Identification of antigenic domains on the human sodium-iodide symporter which are recognized by autoantibodies from patients with autoimmune thyroid disease

The sodium-iodide symporter (NIS) is a novel autoantigen in autoimmune thyroid disease. In the present study we have characterized the antigenic domains on the human symporter which are recognized by autoantibodies from patients with either Graves' disease (GD) or autoimmune hypothyroidism (AH). Deletion derivatives of complementary DNA (cDNA) encoding the Na(+)/I(-) symporter were constructed using polymerase chain reaction (PCR) amplification. These deletion constructs were translated in vitro with the concomitant incorporation of [(35)S]methionine into the protein products. The reactivity of seven GD and six AH sera, which were known to contain symporter-binding antibodies, to each of the radiolabelled modified symporters was then determined in immunoprecipitation experiments. Analyses of the results obtained in the radiobinding assays suggest the existence of multiple antibody binding sites on human NIS (hNIS), including regions between amino acids (aa) 1--134, 191--286, 290--411, 411--520 and 520--588. Computer prediction of the potential B cell epitopes on the symporter revealed that, apart from aa 134--191, all the epitope domains identified overlapped, at least in part, with areas predicted to be highly antigenic. Interestingly, the antigenic domains represented by aa 191--286, 290--411 and 411--520 include regions of the polypeptide which form putative extracellular domains in the secondary structure model of the rat symporter. No correlation between the recognition of specific epitopes on the human symporter and the type of autoimmune thyroid disease was demonstrated.

Molecular mapping of epitopes on melanocyte-specific protein Pmel17 which are recognized by autoantibodies in patients with vitiligo

Previously, we reported the identification of Pmel17 autoantibodies in some patients with vitiligo. Here, we have determined the B cell epitopes on Pmel17 which are recognized by these autoantibodies. Deletion derivatives of Pmel17 cDNA were constructed using either subcloning of specific cDNA fragments or polymerase chain reaction amplification. Full-length Pmel17 cDNA and its truncated derivatives were then translated in vitro to produce [(35)S]-labelled proteins. The radiolabelled ligands were used subsequently in radiobinding assays to investigate the reactivity of sera from vitiligo patients. Two epitope regions were identified: one located at the C-terminal end of Pmel17 between amino acids 634--644 and one in a central region of the protein between amino acids 326--341. Computer analysis of the potential B cell epitopes on Pmel17 revealed that the epitope domain encompassing amino acids 326--341 was located in an area of the protein which was predicted to be highly antigenic. In contrast, the epitope identified at the C-terminal of Pmel17 (amino acids 634--644) was located in a region of the protein predicted to have low antigenicity. The amino acid sequences of the identified Pmel17 epitopes were compared to the amino acid sequences of the related melanogenic enzymes tyrosinase, tyrosinase-related protein-1 and tyrosinase-related protein-2. However, no sequence homology was found between either of the Pmel17 epitopes and the aforementioned proteins. This finding is consistent with our previous study in which we were unable to show the presence of Pmel17 antibodies which were cross-reactive with either tyrosinase, tyrosinase-related protein-1 or tyrosinase-related protein-2. It also suggests that the IgG response to Pmel17 is distinct from the antibody response to the other melanocyte-specific antigens.

Autoantibodies to the flavoprotein subunit of succinate dehydrogenase: analysis of specificity in autoimmune thyroid disease

OBJECTIVE

Thyroid-associated ophthalmopathy is a progressive eye disorder affecting the extraocular muscle and orbital connective tissue and is considered to have an autoimmune aetiology. A recent study reported a close relationship between serum antibodies against the flavoprotein subunit of succinate dehyhdrogenase (SDHFp) and active thyroid-associated ophthalmopathy involving eye muscle damage. The aim of the present study was to develop a sensitive and quantitative radiobinding assay for the detection of antibodies to the flavoprotein subunit of succinate dehydrogenase and to use this to determine the distribution of antibodies in different patient groups.

