The mGlu5 Receptor Protomer-Mediated Dopamine D2 Receptor Trans-Inhibition Is Dependent on the Adenosine A2A Receptor Protomer: Implications for Parkinson's Disease.

The adenosine A2A receptor (A2AR), dopamine D2 receptor (D2R) and metabotropic glutamate receptor type 5 (mGluR5) form A2AR-D2R-mGluR5 heteroreceptor complexes in living cells and in rat striatal neurons. In the current study, we present experimental data supporting the view that the A2AR protomer plays a major role in the inhibitory modulation of the density and the allosteric receptor-receptor interaction within the D2R-mGluR5 heteromeric component of the A2AR-D2R-mGluR5 complex in vitro and in vivo. The A2AR and mGluR5 protomers interact and modulate D2R protomer recognition and signalling upon forming a trimeric complex from these receptors. Expression of A2AR in HEK293T cells co-expressing D2R and mGluR5 resulted in a significant and marked increase in the formation of the D2R-mGluR5 heteromeric component in both bioluminescence resonance energy transfer and proximity ligation assays. A highly significant increase of the the high-affinity component of D2R (D2RKi High) values was found upon cotreatment with the mGluR5 and A2AR agonists in the cells expressing A2AR, D2R and mGluR5 with a significant effect observed also with the mGluR5 agonist alone compared to cells expressing only D2R and mGluR5. In cells co-expressing A2AR, D2R and mGluR5, stimulation of the cells with an mGluR5 agonist like or D2R antagonist fully counteracted the D2R agonist-induced inhibition of the cAMP levels which was not true in cells only expressing mGluR5 and D2R. In agreement, the mGluR5-negative allosteric modulator raseglurant significantly reduced the haloperidol-induced catalepsy in mice, and in A2AR knockout mice, the haloperidol action had almost disappeared, supporting a functional role for mGluR5 and A2AR in enhancing D2R blockade resulting in catalepsy. The results represent a relevant example of integrative activity within higher-order heteroreceptor complexes.

Antipsychotic-Like Efficacy of Dopamine D2 Receptor-Biased Ligands is Dependent on Adenosine A2A Receptor Expression.

Dopamine D2 receptor (D2R) activation triggers both G protein- and ß-arrestin-dependent signaling. Biased D2R ligands activating ß-arrestin pathway have been proposed as potential antipsychotics. The ability of D2R to heteromerize with adenosine A2A receptor (A2AR) has been associated to D2R agonist-induced ß-arrestin recruitment. Accordingly, here we aimed to demonstrate the A2AR dependence of D2R/ß-arrestin signaling. By combining bioluminescence resonance energy transfer (BRET) between ß-arrestin-2 tagged with yellow fluorescent protein and bimolecular luminescence complementation (BiLC) of D2R/A2AR homomers and heteromers, we demonstrated that the D2R agonists quinpirole and UNC9994 could promote ß-arrestin-2 recruitment only when A2AR/D2R heteromers were expressed. Subsequently, the role of A2AR in the antipsychotic-like activity of UNC9994 was assessed in wild-type and A2AR-/- mice administered with phencyclidine (PCP) or amphetamine (AMPH). Interestingly, while UNC9994 reduced hyperlocomotion in wild-type animals treated either with PCP or AMPH, in A2AR-/- mice, it failed to reduce PCP-induced hyperlocomotion or produced only a moderate reduction of AMPH-mediated hyperlocomotion. Overall, the results presented here reinforce the notion that D2R/A2AR heteromerization facilitates D2R ß-arrestin recruitment, and furthermore, reveal a pivotal role for A2AR in the antipsychotic-like activity of the ß-arrestin-biased D2R ligand, UNC9994.

Untangling dopamine-adenosine receptor-receptor assembly in experimental parkinsonism in rats.

Parkinson's disease (PD) is a dopaminergic-related pathology in which functioning of the basal ganglia is altered. It has been postulated that a direct receptor-receptor interaction - i.e. of dopamine D2 receptor (D2R) with adenosine A2A receptor (A2AR) (forming D2R-A2AR oligomers) - finely regulates this brain area. Accordingly, elucidating whether the pathology prompts changes to these complexes could provide valuable information for the design of new PD therapies. Here, we first resolved a long-standing question concerning whether D2R-A2AR assembly occurs in native tissue: by means of different complementary experimental approaches (i.e. immunoelectron microscopy, proximity ligation assay and TR-FRET), we unambiguously identified native D2R-A2AR oligomers in rat striatum. Subsequently, we determined that, under pathological conditions (i.e. in a rat PD model), D2R-A2AR interaction was impaired. Collectively, these results provide definitive evidence for alteration of native D2R-A2AR oligomers in experimental parkinsonism, thus conferring the rationale for appropriate oligomer-based PD treatments.

