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

Association of HLA-A, -B, -C, -DRB1 and -DQB1 alleles at amino acid level in individuals with schizophrenia: A study from South India

BACKGROUND

Schizophrenia, a chronic severe psychiatric illness of unknown aetiology, has been shown to be associated with HLA alleles but at varied degree in different population. The present study has focussed on analysing the frequency of HLA class I and class II alleles in persons with schizophrenia from South India.

METHODS

Ninety seven individuals with schizophrenia and 103 age- and gender-matched controls were typed for HLA- A, B, C, DRB1 and DQB1 loci by next-generation sequencing in Illumina MiniSeq using MIA FORA NGS FLEX HLA typing kit.

RESULTS

The results showed that HLA-A*01:01:01, B*37:01:01 and C*01:02:01 were positively associated with schizophrenia while HLA-B*35:03:01 and DRB1*04:03:01 were negatively associated. Gender-specific associations revealed that DRB1*10:01:01 and DQB1*05:01:01 were positively associated while DQB1*03:02:01 was negatively associated with female subjects with schizophrenia. A*24:02:01~B*37:01:01~C*06:02:01~DRB1*10:01:01~DQB1*05:01:01 is the predominant haplotype in schizophrenia population when compared to healthy controls. Amino acid association in susceptible and protective alleles has shown that the presence of peptide in the peptide-binding groves of mature HLA-A protein (K, M, V, R and V at 44th, 67th, 150th, 156th and 158th position), HLA-B protein (D and S at 77th and 99th position) and HLA-C protein (M at 99th position) confer susceptibility to the disease, only in the absence of E (Glutamic acid) at 74th position in mature HLA-DRB1 protein. Interaction of amino acids in protective alleles namely B*35:01:01 and DRB1*04:03:01 has revealed that aspartic acid at 114th (D) position in mature HLA-B protein and glutamic acid (E) at 74th position of mature HLA-DRB1 protein have a combined effect in protecting against the disease.

CONCLUSION

The study has revealed the HLA association with schizophrenia in south Indian population. The amino acid interaction with the disease needs to be confirmed in a larger population.

Immunity and mental illness: findings from a Danish population-based immunogenetic study of seven psychiatric and neurodevelopmental disorders

Human leukocyte antigen (HLA) genes encode proteins with important roles in the regulation of the immune system. Many studies have also implicated HLA genes in psychiatric and neurodevelopmental disorders. However, these studies usually focus on one disorder and/or on one HLA candidate gene, often with small samples. Here, we access a large dataset of 65,534 genotyped individuals consisting of controls (N = 19,645) and cases having one or more of autism spectrum disorder (N = 12,331), attention deficit hyperactivity disorder (N = 14,397), schizophrenia (N = 2401), bipolar disorder (N = 1391), depression (N = 18,511), anorexia (N = 2551) or intellectual disability (N = 3175). We imputed participants' HLA alleles to investigate the involvement of HLA genes in these disorders using regression models. We found a pronounced protective effect of DPB1*1501 on susceptibility to autism (p = 0.0094, OR = 0.72) and intellectual disability (p = 0.00099, OR = 0.41), with an increased protective effect on a comorbid diagnosis of both disorders (p = 0.003, OR = 0.29). We also identified a risk allele for intellectual disability, B*5701 (p = 0.00016, OR = 1.33). Associations with both alleles survived FDR correction and a permutation procedure. We did not find significant evidence for replication of previously-reported associations for autism or schizophrenia. Our results support an implication of HLA genes in autism and intellectual disability, which requires replication by other studies. Our study also highlights the importance of large sample sizes in HLA association studies.

HLA-A*11:01 is associated with levetiracetam-induced psychiatric adverse events

Levetiracetam (LEV) is effective for focal and generalized epilepsy and is used worldwide because of its relatively few drug interactions and favorable tolerability. However, some psychiatric adverse events (PAEs) have been reported, resulting in drug withdrawal. The pathophysiology of LEV-induced PAE has not yet been elucidated. In this study, we investigated the relationship between PAEs and human leukocyte antigen (HLA) genes. Eleven epilepsy patients, who developed PAEs after the administration of LEV and spontaneously improved after drug withdrawal, were enrolled retrospectively. Genomic DNA from the peripheral blood was extracted, and four-digit allele genotyping of HLA genes was performed. The genotype frequencies of HLA genes were compared to those of 80 patients in which LEV was well tolerated, as well as to 485 individuals from the general Korean population. The frequency of the HLA-A*1101 allele was significantly higher in the LEV-induced PAEs group compared to both the LEV-tolerant group (p = 0.021, OR 4.80, 95% CI 1.30-17.74) and the general Korean population (p = 0.015, OR 4.62, 95% CI 1.38-15.45). This study is the first attempt at investigating the relationship between the HLA system and LEV-induced PAE. The results of this study suggest that the HLA-A*1101 allele could be a risk factor for the development of PAEs.