DESIGN AND PATIENTS

Serum samples from the following patient groups were analysed: 20 systemic lupus erythematosus; 20 Addison's disease; 26 autoimmune hypothyroidism; 28 Graves' hyperthyroidism; 12 pretibial myxoedema; 25 thyroid-associated ophthalmopathy. Sera from 20 healthy subjects were used as controls. [35S]-labelled succinate dehydrogenase flavoprotein was produced in an in vitro transcription-translation system and subsequently used in immunoprecipitation experiments with sera from patient and control groups to test for the presence of antibodies to the flavoprotein.

RESULTS

Succinate dehydrogenase flavoprotein antibodies were detected in five of the 20 (25%) patients with Addison's disease, six of the 20 (30%) with systemic lupus erythematosus, five of the 26 (19%) with autoimmune hypothyroidsm, six of the 28 (21%) with Graves' hyperthyroidism, two of the 12 (17%) with pretibial myxoedema and three of the 25 (12%) with thyroid-associated ophthalmopathy. The frequencies of flavoprotein antibodies were significantly greater than controls (P-value < 0.05) for patients with systemic lupus erythematosus (P = 0.02), but not for patients with either Addison's disease (P = 0.05), pretibial myxoedema (P = 0.13), Graves' hyperthyroidism (P = 0.07), autoimmune hypothyroidism (P = 0.06) or thyroid-associated ophthalmopathy (P = 0.24). For the patients with thyroid-associated ophthalmopathy, the frequency of SDHFp antibodies did not appear to be related to the length of time from diagnosis: the group containing samples taken less than one year from diagnosis showed no increased frequency of SDHFp antibodies when compared to controls (P = 0.10), with three of the 18 (17%) patients being positive. With respect to seven patients with thyroid-associated ophthalmopathy diagnosed for more than a year, SDHFp antibodies were not detected in any of their serum samples. In addition, the clinical severity of the disease, as recorded by the NOSPECS classification, did not correlate with the frequency of SDHFp antibodies: P = 0.13, 0.33 and 0.38, respectively, for patients with Grade II, III and IV ophthalmopathy. Similar results were also found in the case of patients with pretibial myxoedema and eye disease: P = 0.06 for patients with Grade III ophthalmopathy and, SDHFp antibodies were not detected in any of the sera taken from patients with Grade IV ophthalmopathy. In addition, no association was found between disease duration and the frequency of antibodies to the flavoprotein in this patient group.

CONCLUSIONS

Our results indicate that succinate dehydrogenase flavoprotein antibodies are not a suitable marker for thyroid-associated ophthalmopathy, at least with the assay system used, as they can be found in patients who do not have eye disease and therefore lack the disease specificity required of a diagnostic tool.

Detection of binding and blocking autoantibodies to the human sodium-iodide symporter in patients with autoimmune thyroid disease

The sodium iodide symporter (NIS) is a novel autoantigen in autoimmune thyroid disease (ATD). A recent study has described the development of a bioassay for human (h) NIS antibody detection, but this will not detect antibodies that bind the symporter without modulating its activity. Therefore, the establishment of a binding assay is of importance to determine the overall prevalence of hNIS antibodies in ATD patients. An in vitro transcription and translation system was used to produce [35S]-labeled hNIS. The radiolabeled ligand reacted specifically in immunoprecipitation experiments with rabbit antiserum raised against a peptide fragment of hNIS. Subsequently, the reactivity of control and ATD sera to translated [35S]hNIS was determined using RIAs. A significant difference in the frequency of hNIS antibody-positive sera was found when patients with either Graves' disease (GD) or autoimmune hypothyroidism (AH) were compared with normal controls (P = 0.01 and P = 0.03, respectively). Of 49 GD and 29 AH sera tested, 11 (22%) and 7 (24%), respectively, were found to contain hNIS antibodies. Differences were also significant when the antibody-binding indices of the control group of sera were compared with those of both the GD and the AH patient sera (P < 0.0001 and P = 0.001, respectively). In contrast, sera from 10 patients with Addison's disease and 10 patients with vitiligo (without associated ATD) were all negative for antibody reactivity to the symporter. No differences were detected when the antibody binding indices of either the Addison's disease or the vitiligo sera were compared with those of the normal sera group (P = 0.9 and P = 0.6, respectively). Eight of the 11 (73%) GD and 3 of the 7 (43%) AH sera, which were positive for hNIS antibodies in the immunoprecipitation assay, were also found to inhibit iodide uptake in hNIS-transfected CHO-K1 cells, suggesting the existence of antibodies in some serum samples that bind to the symporter without modulating its function. Overall, a significant correlation was found between the iodide uptake inhibition and the binding assays for hNIS antibody detection (r = 0.49, P < 0.0001). In summary, we have developed a specific and quantitative assay for the detection of hNIS binding antibodies in sera of patients with ATD. This system offers the advantage of studying antibody reactivity against conformational epitopes and will be useful in understanding the role of NIS autoreactivity in the pathogenesis of ATD.

