Recognition by recombinant autoimmune thyroid disease-derived Fab fragments of a dominant conformational epitope on human thyroid peroxidase

To characterize the nature of thyroid peroxidase (TPO) autoantibodies present in the sera of patients with autoimmune thyroid disease, we cloned three IgG1/kappa Fab fragments which bind 125I-TPO. This was accomplished by the molecular cloning and expression in bacteria of IgG gene fragments from B cells infiltrating the thyroid of a patient with Graves' disease. The three Fab fragments (SP2, SP4, and SP5) are coded for by a common heavy chain (VH1, D, JH3) and three related, but different, light chains (VK1, JK2). The SP Fab fragments bind specifically to TPO with high affinities (6 x 10(-11)-2 x 10(-10) M) comparable to those of serum TPO autoantibodies. TPO autoantibodies represented by the SP Fab fragments are present in all 11 patients studied, constitute a high proportion (36-72%) of serum TPO autoantibodies in individual patients and interact with a conformational epitope on TPO.

Surrogate thyroglobulin receptors and T cell proliferation in Hashimoto's thyroiditis

Immunoglobulin molecules on the surface of a B lymphocyte are the endogenous "receptors" to which specific antigens bind. Studies in mice have shown that a monoclonal antibody, conjugated with palmitate to provide a lipid tail, can be inserted into the cell membrane to provide a "surrogate" antigen receptor. We have investigated whether a palmitate conjugate of a human monoclonal antibody specific for thyroglobulin (TG) could function as a surrogate TG receptor on blood mononuclear cells separated into fractions enriched for T cells or depleted of T cells (non-T cells). Using flow cytometry, we detected surrogate TG receptors on non-T (but not on T) cells from 11 of 11 individuals studied (5 Hashimoto patients and 6 control donors). In contrast, endogenous TG receptors could only be detected on non-T cells from 1 of 3 Hashimoto patients and from 0 of 4 control donors. Because of the efficient binding of TG by surrogate receptors on non-T cells, we assessed the ability of such cells to present TG to T cells. Proliferation in response to TG was observed in T cells from only 1 of 5 Hashimoto patients. This low frequency of response was no different from that previously detected using cultures of T cells and autologous dendritic cells. Therefore, the successful generation of surrogate receptors on non-T cells is not associated with more efficient TG presentation of T cells. Furthermore, the significance of the present study is that the T cells, not the antigen-presenting cells, are likely to be the limiting element in the T cell proliferative response to TG and other thyroid autoantigens.

A human Fab fragment specific for thyroid peroxidase generated by cloning thyroid lymphocyte-derived immunoglobulin genes in a bacteriophage lambda library

A human Fab fragment (SP2) which binds specifically to human thyroid peroxidase has been generated by expressing random combinations of heavy and light chain immunoglobulin genes (derived from Graves' thyroid cDNA) in a bacteriophage lambda library. In common with many serum TPO autoantibodies, the cloned Fab fragment is IgG1 kappa and has a high affinity for TPO (approximately 10(-9) M). On the basis of their nucleotide sequences, the heavy and light chain genes coding for SP2 belong to families VHI, (D), JH3 and VKI, JK2, respectively. These data provide the first characterization at a molecular level of a human thyroid peroxidase antibody associated with autoimmune thyroid disease.

Severe combined immunodeficient (SCID) mice: a model for investigating human thyroid autoantibody synthesis

We have studied the ability of lymphocytes from the blood, thyroid and lymph nodes of patients with autoimmune thyroid disease (AITD) to produce autoantibodies to thyroglobulin (Tg) and/or thyroid peroxidase (TPO) in SCID mice. Human IgG class Tg and/or TPO antibodies were detectable in plasma from SCID mice 7 days after transfer of 15-25 x 10(6) cells/mouse and the highest levels were recorded 2-3 weeks later. In contrast, Tg and/or TPO antibodies were undetectable in recipients of lymphocytes from thyroid antibody negative controls. AITD thyroid lymphocytes produced the most antibody in recipient mice and lower levels were observed in recipients of AITD blood and lymph node lymphocytes. The amounts of Tg and/or TPO antibody detected were in accordance with the ability of thyroid and lymph node lymphocytes to secrete these autoantibodies spontaneously in culture (indicating the presence of cells activated in the patient) and with the capacity of blood lymphocytes (probably B memory cells) to secrete Tg and/or TPO antibodies in culture in response to pokeweed mitogen. Tg antibodies in plasma from SCID recipients of thyroid lymphocytes were of subclasses IgG1, IgG2 and IgG4 and the proportions closely resembled those of the donor's serum Tg antibodies. Blood lymphocytes transferred to SCID recipients were also able to produce Tg antibodies of subclasses 1, 2 and 4 but the subclass distribution varied between mice and the reason for this is not clear at present. Since SCID mice provide an environment in which B lymphocytes from patients with AITD can be activated without mitogen to secrete thyroid antibodies, this model will provide a powerful system for elucidating the mechanisms regulating the secretion of human antibodies to Tg and TPO.