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.

HLA associations in schizophrenia: are we re-discovering the wheel?

Associations between human leukocyte antigen (HLA) polymorphisms on chromosome 6p and schizophrenia (SZ) risk have been evaluated for over five decades. Numerous case-control studies from the candidate gene era analyzed moderately sized samples and reported nominally significant associations with several loci in the HLA region (sample sizes, n = 100-400). The risk conferred by individual alleles was modest (odds ratios < 2.0). The basis for the associations could not be determined, though connections with known immune and auto-immune abnormalities in SZ were postulated. Interest in the HLA associations has re-emerged following several recent genome-wide association studies (GWAS); which utilized 10- to 100-fold larger samples and also identified associations on the short arm of chromosome 6. Unlike the earlier candidate gene studies, the associations are statistically significant following correction for multiple comparisons. Like the earlier studies; they have modest effect sizes, raising questions about their utility in risk prediction or pathogenesis research. In this review, we summarize the GWAS and reflect on possible bases for the associations. Suggestions for future research are discussed. We favor, in particular; efforts to evaluate local population sub-structure as well as further evaluation of immune-related variables in future studies.

Evaluation of HLA polymorphisms in relation to schizophrenia risk and infectious exposure

BACKGROUND

Genome-wide association studies (GWAS) implicate single nucleotide polymorphisms (SNPs) on chromosome 6p21.3-22.1, the human leukocyte antigen (HLA) region, as common risk factors for schizophrenia (SZ). Other studies implicate viral and protozoan exposure. Our study tests chromosome 6p SNPs for effects on SZ risk with and without exposure.

METHOD

GWAS-significant SNPs and ancestry-informative marker SNPs were analyzed among African American patients with SZ (n = 604) and controls (n = 404). Exposure to herpes simplex virus, type 1 (HSV-1), cytomegalovirus (CMV), and Toxoplasma gondii (TOX) was assayed using specific antibody assays.

RESULTS

Five SNPs were nominally associated with SZ, adjusted for population admixture (P < .05, uncorrected for multiple comparisons). These SNPs were next analyzed in relation to infectious exposure. Multivariate analysis indicated significant association between rs3130297 genotype and HSV-1 exposure; the associated allele was different from the SZ risk allele.

CONCLUSIONS

We propose a model for the genesis of SZ incorporating genomic variation in the HLA region and neurotropic viral exposure for testing in additional, independent African American samples.

Genetic correlates of medical comorbidity associated with schizophrenia and treatment with antipsychotics

PURPOSE OF REVIEW

High comorbidity rates for various medical conditions have been documented in schizophrenia, being explained by factors either inherent to the disease or associated with antipsychotic treatment. The aim of this study is to review the genetic factors contributing to medical comorbidity in schizophrenia.

RECENT FINDINGS

Based on clinical genetic studies in schizophrenia, comorbid impaired glucose tolerance/type 2 diabetes mellitus, most autoimmune disorders and cardiac autonomic dysregulation have the strongest evidence for familial predisposition. Similarly, of antipsychotic-induced adverse drug reactions, tardive dyskinesia, neuroleptic malignant syndrome, and antipsychotic-induced weight gain have some evidence for familial clustering. On the molecular genetic level, schizophrenia seems to share specific genes with type 2 diabetes mellitus and with autoimmune disorders. Various genes have been proposed to account for the reduced incidence of rheumatoid arthritis and cancer in schizophrenic patients and their relatives. Many pharmacogenetic association studies have pinpointed numerous, though often contradictory or poorly replicated, genes of modest effect size for tardive dyskinesia, neuroleptic malignant syndrome, clozapine-induced agranulocytosis, hyperprolactinaemia, antipsychotic-induced weight gain, and antipsychotic-induced QT prolongation.