Association analysis of the cytotoxic T lymphocyte antigen-4 (CTLA-4) and autoimmune regulator-1 (AIRE-1) genes in sporadic autoimmune Addison's disease

Although autoimmune Addison's disease (AAD) may occur as a component of the monogenic autoimmune polyendocrinopathy type 1 syndrome (APS1), it is most commonly found as an isolated disorder or associated with the autoimmune polyendocrinopathy type 2 syndrome (APS2). It is likely that sporadic (non-APS1) AAD is inherited as a complex trait; however, apart from the major histocompatibility complex, the susceptibility genes remain unknown. We have examined polymorphisms at two non-major histocompatibility complex candidate susceptibility loci in sporadic (non-APS1) AAD: the cytotoxic T lymphocyte antigen-4 (CTLA-4) gene and the autoimmune regulator (AIRE-1) gene. DNA samples from AAD subjects (n = 90) and local controls (n = 144 for CTLA-4; n = 576 for AIRE-1) were analyzed for the CTLA-4A/G polymorphism in exon 1 of the CTLA-4 gene and for the common mutant AIRE-1 allele (964de113) in United Kingdom subjects with APS1, by using the restriction enzymes Bst7II and BsrBI, respectively. There was an association of the G allele at CTLA-4A/G in AAD subjects (P = 0.008 vs. controls), which was stronger in subjects with AAD as a component of APS2 than in subjects with isolated AAD. In contrast, the mutant AIRE-1 964del13 allele was carried in one each of the 576 (0.2%) control subjects and the 90 (1.1%) AAD subjects as a heterozygote (P = 0.254, not significant), suggesting that this common AIRE-1 gene abnormality does not have a major role in sporadic (non-APS1) AAD.

Identification of epitopes on tyrosinase which are recognized by autoantibodies from patients with vitiligo

The identification of tyrosinase autoantibodies in some patients with vitiligo has previously been reported. In this study we have determined the B cell epitopes on tyrosinase which are recognized by these autoantibodies. Deletion derivatives of tyrosinase cDNA were constructed and then translated in vitro with the concomitant incorporation of [35S]methionine into the protein products. The 35S-labeled tyrosinase derivatives were subsequently used in radioimmunoassays to investigate the reactivity of sera from five vitiligo patients. The epitope regions identified were: three in a central region of tyrosinase (amino acids 240-255, 289-294, and 295-300) and two others towards the C-terminal end of the protein (amino acids 435-447 and 461-479). Computer analysis of the potential B cell epitopes on tyrosinase revealed that the epitope regions recognized by the vitiligo sera were located in areas predicted to be highly antigenic. In addition, the centrally located antigenic regions (amino acids 289-294 and 295-300) had amino acid sequence homology to both tyrosinase-related protein-1 and -2. Thus, the epitopes on tyrosinase recognized by vitiligo patient sera are heterogeneous and include a region with homology to two related proteins which may explain the cross-reactivity previously noted between these antigens.

Analysis of a microsatellite polymorphism of the cytotoxic T-lymphocyte antigen-4 gene in patients with vitiligo