Uncovering caffeine's adenosine A2A receptor inverse agonism in experimental parkinsonism.

Caffeine, the most consumed psychoactive substance worldwide, may have beneficial effects on Parkinson's disease (PD) therapy. The mechanism by which caffeine contributes to its antiparkinsonian effects by acting as either an adenosine A2A receptor (A2AR) neutral antagonist or an inverse agonist is unresolved. Here we show that caffeine is an A2AR inverse agonist in cell-based functional studies and in experimental parkinsonism. Thus, we observed that caffeine triggers a distinct mode, opposite to A2AR agonist, of the receptor's activation switch leading to suppression of its spontaneous activity. These inverse agonist-related effects were also determined in the striatum of a mouse model of PD, correlating well with increased caffeine-mediated motor effects. Overall, caffeine A2AR inverse agonism may be behind some of the well-known physiological effects of this substance both in health and disease. This information might have a critical mechanistic impact for PD pharmacotherapeutic design.

Majorcan Black Pig as a traditional pork production system: improvements in slaughterhouse procedures and elaboration of pork carpaccio as an alternative product.

The Majorcan Black Pig (MBP) was used as a model of differentiated traditional system within the Q-PorkChains project. The MBP farms were taken as an example of traditional system using a local breed which claims for high meat quality products. Welfare Quality® protocol was applied at the slaughterhouse and improvement strategies related to ante-mortem conditions and technological meat quality were defined. Pork carpaccio from MBP was elaborated to evaluate its sensory properties as an alternative to the existing MBP products. MBP tenderloins were better suited than those from pigs from a commercial breed to elaborate this product.

Ras-association domain of sorting Nexin 27 is critical for regulating expression of GIRK potassium channels.

G protein-gated inwardly rectifying potassium (GIRK) channels play an important role in regulating neuronal excitability. Sorting nexin 27b (SNX27b), which reduces surface expression of GIRK channels through a PDZ domain interaction, contains a putative Ras-association (RA) domain with unknown function. Deleting the RA domain in SNX27b (SNX27b-ΔRA) prevents the down-regulation of GIRK2c/GIRK3 channels. Similarly, a point mutation (K305A) in the RA domain disrupts regulation of GIRK2c/GIRK3 channels and reduces H-Ras binding in vitro. Finally, the dominant-negative H-Ras (S17N) occludes the SNX27b-dependent decrease in surface expression of GIRK2c/GIRK3 channels. Thus, the presence of a functional RA domain and the interaction with Ras-like G proteins comprise a novel mechanism for modulating SNX27b control of GIRK channel surface expression and cellular excitability.

Cured meat consumption increases risk of readmission in COPD patients.

Recent studies have shown that a high dietary intake of cured meat increases the risk of chronic obstructive pulmonary disease (COPD) development. However, its potential effects on COPD evolution have not been tested. We aimed to assess the association between dietary intake of cured meat and risk of COPD readmission in COPD patients. 274 COPD patients were recruited during their first COPD admission between 2004 and 2006, provided information on dietary intake of cured meat during the previous 2 yrs, and were followed until December 31, 2007 (median follow-up 2.6 yrs). Associations between cured meat intake and COPD admissions were assessed using parametric regression survival-time models. Mean ± SD age was 68 ± 8 yrs, 93% of patients were male, 42% were current smokers, mean post-bronchodilator forced expiratory volume in 1 s (FEV(1)) was 53 ± 16% predicted, and median cured meat intake was 23 g · day(-1). After adjusting for age, FEV(1), and total caloric intake, high cured meat intake (more than median value) increased the risk of COPD readmission (adjusted HR 2.02, 95% CI 1.31-3.12; p=0.001). High cured meat consumption increases the risk of COPD readmission in COPD patients. The assessment of the effectiveness of healthy diet advice should be considered in the future.

Association between Ω3 and Ω6 fatty acid intakes and serum inflammatory markers in COPD.