SUMMARY

Unravelling the genetic underpinnings of medical comorbidity associated with schizophrenia and its treatment is expected to highlight new pathogenetic pathways in both schizophrenia and comorbid medical conditions, and introduce personalized treatment strategies for schizophrenia patients.

Similarities and differences in peripheral blood gene-expression signatures of individuals with schizophrenia and their first-degree biological relatives

Several studies have evaluated the potential utility of blood-based whole-transcriptome signatures as a source of biomarkers for schizophrenia. This endeavor has been complicated by the fact that individuals with schizophrenia typically differ from appropriate comparison subjects on more than just the presence of the disorder; for example, individuals with schizophrenia typically receive antipsychotic medications, and have been dealing with the sequelae of this chronic illness for years. The inability to control such factors introduces a considerable degree of uncertainty in the results to date. To overcome this, we performed a blood-based gene-expression profiling study of schizophrenia patients (n = 9) as well as their unmedicated, nonpsychotic, biological siblings (n = 9) and unaffected comparison subjects (n = 12). The unaffected biological siblings, who may harbor some of the genetic predisposition to schizophrenia, exhibited a host of gene-expression differences from unaffected comparison subjects, many of which were shared by their schizophrenic siblings, perhaps indicative of underlying risk factors for the disorder. Several genes that were dysregulated in both individuals with schizophrenia and their siblings related to nucleosome and histone structure and function, suggesting a potential epigenetic mechanism underlying the risk state for the disorder. Nonpsychotic siblings also displayed some differences from comparison subjects that were not found in their affected siblings, suggesting that the dysregulation of some genes in peripheral blood may be indicative of underlying protective factors. This study, while exploratory, illustrated the potential utility and increased informativeness of including unaffected first-degree relatives in research in pursuit of peripheral biomarkers for schizophrenia.

Analysis of the role of human leukocyte antigen class-I genes to understand the etiopathology of schizophrenia

BACKGROUND

Schizophrenia is the paradigmatic illness of psychiatry. The involvement of immunological and immunopathological mechanisms in the etiopathogenesis of schizophrenia has been a matter of research, with recently increasing effort.

AIMS

In this study, we investigated the incidence of human leukocyte antigen (HLA) Class I antigens to understand the role of HLA genes in schizophrenia.

MATERIALS AND METHODS

India born schizophrenic patients in and around Siliguri who attended outpatient department (OPD) of Department of Psychiatry, North Bengal Medical College and Hospital were considered for the present study. After the longitudinal follow up, 50 patients were enrolled for the study. The same number of age, sex and ethnically matched healthy subjects were considered as control. Low resolution polymerase chain reaction-sequence specific primer method was applied for typing the HLA antigens.

STATISTICS

The phenotype frequencies were calculated by direct count. chi(2) test was done to compare the frequency of each antigen among the patients and control group and it was followed by Fisher's exact test. Relative risk was estimated by using Haldane's method.

RESULTS

The result showed that some of the HLA antigens are associated with the schizophrenia and significant increase were observed for HLA A*03 antigen along with the significant decrease for HLA A*25, A*31 and HLA B*51.

CONCLUSIONS

The study provides the evidence for the possible existence of susceptibility locus for schizophrenia within the HLA region. This preliminary observation may help to understand the etiological basis of this disorder and the study may further strengthen the HLA antigens as the marker for schizophrenia.

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.

Gene, gut and schizophrenia: the meeting point for the gene-environment interaction in developing schizophrenia

Both schizophrenia and celiac disease involve a genetic component. Several lines of evidence have shown a genetic relationship between these two conditions. Celiac disease is characterized by damage to the microscopic finger-like projections called villi, which line the small intestine and play a significant role in digestion, due to an inflammatory condition caused by a reaction to wheat gluten or related rye and barley proteins. Celiac disease represents not only malabsorption leading to a poor nutritional condition but also an alteration of gut permeability. Individuals with a history of a childhood celiac condition have a raised risk of developing schizophrenia. Psychotic symptoms often occur in adult celiac disease. It can be hypothesized that apart from malnutrition, the meeting point for the gene-environment interaction may be an alteration in gut permeability, in which the gut may lose its capacity to block exogenous psychosis-causing substances that may enter the body thus causing the development of schizophrenia and other mental conditions. To support this hypothesis, the conditional test was conducted to look at the combined effect of the CLDN5 gene involved in forming permeability barriers and the DQB1 gene that has been found to be associated with celiac disease. The results demonstrate that these two genes possibly work together in conferring a susceptibility to schizophrenia.