The CTLA-4 gene encodes a T-cell receptor that is involved in the regulation of T-cell activation. Recent studies have demonstrated an association of a microsatellite polymorphism [variant lengths of a dinucleotide (AT)n repeat] lying in exon 3 of the CTLA-4 gene, specifically a 106-bp allele, with autoimmune disorders, such as Graves' disease, autoimmune Addison's disease and autoimmune hypothyroidism. The aim of the present study was to determine whether the same polymorphism of the CTLA-4 gene was associated with vitiligo, a disorder that may have an autoimmune origin and can be present in patients who have one or more autoimmune diseases. CTLA-4 gene microsatellite polymorphisms were determined for 74 vitiligo patients (53 without any autoimmune disorder; 21 with one or more autoimmune disease) and 173 healthy controls, who had no clinical evidence of either vitiligo or any other autoimmune disorder, by polymerase chain reaction amplification of genomic DNA and resolution of the products on polyacrylamide sequencing gels. The frequency of the 106-bp allele was significantly increased (chi2 = 5. 2; P = 0.02) in vitiligo patients as a whole, in comparison with control subjects. However, when the patients were classified according to the absence or presence of an autoimmune disorder, the frequency of the 106-bp allele was significantly increased (chi2 = 14.8; P = 0.0001) only in the group of vitiligo patients who also had an autoimmune disease. However, the fact that 17 of 21 patients also had either autoimmune thyroiditis or autoimmune Addison's disease probably accounts for the apparent association of vitiligo and the 106-bp allele in this patient group. However, it was found that the relative risk of 3.2, conferred by the 106-bp allele in this group of vitiligo patients, was greater than that found for patients with only either Graves' disease, autoimmune hypothyroidism or autoimmune Addison's disease, with values of 2.1, 2.2 and 2.2, respectively. For the group of patients without an autoimmune disorder, there was no significant difference (chi2 = 0.2; P = 0.64) in the frequency of the 106-bp allele when compared with control subjects. These results indicate that there is no association between the 106-bp allele and vitiligo, at least when the disorder occurs in the absence of an autoimmune disease.

Autoantibodies to human melanocyte-specific protein pmel17 in the sera of vitiligo patients: a sensitive and quantitative radioimmunoassay (RIA)

In the present study we describe the in vitro transcription-translation of human melanocyte-specific protein Pmel17 cDNA and subsequent use of the resulting 35S-labelled Pmel17 in an RIA to analyse vitiligo sera for the presence of Pmel17 antibodies. Of 53 vitiligo sera examined in the assay, three (5.9%) were found to be positive for Pmel17 antibodies. In contrast, sera from 20 healthy controls, 10 patients with Hashimoto's thyroiditis and 10 patients with Graves' disease (GD) were all negative for Pmel17 antibodies. All three patients positive for Pmel17 antibodies (aged 50-63 years) had had vitiligo of the symmetrical type for > 1 year and all of them also had an associated autoimmune disorder: GD in one and autoimmune hypothyroidism in two. In addition, all three patients had antibodies to the melanogenic enzymes tyrosinase, tyrosinase-related protein-1 (TRP-1) and tyrosinase-related protein-2 (TRP-2) in their serum. Absorption studies indicated that preincubation with COS-7 cell extract containing expressed Pmel17 absorbed out the immunoreactivity of the three sera positive in the RIA, confirming the anti-Pmel17 reactivity of the sera from these patients. In contrast, COS-7 cell extracts containing either expressed tyrosinase, TRP-1 or TRP-2 did not remove the anti-Pmel17 reactivity of the three sera in the RIA. This lack of cross-reactivity suggests that the humoral response to Pmel17 in these patients is specific and independent of the antibody reactivity to tyrosinase, TRP-1 and TRP-2.

A cytotoxic T lymphocyte antigen-4 (CTLA-4) gene polymorphism is associated with autoimmune Addison's disease in English patients

OBJECTIVE

Recent studies have demonstrated an association between a microsatellite polymorphism of the CTLA-4 gene, specifically a 106 base pair allele, and both Graves' disease and autoimmune hypothyroidism. The aim of the present study was to determine whether the same polymorphism of the CTLA-4 gene was associated with autoimmune Addison's disease.

DESIGN AND PATIENTS

We analysed a microsatellite polymorphism (variant lengths of a dinucleotide (AT)n repeat) within exon 3 of the CTLA-4 gene in the following groups: 21 English patients with non-associated Addison's disease, 18 with autoimmune polyglandular syndrome type 2 (APS2) and 173 healthy control subjects; 26 Norwegian patients with non-associated Addison's disease, 9 with autoimmune polyglandular syndrome type 1 (APS1), 17 with APS2 and 100 controls; 3 Finnish patients with non-associated Addison's disease, 5 with APS2 and 71 controls; 10 Estonian patients with non-associated Addison's disease, 2 with APS2 and 45 controls.

