HLA antigens in schizophrenia, major depressive disorder, and schizoaffective disorder

Variation in the major histocompatibility complex [MHC] gene family in schizophrenia: associations and functional implications

Schizophrenia is a chronic debilitating neuropsychiatric disorder with a complex genetic contribution. Although multiple genetic, immunological and environmental factors are known to contribute to schizophrenia susceptibility, the underlying neurobiological mechanism(s) is yet to be established. The immune system dysfunction theory of schizophrenia is experiencing a period of renewal due to a growth in evidence implicating components of the immune system in brain function and human behavior. Current evidence indicates that certain immune molecules such as Major Histocompatibility Complex (MHC) and cytokines, the key regulators of immunity and inflammation are directly involved in the neurobiological processes related to neurodevelopment, neuronal plasticity, learning, memory and behavior. However, the strongest support in favor of the immune hypothesis has recently emerged from on-going genome wide association studies advocating MHC region variants as major determinants of one's risk for developing schizophrenia. Further identification of the interacting partners and receptors of MHC molecules in the brain and their role in down-stream signaling pathways of neurotransmission have implicated these molecules as potential schizophrenia risk factors. More recently, combined brain imaging and genetic studies have revealed a relationship between genetic variations within the MHC region and neuromorphometric changes during schizophrenia. Furthermore, MHC molecules play a significant role in the immune-infective and neurodevelopmental pathogenetic pathways, currently hypothesized to contribute to the pathophysiology of schizophrenia. Herein, we review the immunological, genetic and expression studies assessing the role of the MHC in conferring risk for developing schizophrenia, we summarize and discuss the possible mechanisms involved, making note of the challenges to, and future directions of, immunogenetic research in schizophrenia.

Immunomodulation in schizophrenia: A study among the Indian schizophrenia patients of Siliguri, West Bengal

Authors investigated the circumstantial evidence for autoimmunity in schizophrenia patients of Siliguri by considering the immune parameters like HLA Class I genes, IL-2 and IL6 and T cell subsets. Low resolution PCR-SSP method was applied for typing the HLA genes. Serum levels of IL-2 and IL-6 were measured by ELISA method. The CD4+ and CD8+ subset count were done using flow cytometry. A significant increase in HLA A*03 gene was observed in patients along with the significant decrease of HLA-A*31 and HLA-B*51. Both IL-2 and IL-6 were found to have decreased levels in the patients. Although the mean percentage of CD4+ and CD8+ cells was higher in patients but not significantly higher than controls. These cumulative preliminary findings are suggestive of alterations in the immune system of schizophrenia patients of this region.

Study of HLA Class I gene in Indian schizophrenic patients of Siliguri, West Bengal

The authors studied the prevalence of the human leukocyte antigen (HLA) Class I gene in 136 (85 male, 51 female) India-born schizophrenia patients residing in and around the Siliguri subdivision of West Bengal by the PCR-SSP method. The control group consisted of 150 age- and sex-matched healthy individuals from the same ethnic group as the patients. Increased frequency of HLA A*03 as well as decreased frequencies of HLA A*31 and HLA B*51, was noted. The study suggests the possible existence of a susceptibility locus for schizophrenia within the HLA region.

The role of HLA-G in cytokine homeostasis during early pregnancy complicated with maternal infections: a novel etiopathological approach to the neurodevelopmental understanding of schizophrenia

Schizophrenia is perhaps the most enigmatic and tragic psychotic disorder with remarkable mortality and morbidity. Schizophrenia is complex and clinically a heterogeneous disorder. The etiological basis of schizophrenia ranges from autoimmune to neurodevelopmental hypothesis in one hand and involvement of different major gene segment with susceptibility loci on the other. Recently, neurodevelopmental hypothesis gained much impetus over the other domain. To support the neurodevelopmental basis, a number of investigations have shown that maternal infections during pregnancy increases the risk of the offspring developing schizophrenia and other neurodevelopmental disorders. The pathological mechanisms underlying this phenomenon is largely unknown. Many have suggested the involvement of different immune markers and shown that cytokines generated in response to maternal infection alter early brain development through their inflammatory activity. However, these findings have escaped discussion on various important issues related to cytokine homeostasis which depends on a large number of immune parameters including non-classical HLA-G molecules. Infections during early stages of pregnancy may alter cytokine regulation by disturbing the whole uterine immune milieu. To elucidate this issue, authors have tried to correlate the possible relationships between maternal infections and aberration of immune networking at the feto-maternal interface and their subsequent influence on the structural and functional abnormalities of the developing brain. The authors hypothesize that there exists a counter regulatory interaction among proinflammatory cytokines like TNF-alpha, HLA-G molecules and different immune cells like NK cells. We emphasize that HLA-G molecules are the novel immune players which maintain the immune homeostasis during early pregnancy in a manner that it can protect developing fetus from maternal immune attack. However, maternal infections may lead to the disturbance of HLA-G expression which in turn may fail to maintain its otherwise inhibitory potential to down regulate the detrimental inflammatory cytokines. Investigation on such interaction may unravel novel molecular mechanisms of neurodevelopmental basis of schizophrenia. Testing of our proposed hypothesis on animal models and on in vitro derived extravillous trophoblast cell lines holds promise of great insights to usher a new dimension of schizophrenia research and for developing new therapeutic strategies for better treatment and to adopt genetic prediction in schizophrenia management paradigm.