Is Schizophrenia Associated with Narcolepsy?

OBJECTIVE

To determine the nature of the relationship between schizophrenia-like psychosis and narcolepsy.

BACKGROUND

A relationship between schizophrenia and narcolepsy has long been postulated due to the association of schizophrenia-like psychosis with narcolepsy and its treatment.

METHOD

We report two patients who presented with schizophrenia-like psychosis of narcolepsy and review the literature regarding possible shared neurobiology between the two disorders that might explain their co-occurrence.

RESULTS

There appears to be little in the way of common pathology between these two conditions when symptoms, human leukocyte antigen associations, rapid eye movement sleep architecture, D2-dopamine receptor changes, and hypocretinergic function are examined.

CONCLUSIONS

The available literature suggests that schizophrenia-like psychosis in narcolepsy is most commonly medication related or a chance co-occurrence, with limited evidence for a separate psychosis of narcolepsy.

Tumor necrosis factor promoter haplotype associated with schizophrenia reveals a linked locus on 1q44

Using restriction fragment length polymorphism and pyrosequencing methods, we genotyped two TNFA gene promoter SNPs (-G308A, -G238A) and analyzed the haplotype structure in 24 Canadian families of primarily Celtic origin. Our results demonstrate that after correction for multiple testing based on simulations of 10 000 replicates of unlinked/unassociated data, there is evidence for association (P=0.026) of a specific haplotype (-308A, -238G) with schizophrenia and schizophrenia spectrum disorders with a family-based trimmed haplotype linkage disequilibrium test (Trimhap). Stratifying the 22 families with genome scan data by TNFA promoter haplotypes followed by reanalysis of linkage to schizophrenia throughout the genome, we identified few loci that exhibit a considerable increase in LOD/HLOD scores. A locus on chromosome 1q44 (D1S1609) demonstrated a significant increase (P=0.025) in LOD score from 0.15 to 3.01 with a broad definition of the schizophrenia phenotype and a dominant mode of inheritance. This result replicates a previously reported positive result of linkage of schizophrenia spectrum disorders to this area of the genome. We also illustrated that simulation studies are pivotal in evaluating the significance of results obtained with newer statistical methods, when multiple, but not independent, tests are performed, and when sample stratification is utilized to reduce the impact of heterogeneity or assess the interaction between loci.

Human leukocyte antigen-DQB1 alleles are not associated with schizophrenia in Kuwaiti Arabs

Schizophrenia is among the most severe and debilitating of psychiatric disorders and has a complex mode of inheritance. A susceptibility locus has been identified on chromosome 6 and some association studies involving human leukocyte antigen (HLA) genes have reported diverse results. The objective of the present study was to determine if there is an association between HLA-DQB1 alleles and schizophrenia in Kuwaiti Arabs. The frequency of HLA-DQB1 alleles was determined in a cohort of 195 Kuwaiti Arabs consisting of 81 schizophrenia patients and 114 ethnically matched healthy controls, using a polymerase chain reaction-sequence specific primers method. A total of nine DQB1 alleles were identified in this Kuwaiti cohort. The most prevalent DQB1 alleles in Kuwaiti schizophrenia patients were *0601 (28%), *0201 (23%) and *0501 (16%), respectively. However, no significant difference in the allele frequency was detected between schizophrenia patients and the controls. The DQB1*0602 allele, which has been negatively associated in African-Americans in previous reports, was not detected in the present Kuwaiti schizophrenia patients or controls.

Schizophrenia and other mental disorders require long-term adoptive immunotherapy

Many different microbial factors seem to contribute to the pathogenesis of schizophrenic and other psychiatric disorders. Activation of all T lymphocytes reactivates those downregulated by low-grade chronic infections and restores equilibrium in immune cell subpopulations. Different immune cell subpopulations express different neurotrophin receptors and produce different cytokines, particularly brain-derived neurotrophin (BDNF) and neurotrophin 3 (NT3) [M. Besser, R. Wank, J. Immunol. 162 (1998) 6303-6306] that appear to play a key role in schizophrenic and bipolar disorders [E. Jonsson, S. Brene, X.R. Zhang, et al., Acta Psychiatr. Scand. 95 (1997) 414-419; R.S. Duman, Arch. Gen. Psychiatry 54 (1997) 597-606; J.A. Siuciak, D.R. Lewis, S.J. Wiegand, R.M. Lindsay, Pharmacol. Biochem. Be 56 (1997) 131-137]. The hypothesis that adoptive immunotherapy is effective in psychiatric disorders will be supported by three case reports, in a patient with bipolar disorder, a patient with schizophrenia, and a patient with autism.