Human monoclonal thyroglobulin autoantibodies of high affinity. I. Production, characterisation and interaction with murine monoclonal thyroglobulin antibodies

Four hybridomas secreting human thyroglobulin (Tg) autoantibodies of different IgG subclasses and light chain types (IgG1 lambda, IgG1 kappa, IgG2 lambda and IgG2 kappa) were obtained by direct fusion of Hashimoto thyroid lymphocytes with the mouse myeloma X63-Ag.653. The autoantibodies were specific for human Tg and the functional affinities were high (only 2.6-3.9 log10 pM Tg required to give 50% inhibition of binding in ELISA). Using thyroid lymphocytes, 4 lines secreting Tg autoantibodies were obtained from 11 fusions compared with 1 line from 32 fusions of Epstein Barr virus infected blood lymphocytes, which emphasises the importance of using lymphocytes derived from a tissue known to be enriched in thyroid autoantibody secreting precursor B cells. These 4 human Tg autoantibodies, as well as an IgG2 lambda Tg antibody previously derived from Hashimoto blood B cells and an IgG4 kappa monoclonal Tg antibody present in a Hashimoto serum, were used in attempts to probe the interaction between human Tg autoantibodies and the Tg molecule (2 polypeptides of 330 KD). The binding to 125-I Tg by 3/7 murine monoclonal antibodies was inhibited (36-78%) by an IgG2 lambda and an IgG4 kappa human monoclonal Tg autoantibody, indicating an overlap between the epitopes recognised by these 3 murine monoclonal Tg antibodies and 2 monoclonal human Tg autoantibodies. None of the human Tg autoantibodies (or the murine monoclonal Tg antibodies) bound to Tg denatured by reduction and alkylation. Although the number of observations is limited, our study demonstrates that high affinity human monoclonal Tg autoantibodies, like polyclonal serum Tg autoantibodies, recognise non-linear B cell epitopes on conformationally intact human Tg.

Human monoclonal thyroglobulin autoantibodies of high affinity. II. Interaction between thyroglobulin and thyroglobulin autoantibodies of different IgG subclasses

The interaction of human thyroglobulin (Tg) autoantibodies of different IgG subclasses with Tg was investigated using four high affinity human monoclonal thyroglobulin (Tg) autoantibodies, secreted by human-mouse hybridomas, of subclasses IgG1 (kappa and lambda) and IgG2 (kappa and lambda) and an IgG4 kappa serum monoclonal Tg antibody. With exception of a low level of interference in binding between one IgG1 lambda Tg antibody and one IgG2 kappa Tg antibody (27% decrease), binding by human monoclonal Tg antibodies of one IgG subclass was unaffected by pre-incubation of 125-I Tg (or Tg on an ELISA plate) with a human monoclonal Tg antibody of a different IgG subclass. Furthermore, preincubation of Tg-coated ELISA plates with an IgG1 human monoclonal Tg antibody had little effect on binding to Tg by IgG2, IgG3 and IgG4 Tg antibodies present in the sera of 6 Hashimoto patients. Comparable observations were made using an IgG2 monoclonal Tg antibody and serum Tg antibodies of subclasses IgG1, IgG3 and IgG4. Binding of an IgG1 kappa Tg antibody was inhibited (> 80%) by pre-incubation of Tg with an IgG1 lambda Tg antibody derived by fusion of lymphocytes from the same Hashimoto patient. In contrast, pre-incubation of Tg with an IgG2 kappa Tg antibody had little effect on subsequent binding by an IgG2 lambda Tg antibody derived from lymphocytes of a different Hashimoto patient.(ABSTRACT TRUNCATED AT 250 WORDS)

Geographical distribution of subclinical autoimmune thyroid disease in Britain: a study using highly sensitive direct assays for autoantibodies to thyroglobulin and thyroid peroxidase