Dietary intake of polyunsaturated fatty acids, including omega-3 and omega-6, could modulate chronic obstructive pulmonary disease (COPD) persistent inflammation. We aimed to assess the relationship between dietary intake of omega-3 and omega-6 fatty acids and serum inflammatory markers in COPD. A total of 250 clinically stable COPD patients were included. Dietary data of the last 2 years were assessed using a validated food frequency questionnaire (122 items), which provided levels of three omega-3 fatty acids: docosahexaenoic acid, eicosapentaenoic acid and α-linolenic acid (ALA); and two omega-6 fatty acids: linoleic acid and arachidonic acid (AA). Inflammatory markers [C-reactive protein (CRP), interleukin (IL)-6, IL-8 and tumor necrosis factor alpha (TNFα)] were measured in serum. Fatty acids and inflammatory markers were dichotomised according to their median values, and their association was assessed using multivariate logistic regression. Higher intake of ALA (an anti-inflammatory omega-3 fatty acid) was associated with lower TNFα concentrations [adjusted odds ratio (OR)=0.46; P=.049]. Higher AA intake (a proinflammatory omega-6 fatty acid) was related to higher IL-6 (OR=1.96; P=.034) and CRP (OR=1.95; P=.039) concentrations. Therefore, this study provides the first evidence of an association between dietary intake of omega-3 and omega-6 fatty acids and serum inflammatory markers in COPD patients.

T regulatory cells distinguish two types of primary hypophysitis.

Numerous cases of primary hypophysitis have been described over the past 25 years with, however, little insight into the cause(s) of this disease. In order to guide treatment, a better understanding of the pathogenesis is needed. We studied the pathogenesis of primary hypophysitis by analysing systematically the immune response at the pituitary tissue level of consecutive cases of 'lymphocytic' hypophysitis who underwent pituitary biopsy. In order to investigate further the pathogenesis of their diseases we characterized two cases at clinical, cellular and molecular levels. We show here, for the first time, that lymphocytic hypophysitis probably encompasses at least two separate entities. One entity, in agreement with the classical description of lymphocytic hypophysitis, demonstrates an autoimmune process with T helper 17 cell dominance and lack of T regulatory cells. The other entity represents a process in which T regulatory cells seem to control the immune response, which may not be self- but foreign-targeted. Our data suggest that it may be necessary to biopsy suspected primary hypophysitis and to analyse pituitary tissue with immune markers to guide treatment. Based on our results, hypophysitis driven by an immune homeostatic process should not be treated with immunosuppression, while autoimmune-defined hypophysitis may benefit from it. We show here for the first time two different pathogenic processes classified under one disease type and how to distinguish them. Because of our findings, changes in current diagnostic and therapeutic approaches may need to be considered.

[The WSH percutaneous spine fixation device. Actual results and future expectations]. / Le système d'arthrodèse percutanée WSH. Resultats actuels et perspectives de développement futur.

BACKGROUND AND PURPOSE: The purpose of this study was to report our initial experience with a new percutaneous spine fixation system, avoiding open exposure, excessive blood loss and extensive muscle dissection. With the specially designed plates, this system can be used whatever the conformation of the segment instrumented is kyphotic or lordotic. METHODS: Sixteen patients (9 men and 7 women ranging in age from 27 to 78 years, mean 54.9) underwent percutaneous pedicle fixation using this device. Twelve patients underwent single level fusions (discogenic lowback pain in 6 cases, spondylolisthesis in 1), and 4 underwent two-level fusions (2 for lumbar fracture and 2 for spondylolisthesis). TLIF by intersomatic cages were inserted at the same time in two patients with spondylolisthesis. The follow-up period ranged from 3 to 15 months (mean 5 months). RESULTS: Improvement in pain control was assessed using a specially designed scale, allowing qualitative self-evaluation of pain control. Pain control was excellent in 12 patients, good in 3 and poor in one case due to loss of independence related to multiple associated disabling conditions. CONCLUSIONS: Percutaneous pedicule screw insertion using this device is a safe and reliable technique. Further improvements in the system which allows a certain degree of spinal mobility after screw placement are in process. Early results shown in this study illustrate the perspectives.

[Mortality due to asthma in the city of Barcelona (1983-1993)]. / Mortalidad por asma en la ciudad de Barcelona (1983-1993).