MEASUREMENTS

The CTLA-4 microsatellite gene polymorphisms were determined by polymerase chain reaction amplification of genomic DNA and resolution of the products on sequencing gels.

RESULTS

The frequency of the 106 base pair allele was significantly increased in the groups of English patients with either non-associated Addison's disease or APS2 (P = 0.02 and 0.04, respectively), when compared to healthy controls with no clinical evidence or family history of either Addison's disease or any other autoimmune disorder. For Norwegian patients with either non-associated Addison's disease, APS1 or APS2, there was no association (P = 0.69, 0.62 and 0.97, respectively). This was also the case for Finnish patients with either non-associated Addison's disease or APS2 (P = 0.23 and 0.28, respectively) and for Estonian patients with either non-associated Addison's disease or APS2 (P = 0.34 and 0.29, respectively).

CONCLUSIONS

These results indicate that differences exist in the frequency of the 106 base pair allele in different population groups and in only the English population was the 106 base pair allele associated with Addison's disease.

Autoantibodies to tyrosinase-related protein-1 detected in the sera of vitiligo patients using a quantitative radiobinding assay

In the present study, we describe the in vitro transcription-translation of human tyrosinase-related protein-1 (TRP-1) cDNA and subsequent use of the resulting 35S-labelled TRP-1 in a radioimmunoassay to analyse vitiligo sera for the presence of TRP-1 antibodies. Of 53 vitiligo sera examined in the assay, three (5.7%) were found to be positive for TRP-1 antibodies. In contrast, sera from 20 controls, 10 patients with Hashimoto's thyroiditis and 10 patients with Graves' disease were all negative for TRP-1 antibodies. Although glycosylation of the labelled protein was necessary for its immunoprecipitation by TRP-1-specific monoclonal antibody TA99, this post-translational processing did not affect the binding of any of the sera tested. All three patients positive for TRP-1 antibodies (aged 50-63 years) had had vitiligo of the symmetrical type for more than 1 year, and all of them also had an associated autoimmune disorder: Graves' disease in one and autoimmune hypothyroidism in two. In addition, antibodies to the melanogenic enzymes tyrosinase and tyrosinase-related protein-2 (TRP-2) were present in their serum. Absorption studies indicated that preincubation with COS-7 cell extract containing either expressed TRP-1, tyrosinase or TRP-2 absorbed out the immunoreactivity of the three sera positive in the radioimmunoassay (RIA) with [35S]TRP-1. The results indicate that autoantibodies to TRP-1 cross-react with tyrosinase and TRP-2, suggesting one or more common epitopes between the three proteins.

Analysis of immunoglobulin G kappa antithyroid peroxidase antibodies from different tissues in Hashimoto's thyroiditis

Antibodies (Ab) to thyroid peroxidase (TPO) are common in patients with autoimmune thyroid disease and may play a role in disease pathogenesis. We have prepared immunoglobulin G kappa (IgG kappa) and IgG lambda phage display combinatorial libraries from the cervical (thyroid-draining) lymph nodes of 2 Hashimoto's thyroiditis patients and from the thyroid of 1 patient. After selection with purified recombinant human TPO, up to 10 high affinity IgG kappa clones from each tissue source were analyzed further. No IgG lambda Fab were detected in the patient with the highest TPO Ab titer. Sequence analysis of the clones showed restricted heavy and light chain usage, similar to that in previously published TPO-reactive Fabs. This was despite the substantially larger sizes of the initial libraries, the use of lymph node tissue to generate libraries, and the analysis of the repertoire in patients with Hashimoto's thyroiditis rather than Graves' disease. There was overall similarity in sequences obtained from lymph node and thyroid libraries, with higher levels of somatic hypermutation in the former. The Fab inhibited binding of serum TPO Ab from five patients by 55-95%. These data together with those from previous reports indicate that although there is no unique Ab gene usage, there is the recurrent presence of certain variable regions in the high affinity TPO Ab response.

