw preference is known to be associated with immune reactivity but the respective roles of sex and genetic background in this association remain to be elucidated. In this work, male and female mice of the C3H/He and C3H/OuJIco substrains were selected as right- and left-handers. Mitogen-induced lymphoproliferation and natural killer cell activity were then tested. Left-handed female mice of both C3H substrains exhibited higher mitogenesis than right-handers but no association between paw preference and NK cell activity was found in females. Conversely, in males of both substrains, right-handers showed enhanced NK cell activity compared to left-handers but no association between paw preference and mitogenesis was observed in males. Only small differences in the strength, but not in the direction, of the association between paw preference and immune functions were observed between the two C3H substrains. These results show that the association between paw preference and immune reactivity in mice varies according to the immune parameters tested and is a sex-dependent phenomenon in which the genetic background may be involved.

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.