OBJECTIVE: To find asthma mortality in the city of Barcelona. DESIGN: Descriptive study of mortality. SETTING: City of Barcelona. MAIN MEASUREMENTS: Deaths due to asthma in the city of Barcelona in the period 1983-1993 were studied through the register of mortality at Barcelona's Municipal Institute of Health, which in turn is supplied by the Statistical Gazette of Deaths. Rates of mortality per 100,000 inhabitants were calculated, overall and broken down by sex and by age. The ratio of mortality comparing city districts and the place and season of decease was also worked out. RESULTS: There were 716 deaths due to asthma (overall rate of 3.82/100,000 inhabitants; 3.3 in men and 4.33 in women). Almost two-thirds of deaths occurred in people over 65. Mortality was stable in the entire period except in the over-65s, in which a downwards trend was discerned (beta=-0.63; P=.037). For the 5-34 year old group, the rate oscillated between 0.1 and 0.6/100,000 inhabitants. The number of deaths in the over-65s was greater in winter (31.7%; 95% CI, 27.8-35.7). 56.2% of deaths occurred at home. Hospital deaths were more common among women (P<.001) and the under-65s, and their trend is upwards (P=.004). CONCLUSIONS: Asthma mortality in the city of Barcelona was stable during the period studied. Its rate for the 5-34 year-old age group was higher than for Spain and slightly greater than in similar nearby countries.

Mortalidad por asma en la ciudad de Barcelona (1983-1993) / Mortality du to asthma in the city of Barcelona (1983-1993)

Objetivo. Conocer la mortalidad por asma en la ciudad de Barcelona. Diseño. Estudio descriptivo de mortalidad. Emplazamiento. Ciudad de Barcelona. Mediciones principales. A través del registro de mortalidad del Instituto Municipal de la Salud de Barcelona, que se nutre del Boletín Estadístico de Defunción (BED), se estudian los fallecidos por asma en el período 1983-1993 en la ciudad de Barcelona. Se calculan las tasas de mortalidad por 100.000 habitantes, crudas y específicas por sexo, y las estandarizadas por edad; y la razón de mortalidad comparativa (RMC) entre los distritos de la ciudad y el lugar y la época del año del fallecimiento. Resultados. Hubo 716 fallecimientos por asma (tasa global de 3,82/100.000 habitantes; 3,3 en los varones y 4,33 en las mujeres). Casi dos tercios de los fallecimientos se produjeron en personas mayores de 65 años. La mortalidad se ha mantenido estable en todo el período, excepto en el grupo mayor de 65 años, en el que se detecta una tendencia a su disminución ( = -0,63; p = 0,037). Para el grupo de 5-34 años la tasa oscila entre 0,1 y 0,6/100.000 habitantes. El número de fallecimientos fue mayor en invierno en los mayores de 65 años (31,7 por ciento; intervalo de confianza del 95 por ciento, 27,8-35,7). El 56,2 por ciento de los fallecimientos suceden en el domicilio; las muertes en el hospital son más frecuentes entre mujeres (p < 0,001) y en menores de 65 años, y su tendencia es creciente (p = 0,004).Conclusiones. La mortalidad por asma en la ciudad de Barcelona es estable en el período de estudio y presenta una tasa para el grupo de 5-34 años más alta que en España y ligeramente mayores que las de los países de nuestro entorno (AU)

Isolation and characterization of human monoclonal autoantibodies to glutamic acid decarboxylase.

Production of human monoclonal autoantibodies to glutamic acid decarboxylase M(r) 65,000 (GAD65), characterization of their isotype, binding affinity, V region sequences and competition with autoantibodies in patients' sera is described. Lymphocytes from a patient with Addison's disease who had GAD65 autoantibodies without diabetes were immortalised and fused to a mouse/human hybridoma. In addition, mouse monoclonal antibodies to GAD65 were produced using standard techniques. F(ab')2S from our monoclonals and the GAD6 mouse monoclonal were used in competition with intact monoclonals and sera from diabetic patients for binding to 125I-labelled GAD65 (amino acids 46-586). Reactivities of the human monoclonals with GAD 65,000/67,000 M(r) chimeras were also studied. Variable region genes of human monoclonals were sequenced and analysed. The human monoclonals (n = 3) had affinity constants for GAD65 of 2.2 x 10(9), 5.8 x 10(9), 1.3 x 10(10) mol/l(-1); affinities of the mouse monoclonals (n = 5) ranged from 1.1 x 10(8) to 5.4 x 10(10) mol/l(-1). The binding of each of the human monoclonals was inhibited by GAD6 F(ab')2 and the binding of GAD6 antibody was inhibited by the human monoclonal F(ab')2S suggesting that the epitopes for these antibodies were overlapping. Studies with GAD65/GAD67 chimeras indicated that the human monoclonals reacted with C-terminal epitopes. The human monoclonals, GAD6 and 3/5 mouse monoclonals inhibited serum autoantibody binding to 125I-labelled GAD65. Overall, the human monoclonals were of high affinity, reacted with C-terminal epitopes and showed evidence of antigen driven maturation; they represented only a proportion of the repertoire of autoantibodies to GAD65 in the donor's serum and in the sera of patients with type-1 diabetes.