Investigation of linkage and association/linkage disequilibrium of HLA A-, DQA1-, DQB1-, and DRB1-alleles in 69 sib-pair- and 89 trio-families with schizophrenia

The hypothesis that HLA antigens confer susceptibility to schizophrenic disorders has been tested by studying linkage and association in a family sample with 69 sib-pair families. Suggestive evidence for linkage was obtained by nonparametric multipoint LOD score analysis with a maximum around DQB CAR (P = 0.0004), a microsatellite marker that is in linkage disequilibrium with the HLA antigen DQB1. Spurious evidence for negative association as calculated by the transmission disequilibrium test was found for HLA- DRB1*11 (chi-square = 11.72, corrected P value = 0.03) and for the haplotype DQB1*301-DQA1*501-DRB1*11 (chi-square = 11.3, corrected P value = 0.043). No evidence of association with these alleles was obtained in a sample of 89 trios with schizophrenic offspring and parents. Our results are not in favor of a direct involvement of the HLA system in development of schizophrenia, but are compatible with the possible existence of a susceptibility gene in the MHC region at chromosome 6p 21.31.

Molecular genetics of schizophrenia: past, present and future

Schizophrenia is a severe neuropsychiatric disorder with a polygenic mode of inheritance which is also governed by non-genetic factors. Candidate genes identified on the basis of biochemical and pharmacological evidence are being tested for linkage and association studies. Neurotransmitters, especially dopamine and serotonin have been widely implicated in its etiology. Genome scan of all human chromosomes with closely spaced polymorphic markers is being used for linkage studies. The completion and availability of the first draft of Human Genome Sequence has provided a treasure-trove that can be utilized to gain insight into the so far inaccessible regions of the human genome. Significant technological advances for identification of single nucleo-tide polymorphisms (SNPs) and use of microarrays have further strengthened research methodologies for genetic analysis of complex traits. In this review, we summarize the evolution of schizophrenia genetics from the past to the present, current trends and future direction of research.

Immune related genetic polymorphisms and schizophrenia among the Chinese

Genetic association studies were conducted among two independent cohorts of Chinese ethnicity. The samples consisted of cases and unrelated controls, ascertained from Guangzhou, China, and Singapore. The studies were prompted by our earlier report of an association between schizophrenia and HLA DQB1 alleles (HLA DQB1*0602 and HLA DQB1*0303) in the Singapore sample. Polymorphisms of HLA DQB1 and flanking markers on chromosome 6p21.3 were investigated in the first part of the study. A significant negative association with HLA DQB1*0402 was detected in the Guangzhou sample (Odds ratio, OR 0.26, 95% confidence intervals, CI 0.1, 0.6; p < 0.02, corrected for multiple comparisons). Additional analysis of the Guangzhou and Singapore samples revealed associations at three other anonymous markers flanking HLA DQB1. In the second part of the study, three polymorphisms at the Interleukin-1 gene cluster (IL-1, chromosome 2q13-q21) were investigated in both cohorts, since associations with schizophrenia have been reported in another sample. Persuasive evidence for an association at IL-1 was not detected in either sample. Our results suggest a susceptibility locus for schizophrenia in the HLA region among the Chinese, but further clarification is necessary.