Immunoprecipitation of melanogenic enzyme autoantigens with vitiligo sera: evidence for cross-reactive autoantibodies to tyrosinase and tyrosinase-related protein-2 (TRP-2)

In the present study we describe the detection of TRP-2 antibodies in vitiligo patients using in vitro 35S-labelled human TRP-2 in a radioimmunoassay. Of 53 vitiligo sera examined in the assay, three (5 9%) were found to be positive for TRP-2 antibodies. In contrast, 20 control sera, sera from 10 patients with Hashimoto's thyroiditis and sera from 10 patients with Graves' disease were all negative. All three patients positive for TRP-2 antibodies (mean age 54 years, age range 50-63 years) had had vitiligo of the symmetrical type for more than 1 year and all of them also had an associated autoimmune disorder: Graves' disease in one and autoimmune hypothyroidism in two. In addition, antibodies to the melanogenic enzyme tyrosinase were present in their serum. To examine any immunological cross-reactivity between TRP-2 and tyrosinase, the three vitiligo sera positive for TRP-2 antibodies were preabsorbed with COS-7 cell extract containing either expressed TRP-2 or tyrosinase, and subsequently used in the radioimmunoassay. These absorption studies indicated that preincubation with both proteins inhibited the immunoreactivity of the positive sera in the immunoassay using in vitro translated 35S-TRP-2. This antibody cross-reactivity suggests the humoral response to the two melanogenic enzymes in these patients may not be entirely independent.

Immunoglobulin G kappa antithyroid peroxidase antibodies in Hashimoto's thyroiditis: epitope-mapping analysis

Patients with autoimmune thyroid disease frequently have high affinity antibodies to thyroid peroxidase (TPO), although the role they play in disease pathogenesis is not known. We have previously prepared 37 monoclonal anti-TPO IgG kappa Fab fragments from two patients with Hashimoto's thyroiditis and demonstrated the similarity of these Fab sequences to those published previously, mainly derived from patients with Graves' disease. In this paper, we described epitope mapping of these Fabs using a previously characterized panel of murine monoclonal antibody (mAb) and show that the Fabs bind to two neighboring epitopes on native TPO. Although the epitope-mapping method differs from that used to characterize previously published TPO-reactive Fab sequences, it indicates a similarly restricted response to neighboring epitopes in both Graves' disease and Hashimoto's thyroiditis. The epitope mapping included mAb 47, which binds to a linear TPO peptide of known sequence in addition to native TPO. Although TPO-reactive Fab did not inhibit the binding of mAb 47, mAb 47 did inhibit the binding of Fab, indicating the likely site of the immunodominant region on native TPO. These results confirm the restricted nature of TPO antibody and further delineate the immunodominant region of native TPO as defined by the mAb.

Detection of tyrosinase autoantibodies in patients with vitiligo using 35S-labeled recombinant human tyrosinase in a radioimmunoassay

Tyrosinase antibodies recently have been reported to occur frequently in patients with vitiligo. We describe the detection of tyrosinase antibodies in vitiligo patients using in vitro 35S-labeled human tyrosinase in a radioimmunoassay. Of 46 vitiligo sera examined in the assay, five (10.9%) were found to be positive for tyrosinase antibodies. In contrast, 20 control sera and sera from 10 patients with Hashimoto's thyroiditis were negative. Four of the sera positive in the radioimmunoassay were also positive in an ELISA using mushroom tyrosinase as antigen. Absorption studies indicated that pre-incubation with mushroom tyrosinase absorbed out the immunoreactivity of the positive sera in the radioimmunoassay, suggesting cross-reactivity, but this absorption was never complete, indicating that there are tyrosinase antibodies in human sera that do not react with the mushroom protein. There was no obvious association between the presence of tyrosinase antibodies and the age of the patients (range: 22-62 y), their duration of disease (range: 5-20 y), or the type of vitiligo (one segmental, one symmetrical/periorificial, three symmetrical), although the three patients with the highest antibody levels also had an associated autoimmune disorder (one with Graves' disease; two with autoimmune hypothyroidism). The results confirm that tyrosinase autoantibodies are present in the sera of vitiligo patients but at a low frequency. The technique described is sensitive and quantitative and allows the detection of conformational epitopes. It will be useful in longitudinal studies to determine the relation between the clinical features of vitiligo and tyrosinase antibody levels.