Cytokines, IgG subclasses and costimulation in a mouse model of thyroid autoimmunity induced by injection of fibroblasts co-expressing MHC class II and thyroid autoantigens.

AKR/N mice injected with fibroblasts expressing MHC class II (RT4.15HP cells) and the TSH receptor (TSHR) develop antibodies similar to those in Graves' disease. We were unable to analyse the subclass of these antibodies because of unexpectedly high non-specific binding by ELISA or flow cytometry. The non-specific binding reflected generalized immune activation which occurred even when the fibroblasts did not express the TSHR. However, the IgG subclasses were determined for thyroid peroxidase (TPO) antibodies induced using TPO-expressing RT4.14HP cells and found to be IgG2a > IgG1. This Thl pattern is consistent with spontaneous secretion of interferon-gamma (but not IL-4 or IL-10) by splenocytes from injected mice. The Th1 bias was related to fibroblast injection because conventional immunization of the same mouse strain with purified TPO and adjuvant induced a Th2 response (IgG1 >> IgG2a). Further, untransfected fibroblasts themselves induced powerful, non-specific proliferative responses when used as antigen-presenting cells (APC) in vitro. Flow cytometry revealed that the RT4.15HP fibroblasts (and TSHR- and TPO-transfected derivatives) expressed B7-1. Unexpected constitutive expression of this key molecule may bypass the requirement for up-regulation of other costimulatory molecules involved in T cell stimulation. Our data support the concept that RT4.15HP fibroblasts present the TSHR (or TPO), at least for initiating the immune response. However, the accompanying generalized immune stimulation creates difficulties for analysis of TSHR-specific T and B lymphocytes. On the other hand, extension of the model to TPO, an easier antigen to study, will facilitate analysis of murine T cell responses likely to resemble those in human thyroid autoimmunity.

Development of overt autoimmune hyperthyroidism in a patient therapeutically immunosuppressed after liver transplantation.

Immunosuppression is a therapeutic maneuver directed at preventing transplant rejection. When applied to autoimmunity, immunosuppression is intended to target similar immune processes. We report an unusual case of a 35-year-old woman who developed autoimmune hyperthyroidism of Graves' disease while on immunosuppressive therapy for liver transplantation. Signs and symptoms of hyperthyroidism were already present when, misled by the concomitant toxic hepatic syndrome, liver rejection was first suspected. Despite a therapeutic level of cyclosporine, elevated serum alanine and aspartate aminotransferase levels were noted. Consequently, a liver biopsy was performed to exclude an acute rejection. The findings were consistent with acute hepatitis without evidence of rejection. Then, the diagnosis of Graves' hyperthyroidism was considered and finally confirmed by finding a suppressed thyroid-stimulating hormone, elevated thyroid hormone levels, and a high and homogeneous thyroid uptake from radioactive iodine scan. Thyroid peroxidase antibody and thyroid-stimulating immunoglobulin were markedly elevated. The patient was treated with radioactive iodine, which resulted in improvement of symptoms and resolution of abnormal liver function tests. Although the mechanisms involved in transplant rejection and human autoimmunity are thought to be similar, the development of Graves' disease in this patient despite therapeutic immunosuppression suggests that the immunological processes may be different.

Rarity of autoantibodies to a major autoantigen, thyroid peroxidase, that interact with denatured antigen or with epitopes outside the immunodominant region.