Transmission disequilibrium analysis of HLA class II DRB1, DQA1, DQB1 and DPB1 polymorphisms in schizophrenia using family trios from a Han Chinese population

Our goal was to evaluate the role of HLA in the risk of developing schizophrenia, in a Han Chinese population. In several Japanese studies, there is evidence of association with DR1 and schizophrenia. A variety of other associations have been reported in other populations, including negative associations with DQbeta(*)0602 and positive associations with DR1(*)0101. Using sequence specific oligonucleotides, we genotyped four HLA markers (DRB1, DQA1, DQB1 and DPB1) in 165 family trios, consisting of Han Chinese schizophrenic subjects and their parents. Individual markers were analysed for transmission distortion in the trios using the transmission disequilibrium test. Multiple haplotype transmission was performed using the program TRANSMIT v2.5. The four markers were in strong linkage disequilibrium with each other (P value from 0.002 to 0). There was no evidence of overall transmission disequilibrium for each of the four loci. For DRB1, we did not find transmission distortion for the DRB1(*)04 and DRB1(*)08 alleles, as reported previously, but the DRB1(*)03 allele was preferentially not transmitted (P=0.009), and the DRB1(*)13 allele was preferentially transmitted from parents to schizophrenic offspring (P=0.041). Using haplotypes of pairs of markers, a significant global P value of 0.019 was achieved when using DRB1 and DQA1, mainly as a result of the excess transmission of DRB1(*)13-DQA1(*)01 (P=0.012) and a deficit in transmission of DRB1(*)03-DQA1(*)05 (P=0.002). In summary, we did not confirm any of the specific HLA allelic associations reported previously in Japanese or other populations. However, our results are compatible with the view that this region of HLA might contain a susceptibility gene which is in linkage disequilibrium with DRB1 and DQA1 genes.

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.

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.

Lack of association between schizophrenia and HLA DQB1 alleles in a Swedish sample

Three studies have reported a negative genetic association between schizophrenia and HLA DQB1*0602, an allele of the human leucocyte antigen (HLA) DQB1*06 gene. In a sample of ethnic all homogeneous Caucasians living in Sweden, the frequency of HLA DQB1 alleles in patients with schizophrenia (n = 124) was compared with that in a control group (n = 85). No significant differences were found. Together with previous investigations, the present study indicates that the reported genetic association of DQB1*0602 with schizophrenia may be limited to non-Caucasians.

Negative association of schizophrenia with HLA DQB1*0602: evidence from a second African-American cohort

The authors attempted a replication of an earlier study of African-Americans, in which they detected a negative association of schizophrenia with HLA DQB1*0602. Patients with schizophrenia (n = 75, DSM-III-R criteria) and screened adult controls of African-American ethnicity (n = 66) were genotyped with respect to HLA DQB1*0602 using a combination of two polymerase chain reaction (PCR) based assays: amplification with sequence specific primers and a dot blot assay. A significant negative association with HLA DQB1 was not noted overall, but was present among women (female patients vs. female controls: odds ratio, OR = 0.42, 95% confidence intervals, CI = 0.32, 0.55). Reanalysis of the earlier study also revealed a gender related association. When the present and earlier samples from both genders were combined, the association persisted (OR 0.48; 95% CI: 0.12, 0.52). The present findings support and association between schizophrenia and the HLA DQB1 gene locus among African-Americans.

Autoimmune diseases in the pedigrees of schizophrenic and control subjects

Autoimmune diseases aggregate in individuals and within pedigrees, and it has been postulated that autoimmune mechanisms may account for a proportion of schizophrenia. Structured questionnaires were used to interview the mothers of 121 DSM-III-R schizophrenic patients and the mothers of 116 controls in order to determine the prevalence of schizophrenia and of autoimmune diseases in their pedigrees. Patients with a schizophrenic first degree relative were significantly more likely to also have a parent or sibling with an autoimmune disease (60% vs. 20%, OR = 6.1, 95% CI = 2.3-6.5, p = 0.0003). A significant excess of insulin dependent diabetes mellitus (IDDM) was present in the parents and siblings of schizophrenic patients (OR = 9.65, 95% CI = 1.3-429.2, p = 0.009). These findings suggest that autoimmune mechanisms may play a role in the aetiology of schizophrenia, particularly familial schizophrenia. Associations have been established between autoimmune diseases and the HLA encoding genes of the major histocompatibility complex on chromosome six, and it may be that some of the genetic liability to schizophrenia involves these genes.

HLA antigens in schizophrenia and mood disorders

The frequencies of HLA antigens were examined in a sample of 75 patients with schizophrenia and 35 patients with mood disorders. We compared the data obtained from this population with data obtained in another study with 3731 healthy subjects. Statistically significant increases were observed in the frequencies of HLA A10, A11, and A29 and a statistically significant decrease was observed in the frequency of HLA A2 in patients with schizophrenia. The increased frequency in HLA B16 in patients with mood disorders was also statistically significant.