In order to determine whether the geographical distribution of autoimmune thyroid disease in Britain is influenced by the pattern of iodine intake, the prevalence of subclinical disease (detectable antithyroid antibodies in biochemically euthyroid individuals) has been measured in female blood donors from seven towns in England and Wales previously characterised in terms of past and present iodine intake. Thyroglobulin antibody and thyroid peroxidase antibody were measured by highly sensitive assays which are based on the direct interaction between antibody and radiolabelled antigen. Excluding cases of overt thyroid disease (biochemically hypo- or hyperthyroid with thyroid antibodies), the overall prevalences of the antibodies in sera from the 698 female blood donors were 17.8% for thyroglobulin antibody and 17.8% for thyroid peroxidase antibody. Both antibodies were found in 12.3% of the female blood donors. In contrast, the prevalences of thyroglobulin antibody and thyroid peroxidase antibody were 41 and 43%, respectively, in the 117 female relatives of 18 probands with autoimmune thyroid disease, but the highest prevalences were observed in groups of women patients with Graves' disease (N = 39) or Hashimoto's disease (N = 39) (51, and 97% for thyroglobulin antibody, respectively, and 72 and 97% for thyroid peroxidase antibody, respectively). Antibody prevalence increased with age in the female blood donors rising from 10.6% at age 18-24 to 30.3% at age 55-64 for thyroglobulin antibody and from 14.9% at age 18-24 to 24.2% at age 55-64 for thyroid peroxidase antibody. Geographical differences in the prevalences of both antibodies were not significant and did not correlate with either the previous goitre prevalence or with current differences in iodine intake.(ABSTRACT TRUNCATED AT 250 WORDS)

Thyroid autoantigens and human T cell responses

We investigated the ability of T cells from patients with Hashimoto's thyroiditis and with Graves' disease as well as control donors to proliferate in response to thyroid peroxidase (TPO) and thyroglobulin using (i) lymphoid cells from different lymphoid organs; (ii) unfractionated or CD8- depleted lymphoid suspensions or T cells + autologous low density cells (LDC); (iii) 200-microliters well cultures and 20-microliters hanging-drop microcultures; and (iv) intact TPO and thyroglobulin, denatured thyroglobulin and 12 synthetic peptides predicted on the basis of the amino acid sequence of TPO to be T cell epitopes. In 200-microliters well cultures, proliferative responses (assessed in terms of 3H-thymidine uptake) to intact TPO or thyroglobulin, digested thyroglobulin or synthetic TPO peptides were not significantly different in unfractionated or CD8-depleted lymphoid suspensions from blood, thyroid or lymph nodes of TPO/thyroglobulin autoantibody-positive patients, autoantibody-negative patients or control donors. In contrast, blood T cells from some high titre patients with Hashimoto's thyroiditis (but not from healthy individuals) proliferated in response to intact thyroglobulin or TPO presented by autologous LDC in hanging-drop microcultures. Heat denatured thyroglobulin (with which thyroglobulin autoantibodies do not interact) did not stimulate proliferation and this observation, together with the ability of T cells from some patients to respond to intact thyroglobulin in the absence of LDC, indicated that thyroglobulin-specific B cells may be involved in antigen presentation. As we were unable to demonstrate proliferation by blood T cells + LDC from all thyroglobulin antibody-positive patients with Hashimoto's thyroiditis, our studies suggest that the presence of sufficient precursor T cells, as well as the number and type of antigen-presenting cells, are critical for T cell proliferative responses to human TPO and thyroglobulin.

IgG antibody and delayed-type hypersensitivity responses in nude mice grafted with thymic epithelium

This study compared the ability of foetal thymic epithelium depleted of lymphocytes and dendritic cells, by low temperature or deoxyguanosine (dGuo) treatment in organ culture, to reconstitute T-cell function in nude mice. It is shown that renal capsule grafts of either type could promote the development of functional T lymphocytes in the periphery, as judged by in vivo assays. Both syngeneic and allogeneic thymic epithelium endowed nude mice with the capacity to mount IgG antibody and delayed-type hypersensitivity (DTH) responses to the T-dependent antigen ovalbumin (OVA). Functional reconstitution was accompanied by the appearance of Thy-1-bearing cells in the spleens of thymic grafted nude mice. The results from allogeneically grafted recipients show that a substantial population of peripheral T cells was present that collaborated with B cells and other antigen-presenting cells (APC) which do not express major histocompatibility complex (MHC) molecules of the thymus donor haplotype.