Cloning and analysis of IgG kappa and IgG lambda anti-thyroglobulin autoantibodies from a patient with Hashimoto's thyroiditis: evidence for in vivo antigen-driven repertoire selection

Antibodies to thyroglobulin (Tg) are commonly found in patients with the autoimmune thyroid diseases Graves' disease and Hashimoto's thyroiditis as well as in individuals with apparently normal thyroid function. Although it is not clear how Tg Abs are involved in the pathology of the diseases, the study and analysis of these Abs may nevertheless be instructive in allowing the development of an Ab response to an autoimmune disease-associated self Ag to be followed. We have prepared IgG kappa and lambda phage display combinatorial libraries from the cervical lymph node of a single Hashimoto's thyroiditis patient with a high anti-Tg titer. These were selected with purified human Tg, and 10 IgG kappa and 9 IgG lambda clones were analyzed further. Sequence analysis of the clones showed a very highly restricted heavy chain usage and a less restricted light chain usage. There was a variable degree of divergence from germ-line sequence in the light chain sequences, with a clear relationship between relatively higher affinity of the Fab for human Tg and an increased degree of somatic hypermutation. The Tg-selected Fab did not bind to Tg from other species, to reduced denatured Tg, or to thyroid peroxidase. The Fab inhibited patient serum binding to human Tg by between 39 and 79%. In summary, we have isolated 19 high affinity, human Tg-specific Fab and shown that the relative affinity of the Fab is directly related to the pattern of somatic hypermutation.

Cloning and analysis of IgG kappa and IgG lambda anti-thyroglobulin autoantibodies from a patient with Hashimoto's thyroiditis: evidence for in vivo antigen-driven repertoire selection

Antibodies to thyroglobulin (Tg) are commonly found in patients with the autoimmune thyroid diseases Graves' disease and Hashimoto's thyroiditis as well as in individuals with apparently normal thyroid function. Although it is not clear how Tg Abs are involved in the pathology of the diseases, the study and analysis of these Abs may nevertheless be instructive in allowing the development of an Ab response to an autoimmune disease-associated self Ag to be followed. We have prepared IgG kappa and lambda phage display combinatorial libraries from the cervical lymph node of a single Hashimoto's thyroiditis patient with a high anti-Tg titer. These were selected with purified human Tg, and 10 IgG kappa and 9 IgG lambda clones were analyzed further. Sequence analysis of the clones showed a very highly restricted heavy chain usage and a less restricted light chain usage. There was a variable degree of divergence from germ-line sequence in the light chain sequences, with a clear relationship between relatively higher affinity of the Fab for human Tg and an increased degree of somatic hypermutation. The Tg-selected Fab did not bind to Tg from other species, to reduced denatured Tg, or to thyroid peroxidase. The Fab inhibited patient serum binding to human Tg by between 39 and 79%. In summary, we have isolated 19 high affinity, human Tg-specific Fab and shown that the relative affinity of the Fab is directly related to the pattern of somatic hypermutation.

Analysis of transcriptional control of the gerD spore germination gene of Bacillus subtilis 168

The gerD locus of Bacillus subtilis comprises a single gene whose function is essential for the germination of B. subtilis spores in media containing asparagine, glucose, and fructose. The expression of gerD has been characterized by using a chromosomal lacZ fusion to the gerD promoter. The promoter is switched on at the same time as the synthesis of glucose dehydrogenase, 2.5 h after sporulation has been initiated in the developing forespore. The gerD gene is not expressed in spoIIB or spoIIIA, -IIIB, -EIII, -FIII, or -IIIG mutants, but it is expressed in spoIIIC and -IIID and spoIVA mutant backgrounds. The in vivo transcriptional start point of the gene has been mapped by primer extension analysis, and sequences upstream from the start point show considerable homology with the promoter consensus sequences recognized by RNA polymerase containing the forespore-specific sigma factor sigma G (E sigma G). gerD is transcribed in vitro by E sigma G with a similar if not identical start point to that found in vivo, and expression of the gene can be rapidly induced in vegetative cells following the induction of sigma G synthesis. These results indicate that gerD is another member of the sigma G regulon, which includes a number of genes expressed only in the forespore compartment of sporulating cells of B. subtilis.