Further evidence for an association between schizophrenia and the HLA DQB1 gene locus

A case-control study was conducted in Singapore, in order to examine a proposed association between schizophrenia and the HLA DQB1 gene locus. The probands were male inpatients of Chinese ethnicity with schizophrenia (ICD-10 criteria, n = 102) and the controls were adults matched for gender and ethnicity (n = 111). Polymorphisms of the HLA DQB1 gene were examined using molecular typing by reverse dot-blotting (MTRB), a novel PCR based method. Among the patients, a positive association with HLA DQB1*0303 (odds ratio 4.46, C.I. 1.63, 12.17), as well as a negative association with HLA DQB1*0602 (odds ratio 0.22, C.I. 0.18, 0.83) was detected.

Study of the possible association of HLA class II, CD4, and CD3 polymorphisms with schizophrenia

In the present study the HLA-DRB and DPB1 alleles as well as CD4 and CD3 polymorphisms were tested in 100 Belgian schizophrenic patients and 204 controls. Our results indicate a significant negative association of the DPB1 0101 allele with schizophrenia (relative risk [RR] = 0.27). Furthermore a significant positive and negative association could be noticed for the CD4*A4 allele and CD4*A7/A8 genotype, respectively (RR 1.79 and 0.47, respectively). These findings suggest that some contribution of HLA class II and CD4 genes to an autoimmune-like pathogenesis in schizophrenia might exist.

HLA-DR types in Japanese schizophrenics: analysis by group-specific PCR amplification

An association of HLA-DR8 and DR1 with DSM-III schizophrenia has been reported in Japan (Miyanaga et al. (1984) Biol. Psychiatr. 19, 121-129). To further investigate this preliminary finding, we compared HLA-DR types in 44 unrelated Japanese schizophrenics (DSM-III-R) with those in 51 unrelated, healthy Japanese volunteers. Group-specific PCR amplification was used in the determination of HLA-DR in the patients. No significant difference was observed in the frequency of any DR types between patients and controls, after statistical correction for multiple testing. However, the frequency of DR1 in our patients (23%) and controls (10%) was almost the same as those in the previous report (22% vs. 10%), which means that there is a suggestive trend which could become significant if numbers were larger. It is argued that an exact determination of HLA-DR by DNA typing is important in current HLA studies of schizophrenia.

Association study of schizophrenia with dopamine D3 receptor gene polymorphisms: probable effects of family history of schizophrenia?

Using a case-control design, a reported association of schizophrenia with homozygosity at the dopamine D3 receptor gene locus was investigated in a group of patients (n = 53), with schizophrenia (DSM-III-R), and psychiatrically normal controls (n = 61), matched for ethnicity and area of residence. No significant differences in the distribution of alleles or genotypes between the two groups could be detected. However, among patients with a family history of schizophrenia, as compared to controls without such family history, an association with allele 1 at this locus was noted (Odds ratio 12.4, C.I. 1.61, 96.35).

Autoimmunity in schizophrenia: a review of recent findings

The pathophysiology of psychotic and other symptoms in schizophrenia remains a mystery despite decades of research. Even though it has been suspected for many years that autoimmune mechanisms may play a role in the pathophysiology of schizophrenia, firm evidence for this hypothesis has been lacking. Our studies, over the last 10 years, have revealed that a subgroup of schizophrenics have several significant immunological abnormalities, including increased prevalence of autoimmune diseases and of antinuclear antibodies (ANA) and anticytoplasmic antibodies (ACA), decreased lymphocyte interleukin-2 (IL-2) production, increased serum IL-2 receptor concentration, increased serum IL-6 concentration, and an association with HLA antigens. These findings are characteristic of autoimmune diseases such as systemic lupus erythematosus (SLE), rheumatoid arthritis and insulin-dependent diabetes mellitus. We also found that some schizophrenics have antibodies to hippocampal antigens (AHA) in their serum, together with lowered IL-2 production. None of the above findings can be interpreted as definitely confirming the role of autoimmunity in schizophrenia. Nevertheless, taken together, the recent evidence points towards the existence of a subgroup of schizophrenics who have immunological findings consistent with that hypothesis. Further studies directed at finding the brain antigens targeted by the immune system in these patients, and longitudinal studies correlating clinical and immune changes over time, are needed.