Relationship between class I and II HLA antigens in schizophrenia and eye movement disturbances: a preliminary study

The region coding human leukocyte antigen (HLA) on chromosome 6q21 was shown to be associated with both the vulnerability to schizophrenia and presence of eye movement disturbances (EMD). The aim of this preliminary study was to investigate how individual class I and II HLA antigens in schizophrenic patients may be related to schizophrenia and to the intensity of two kinds of EMD: fixation and smooth pursuit. The incidence of HLA antigens was compared between 40 schizophrenic patients (17 male, 23 female) and 198 healthy control subjects (112 male, 86 female). In schizophrenic patients, the intensity of EMD assessed by infrared reflectometry and quantified on a scale from 0 to 3 was correlated with the incidence of HLA antigens. A number of differences regarding HLA antigens were found between schizophrenic patients and healthy subjects. Significant correlation was also obtained between some EMD and a number of HLA antigens. Antigens A24 and A28 were found to occur in different frequencies in schizophrenic patients and healthy control subjects. They also correlated with EMD on the fixation and smooth pursuit tests. The results obtained show an association between HLA antigens and EMD as an endophenotypic marker of schizophrenia, and may add to other findings on susceptibility loci for schizophrenia on chromosome 6p21. A limitation of this study is a small number of investigated patients with schizophrenia.

TNFB polymorphism may be associated with schizophrenia in the Korean population

This study was conducted to test the association between the tumor necrosis factor (TNF)-beta gene (B) polymorphism and schizophrenia in the Korean population. 127 patients with schizophrenia according to the DSM-IV criteria and 202 healthy controls were enrolled in this study. Patients and controls were biologically unrelated age and sex-matched native Koreans. Genotyping for the TNFB polymorphism was performed by polymerase chain reaction-restriction fragment length polymorphism. Genotype and allele distributions of the TNFB polymorphism in patients with schizophrenia were significantly different from those of the controls. Subjects with the TNFB*2 allele had an increased risk for schizophrenia (Odds Ratio=1.76, 95% CI=1.27-2.45). The present study suggests that the TNFB polymorphism may confer susceptibility to schizophrenia in the Korean population.

HLA class I distribution in Japanese patients with schizophrenia

Several Caucasian studies and one Japanese study have observed associations between human leukocyte antigen (HLA) class I specificities, including A24 (9) and A26 (10) and schizophrenia. Most of those studies were conducted in 1970s and early 1980s, when the typing technique of HLA was not adequately reliable. Also, an operational diagnostic system was not employed in many of the studies. The present study investigated frequencies of HLA-A specificities in schizophrenia patients (ICD-10 and DSM-III-R, n=98) and sex-matched healthy controls (n=392) from population in the southwestern part of Japan. HLA-B and -C specificities were studied in addition. Frequencies of subjects possessing A24 and A26 were not different between the patients and controls (54% and 24% in the patients and 62% and 24% in the controls, respectively). No significant difference was found in frequencies of other class I (A, B, and C) specificities between the patients and the controls. Thus, the present study provided no evidence for an association between the HLA class I specificities, including A24, A26, and others, and schizophrenia in the Japanese population.

Schizophrenia and HLA: a review

A number of reports of genetic association of human leucocyte antigens (HLA) and alleles with schizophrenia have recently been published. A schizophrenia locus on chromosome 6p near the HLA region has also been reported, on the basis of linkage studies. We have therefore reviewed the investigations of association of HLA with schizophrenia published from 1974 to date, and have also briefly reviewed the chromosome 6p linkage studies. Two or more groups of investigators have reported association of each of the following HLA antigens or alleles with schizophrenia - A9 or its A24 subspecificity, A28, A10, DRB1*01 and DRw6. However, these results may represent Type I errors caused by small sample size, inappropriate diagnostic, laboratory and/or statistical methodology, and/or incorrectly chosen comparison subjects. Hypothesis-driven negative associations of DRB1*04 and DQB1*0602 with schizophrenia have also been reported. Taken together, however, HLA association investigations provide only weak evidence for the existence of either resistance or susceptibility loci for schizophrenia close to the HLA region at the 6p21.3 band and, indeed, recently reported investigations that controlled for most of these confounders found no evidence of association. Linkage studies suggest that a susceptibility locus may exist and that it may be within the HLA region, but again the evidence is far from conclusive. Further HLA association investigations should employ operational diagnostic criteria, comparison subjects screened for illness and HLA genotyping, and should include both association studies of candidate alleles and transmission disequilibrium and haplotype relative risk studies.