The nature of the autoantibody repertoire to the dominant autoantigen in human autoimmune thyroid disease is controversial. There is evidence that autoantibodies to thyroid peroxidase (TPO) interact with overlapping conformational epitopes in an immunodominant region and binding to denatured (DN) protein is decreased. Contrary data demonstrate TPO autoantibody reactivity with DN-TPO or polypeptide fragments. However, none of the TPO-specific, human monoclonal autoantibodies isolated to date preferentially recognize denatured autoantigen. We therefore searched an immunoglobulin gene phage display library for human autoantibodies that bind TPO denatured by reduction and alkylation (DN-TPO). Thyroid-infiltrating B cells from a typical TPO autoantibody-positive patient were the source of mRNA for library construction. Surprisingly, the library enriched after panning on DN-TPO, as well as a panel of individual clones, preferentially bound native (N)-TPO. Of 13 clones selected using DN-TPO or N-TPO, 12 clones recognized the TPO immunodominant region. Moreover, regardless of selection with N-TPO or DN-TPO, their heavy and light chains were encoded by similar VDJ and Vkappa combinations. One clone (DN4), isolated using DN-TPO, did not interact with the TPO immunodominant region and its H chain derives from a different VH gene. Although DN4 binds specifically to TPO, its affinity is low, unlike the high affinities of other human TPO autoantibodies. In conclusion, human monoclonal autoantibodies that preferentially recognize denatured TPO could not be isolated from an immunoglobulin gene library despite selection with denatured protein. Our findings demonstrate the bias of the human B cell repertoire towards recognition of an immunodominant region on the conformationally intact form of a major thyroid autoantigen.

Cellular thyroid peroxidase (TPO), unlike purified TPO and adjuvant, induces antibodies in mice that resemble autoantibodies in human autoimmune thyroid disease.

Autoantibodies to several protein antigens in human autoimmunity interact with a restricted range of epitopes, whereas diverse epitopes are recognized by antibodies induced in animals using antigen and adjuvant. To examine the basis for this difference, we compared the qualitative nature of antibodies developing in AKR/N mice injected with purified thyroid peroxidase (TPO) and adjuvant or with TPO expressed on major histocompatibility complex (MHC) class II+ fibroblasts. Mice injected with purified TPO had higher TPO antibody levels than TPO+/class II+ fibroblast-treated mice. Despite lower titers, recipients of TPO+/class II+ cells developed very high affinity antibodies (Kd = approximately 10(-10) M), comparable with those of human TPO autoantibodies and about 10-fold higher than those in purified TPO plus adjuvant-immunized mice. Moreover, more than 90% of TPO antibodies in TPO+/class II+ fibroblast-injected mice, compared with only approximately 50% in TPO plus adjuvant-immunized mice, were to the immunodominant region recognized by patients' autoantibodies. Consistent with this epitopic restriction, TPO+/class II+ fibroblast-injected mice had TPO antibody epitopic fingerprints similar to those of human autoantibodies. In conclusion, mice injected with TPO+/class II+ fibroblasts, but not those injected with purified TPO and adjuvant, develop antibodies closely resembling autoantibodies in human disease. These observations indicate that some animal models based on conventional immunization may not be representative of human diseases with a major humoral component.

Evidence for genetic transmission of thyroid peroxidase autoantibody epitopic "fingerprints".

Autoimmune thyroid disease is characterized by the tendency to cluster in families and by IgG class autoantibodies to antigens such as thyroid peroxidase (TPO). The epitopes recognized by polyclonal serum autoantibodies can be quantitatively fingerprinted using four recombinant human TPO autoantibodies (expressed as Fab) that define A and B domain epitopes in an immunodominant region. To determine whether these fingerprints are genetically transmitted, we analyzed fingerprints of 63 members of 7 multiplex Old Order Amish families and 17 individuals from 4 Hashimoto thyroiditis families. Inhibition of serum autoantibody binding to [125I]TPO by the recombinant Fab was used to assess recognition of the TPO immunodominant region (4 Fab combined) and recognition of domain A or B (individual Fab). Complex segregation analysis was performed using a unified model (POINTER). For the 4 Fab combined inhibition phenotype, the no transmission model was rejected (chi2(4) = 20.67; P < 0.0032), and the most parsimonious model includes a major gene effect. More importantly, evidence for genetic transmission was obtained for the phenotype defined by the ratio of inhibition by subdomain Fab B1:B2. Thus, for this ratio (reflecting recognition of the B domain), the no transmission model was rejected chi2(4) = 63.59; P < 0.000008). Moreover, the polygenic hypothesis could be rejected, but not the major locus hypothesis, suggesting that major genes might be involved in familial transmission of this trait. In conclusion, our findings suggest that autoantibody recognition of the TPO immunodominant region and the TPO B domain is genetically transmitted. These data may open the way to the identification by candidate analysis or positional cloning of at least one gene responsible for the development of Hashimoto's thyroiditis.