HLA antigens in schizophrenia and mood disorders

Association of HLA-DR/DQ polymorphisms with schizophrenia in Tunisian patients

BACKGROUND AND OBJECTIVES

The hypothesis that human leukocyte antigens (HLAs) confer susceptibility to schizophrenic disorders has been tested by studying linkage and association in family samples. Our goal was to evaluate the role of HLA in the risk of developing schizophrenia in a Tunisian population.

DESIGN AND SETTINGS

Blood samples for this case-control study were collected from patients of the Department of Psychiatry at the Military Hospital of Tunisia between July 2012 and May 2013.

METHODS

A total of 140 patients with schizophrenia were recruited for genetic analysis. Controls included 100 persons matched for age, sex, and risk factors. Participants were tested for HLA class II alleles. HLA-DRB1 and HLA-DQB1 alleles were genotyped using polymerase chain reaction sequence-specific primers.

RESULTS

This study indicates that the alleles most responsible for disease susceptibility are DRB1*03 (P < 10-3) and DQB1*02 (P < 10-3) (P denotes probability values). The most protective alleles are DRB1*13 (P=.013) and DQB1*05 (P < 10-3). Further results revealed that DRB1*0301/DQB1*0201(P < 10-3), DRB1*0401/DQB1*0301 (P < 10-3) and DRB1*1101/DQB1*0301 (P < 10-3) are haplotypes most conducive to disease susceptibility.

CONCLUSION

The present findings support an association between schizophrenia and the HLA-DR-DQ locus among a Tunisian population. To our knowledge, this is the first study performed to analyze the association of HLA DRB1/DQB1 alleles on schizophrenia susceptibility in Tunisia.

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.

Reconsidering the association between the major histocompatibility complex and bipolar disorder

Bipolar disorder (BD) is a cyclical and chronic affective disorder, globally recognized as an important public health problem and characterized by mood changes with recurring phases such as mania and depression. It is considered a complex disease, depending on the interaction of genetic and environmental triggers (stressors factors), but with a poorly known pathogenesis. Recent studies have implicated immune factors in the pathogenesis of BD and more particularly associated with different human major histocompatibility complex (MHC) regions. A major consortium study have recently linked BD to hundreds of variations with stronger associations in the MHC region, such as the rs3130297 SNP, located in the NOTCH4 gene, with an additional overlapping association with schizophrenia. This short review focuses on studies that investigated the association between bipolar disorder and the MHC, and the involvement of the immune system in the pathogenesis of the disease, in order to provide further information for additional diagnostic and therapeutic strategies. Fully understanding the etiology and pathophysiology of BD is extremely important to define new approaches for intervention and prevention, maybe through the modulation of the immune system.

HLA-DRB1 association with schizophrenia in Saudi Arabian patients

OBJECTIVE

This study is aimed to examine the association between HLA-DRB1 alleles frequency and schizophrenia in Saudi Arabs.

METHODS

The DRB1 region of major histocompatibility complex was screened by polymerase chain reaction/sequence specific primers (PCR/SSP) in 180 schizophrenia patients and 200 matched controls.

RESULTS

The frequency of DRB1*03 was found to be significantly higher in schizophrenia patients as compared to controls, whereas a significantly lower frequency of DRB1*06 was observed in schizophrenia patients as compared to controls. Molecular sub-typing of the most prevalent allele DRB1*03 (30.56%) revealed the presence of DRB1*030101, *030102 alleles.

CONCLUSION

The results of this study suggested a positive association between DRB1*03 (DRB1*030101, DRB1*030102) with schizophrenia and a negative association of DRB1*06 with schizophrenia in Saudi Arabs. However it is not clear whether the DRB1*03 alleles have a direct causal role in the etiology of schizophrenia or if they are in direct linkage disequilibrium with another true susceptibility locus. Since schizophrenia is a complex phenotype, it is expected that many factors might act together to produce the final outcome. Further studies are warranted involving larger population to confirm the observations reported in this study.

Human leukocyte antigen DR1 in Japanese and Turkish patients with schizophrenia

The main focus of this review has been to discuss the probable causes of the higher frequency of HLA DR1 antigen in patients with schizophrenia from Japan and Turkey, and also to see whether there was an impact of belonging to the Ural-Altaic language group. A general medline search on the terms HLA and schizophrenia was used as the method to determine HLA studies in patients with schizophrenia. Most of the findings were inconsistent regarding the increased or decreased frequencies of different Class I and II antigens. However, there were interesting results, which have been consistently repeated in several Japanese studies and in a Turkish study. HLA DR1 antigen was statistically significantly increased in Japanese and Turkish patients with schizophrenia. As Japanese and Turkish languages belong to the Ural-Altaic language group, HLA DR1 antigen might have a specific association with schizophrenia in Japanese and Turkish patients. Searching the frequency of HLA DR1 antigen in patients with schizophrenia in other members of Ural-Altaic language group is necessary to support this hypothesis. Other language groups (e.g. Indo-European) should be assessed as well.

No association of TAP2 polymorphisms in Korean patients with schizophrenia

OBJECTIVES

Polymorphisms of transporters associated with antigen-processing (TAP) genes might influence the susceptibility to schizophrenia by altering the antigen-processing pathway. The aim of this study was to verify the relationship between schizophrenia and the polymorphisms of TAP2 genes.

METHOD

Two hundred and fifty-seven Korean patients diagnosed with schizophrenia according to DSM-IV and 184 normal controls participated in this study. TAP2 polymorphic residues at positions 379, 565 and 665 were typed using amplification refractory mutation system-polymerase chain reaction single-strand conformation polymorphism.

RESULTS

Distribution of the alleles and genotypes in patients with schizophrenia was not significantly different from those of controls.