HLA antigens in childhood onset schizophrenia

Evidence of immune system abnormalities in adult schizophrenia has prompted examination of the human leukocyte antigen (HLA) system. Childhood onset schizophrenia offers a unique opportunity to test neurodevelopmental hypotheses of schizophrenia, including those which implicate components of the immune system. In the present study, class I and II HLA antigens were typed using sequence-specific primers and the polymerase chain reaction in 28 childhood onset schizophrenics and 51 ethnically matched healthy subjects. Groups were compared for frequencies of HLA antigens reported to be associated with schizophrenia and/or autoimmune disorders. We hypothesized that antigen frequencies would differ between schizophrenic and healthy children, suggesting that some dimension of the neurodevelopmental disturbance experienced by these children may be mediated by subtle abnormalities of immune function. There were no significant differences between schizophrenic and healthy subjects in the frequency of any antigen tested. These findings do not support HLA-associated pathology in childhood onset schizophrenia.

A negative association of schizophrenia with an allele of the HLA DQB1 gene among African-Americans

Using polymorphisms of the human leukocyte antigen (HLA) DQB1 gene, a case-control study was conducted in a group of patients with schizophrenia (DSM-III, n = 58) and psychiatrically normal controls matched for ethnicity (n = 72), living in the same geographical area. A significant negative association of allele HLA DQB1*0602 with schizophrenia was present among African-Americans (odds ratio 0.19), but could not be detected in Caucasians.

HLA antigens and neuroleptic response in clinical subtypes of schizophrenia

The frequency of HLA antigens of A and B loci was examined in a carefully selected sample of 91 schizophrenic patients from central Italy. This population showed no increase in antigens compared with the control group. However, in agreement with previous studies, a slight increase in A1 was observed in the hebephrenic subgroup and, in a lesser extent, an increase of A2 was found in the paranoid subgroup. Although these increases are more prominent when the subgroups are compared and tend to support the case for genetic heterogeneity, they fail to reach statistical significance. Response to neuroleptic treatment was studied in an attempt to further subdivide the clinical subgroups. A1-negative and A2-positive paranoid patients demonstrated a statistical better response to neuroleptics. The findings suggest that schizophrenia should be considered a heterogenous disease and that response to neuroleptics can be employed as an instrument of biological subclassification.

Relationship of HLA to schizophrenia in 10 nuclear families

We tested the hypothesis of linkage of HLA (human leukocyte antigens) and schizophrenia in 10 nuclear families that were ascertained on the basis of at least two siblings affected with chronic schizophrenia (SCH), as defined by Research Diagnostic Criteria, with or without superimposed affective disorder. All available parents and siblings were interviewed and typed for HLA antigens at the A, B, C, and Dr loci. Lod scores for linkage between HLA and a putative SCH-locus were calculated using the program LIPED, assuming several possible models for the mode of transmission of the SCH locus. Linkage was also tested with DSM-III schizotypal and paranoid personality disorders considered as part of the illness phenotype. The lod score analysis indicated that for most models of inheritance of schizophrenia, close linkage to HLA could be excluded. The results did not change if individuals with "spectrum" disorders were considered affected. We also tested for linkage using the affected sib-pair method which does not require any assumptions about the mode of transmission of the illness. The results of this analysis also indicated that linkage to HLA was very unlikely. If our results are considered together with other published studies, a susceptibility locus for schizophrenia or "schizophrenia spectrum" is not likely to be in the HLA region of chromosome 6.

Biological substrates of schizophrenia

Schizophrenia is increasingly believed to represent a group of organic disorders which primarily, although not exclusively, affect the central nervous system. Our purpose is to review a representative sample of twentieth-century literature which speaks to the biological substrates of the syndrome. Subjects reviewed include genetic and environmental contributions to the onset of illness, early and recent findings of gross structural anomalies, and apparent histopathological alterations in cerebral cortex, cerebellar vermis, limbic system, and brain stem, as well as problems of cerebral asymmetry. Data from a diverse group of electrophysiological studies reveal several promising correlates of these areas of investigation. Despite the inconsistent nature of the findings to date, several themes have begun to emerge, including patterns of hypofrontal/hyperparietal regional cerebral flow and glucose utilization, left hemispheric dysfunction, and deficits of interhemispheric information processing. The interpretation and significance of these emerging patterns remains unclear and must await more profound insights into the nature of normal and abnormal cerebral function.

Genetic markers in alcoholism: no association with HLA

We carried out a study on 63 patients suffering from alcoholism in order to determine the frequency of 27 HLA antigens. In comparison to healthy blood donors no significant deviation of HLA distributions in alcoholics was found. The data on alcoholic patients with physical consequences such as cerebral seizures, liver cirrhosis and polyneuropathy failed to identify an association with HLA.