CONCLUSIONS

This study did not show the association of the TAP2 gene with schizophrenia in the Korean population.

Familial bipolar disorder and multiple sclerosis: a three-generation HLA family study

The coexistence of bipolar disorder (BD) and multiple sclerosis (MS) is well known. Manic symptoms may represent initial symptoms of MS, at least in some cases, and follow the MS-HLA phenotype frequencies. The purpose of this study was to examine the possible relation of BD and MS based on an HLA family study of a woman with BD and comorbid MS, with family history of BD. Five members of the family from three generations (the patient, her mother, her brother, and her two daughters) were examined regarding the two disorders and the HLA class I and II specificities, performed by serology and molecular techniques. Her deceased father, her brother, and her older daughter suffered from BD. Moreover, in her brother, BD and MS comorbidity was diagnosed. The three affected members and the nonaffected grandmother share the same class I and II, HLA-A2, B18, CW8, DR2, DQ1 haplotype. The shared class II, HLA-DR2, DQ1 haplotype among affected individuals, which is well known to be associated with MS in Caucasians, suggests a possible susceptibility locus for BD, mapped on chromosome 6, very close to the HLA region, underlying the clinical comorbidity of the two disorders.

Polymorphism of CTLA-4 gene at position 49 of exon 1 may be associated with schizophrenia in the Korean population

This study was carried out to investigate the association of a polymorphism of the CTLA-4 gene, at position 49 of exon 1, with schizophrenia in the Korean population. Among Korean patients diagnosed with schizophrenia according to DSM-IV, 116 patients who met the selection criteria were recruited for the study. One hundred and forty-nine normal healthy Koreans from the Catholic Hemopoietic Stem Cell Information Bank, were used as a normal control group. DNA was extracted from whole blood using proteinase K and the CTLA-4 gene region was amplified by polymerase chain reaction. Geneo typing was performed by single strand conformation polymorphism (SSCP). The genotype and allele distribution in patients with schizophrenia was significantly different from that seen in the control group. This study suggests a putative role of the CTLA-4 gene polymorphism at position 49 of exon 1 for schizophrenia in the Korean population, although the detailed mechanisms remained to be elucidated.

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.

Human leukocyte antigen (HLA) DRB1 alleles in Kuwaiti Arabs with schizophrenia

The frequency of human leukocyte anti- gen DRB1 alleles was determined in a cohort of 194 Kuwaiti Arabs consisting of 80 schizophrenia patients and 114 ethnically matched healthy controls, using a polymerase chain reaction-sequence specific primers method. A total of 12 DRB1 alleles were identified in this Kuwaiti cohort. A statistically significant difference was detected in the frequency of alleles DRB1(*)04 and DRB1(*)13 between the schizophrenia patients and controls. Allele frequency of DRB1(*)04 in schizophrenia patients was 14% compared with nearly 7% in controls (P = 0.028). For DRB1(*)13, the allele frequency was found to be 18% in schizophrenia patients compared with 9% in the controls (P = 0.015). For alleles, DRB1(*)03, DRB1(*)07, and DRB1(*)16 the frequency was higher in controls compared with schizophrenia patients. The frequency of DRB1(*)01, DRB1(*)08, DRB1(*)10, DRB1(*)11, and DRB1(*)15 alleles was almost identical in schizophrenia patients and controls. For the remaining alleles, the differences between the two groups were not statistically significant. Am. J. Med. Genet. (Neuropsychiatr. Genet.) 96:870-872, 2000.

Support for an association between HLA-DR1 and schizophrenia in the Japanese population

An increase of HLA-DR1 has been observed in schizophrenia patients from the Japanese population. A decrease of DR4, which was reported in Caucasian patients, has also been found in some of the Japanese studies. This small study further investigated frequencies of HLA-DR1 and DR4 in unrelated Japanese patients with schizophrenia (n = 45) and healthy comparison subjects (n = 117). The number of patients possessing DR1 was higher (10 of 45, 22%) compared with the comparison group (11 of 117, 9.4%, P = 0.03). This may support the previous observation of an increased DR1 frequency in the Japanese patients. When the present data is combined with three previous studies, proportions of the Japanese subjects with DR1 were 98 of 588 schizophrenia patients (16.7%) vs. 93 of 942 comparison subjects (9.9%). However, no difference was observed in DR4 frequencies between the patients (51%) and comparison subjects (44%). Am. J. Med. Genet. (Neuropsychiatr. Genet.) 96:725-727, 2000.

Schizophrenia and the HLA-DRB1 gene in the Japanese population

OBJECTIVE

Small Japanese studies have suggested that patients with schizophrenia have higher rates of the HLA-DR1 gene than normal subjects. The authors' goal in the present study was to confirm this finding in a larger number of Japanese subjects. They also investigated the rate of DR4 in Japanese patients with schizophrenia because it has been reported that Caucasian patients with schizophrenia have higher rates of DR4.

METHOD

They studied the occurrence of the HLA-DRB1 gene in 233 unrelated Japanese patients with schizophrenia compared with the occurrence of the gene in a group of 493 healthy Japanese volunteers.

RESULTS

A larger proportion of the patients with schizophrenia (15.9%) than the comparison subjects (10.5%) were found to have DR1 (DRB1*0101). The proportion of patients (36.9%) and comparison subjects (40.6%) with DR4 did not differ significantly.

CONCLUSIONS

Consistent with the findings of three other Japanese studies, the findings of the present study suggest that the rate of HLA-DR1 may be higher in Japanese patients with schizophrenia than in normal Japanese subjects. No evidence for an association between schizophrenia and the rate of DR4 was obtained in this study, although the combined data from the present study and other Japanese studies support the finding of lower rates of DR4 among patients with schizophrenia.