Cytokines, thyroid autoantibody synthesis and thyroid cell survival in culture

In autoimmune thyroid disease lymphoid cells infiltrating the thyroid gland occur in conspicuous aggregates or as a diffusely distributed population invading the thyroid follicles. Consequently cytokines secreted by activated T cells or macrophages could influence neighbouring thyroid cells as well as other lymphocytes. We have investigated this possibility using recombinant cytokines. Thyroid cell survival was assessed in terms of mitochondrial dehydrogenase activity in monolayers exposed to tumour necrosis factor-alpha (TNF-alpha), interferon-gamma (IFN-gamma), interleukin-1 (IL-1 alpha and beta) and interleukin-2 (IL-2) in the presence or absence of thyroid-stimulating hormone (TSH). Neither TNF-alpha nor IL-2 affected thyroid cell survival, IFN-gamma was usually inhibitory and IL-1 alpha slightly enhanced cell survival in some experiments. However, the effects were small and variable and were not enhanced by potentially synergistic combinations of cytokines, longer periods of exposure, or different culture conditions. In contrast, IFN-gamma, IL-2 and TNF-alpha inhibited the ability of thyroid lymphocytes from patients with Graves' disease and Hashimoto's thyroiditis to synthesize autoantibodies to thyroid peroxidase (TPO) and thyroglobulin (Tg). Comparison of lymphoid populations isolated by digestion and/or mechanical disaggregation indicated that a population of activated B cells, plasma cells and T cells, intimately associated with thyroid cells since they could only be extracted by digestion, was influenced by cytokines. Our studies suggest that in addition to its well-recognized ability to induce MHC class II antigens on thyroid cells, IFN-gamma may inhibit thyroid cell proliferation and TNF-alpha, IFN-gamma and IL-2 may down-regulate thyroid autoantibody synthesis.

Thyroid peroxidase and the induction of autoimmune thyroid disease

Animal models of autoimmune thyroid disease are associated with thyroglobulin (Tg) as autoantigen whereas in man the autoimmune response to microsomal antigen/thyroid peroxidase (TPO) appears to play a major role in thyroiditis. Consequently, we have compared the ability of TPO and Tg to induce thyroid autoantibodies and thyroid damage in mice known to be susceptible (CBA/J) or resistant (BALB/c) to thyroiditis induced using murine Tg. Groups of three to five mice were immunized twice using Freund's complete adjuvant with 80-100 micrograms highly purified porcine (p) TPO, pTg, rat (r) Tg, human Tg, bovine serum albumin (BSA) or BSA + 0.2 micrograms pTg (the level of Tg contamination of TPO). Four weeks after immunization with TPO, plasma from CBA/J (but not BALB/c) mice contained IgG class antibodies which bound to TPO-coated tubes in the presence or absence of excess Tg (and could therefore be clearly distinguished from Tg antibodies) but there was no evidence of thyroiditis in either strain of mice. In contrast, in CBA/J mice immunized with rTg and, to a lesser extent in mice that had received pTg, thyroid tissue was infiltrated with lymphoid cells and/or neutrophils and antibodies to pTg (but not pTPO) were present. Our observations demonstrate that induction of TPO antibody alone is insufficient to lead to thyroiditis in CBA/J mice. Further, these studies emphasize the complex interactions between MHC and different thyroid antigens in the processes leading to thyroid destruction.

Relationship between thyroid autoantibody spectrotype and IgG subclass

The relationship between spectrotype and IgG subclass of autoantibodies to thyroglobulin (Tg) and thyroid peroxidase (TPO) has been investigated using sera from Hashimoto and Graves' patients. Isoelectric focussing (IEF) was carried out in gels over the range pI 3.5-9.5 followed by transblotting to nitrocellulose and probing the filters using 125I-labelled TPO and Tg. As has been shown previously for Tg antibodies, TPO antibody focussed over different pI values in different patients but the spectrotypes for individuals were constant over 2-5 years. Further, the pI values for TPO and Tg autoantibodies appeared to be related to IgG subclass, for example IgG1 Tg antibodies tended to focus nearer the cathode (pI 8.0-9.5) than IgG4 antibodies (pI 6.5-8.5) while antibodies of subclasses IgG1 + 2 + 4 produced spectrotypes covering a broad pI range (5.7-9.5). Consequently, it seems likely that the characteristic spectrotypes described by others for Tg autoantibodies, and those we now report for TPO antibodies, reflect the IgG subclass "fingerprints" which we suggest may be a measure of the ability of an individual to respond to different epitopes on these two thyroid antigens.

Highly sensitive assays of autoantibodies to thyroglobulin and to thyroid peroxidase

These highly sensitive assays are based on the interaction between thyroid autoantibodies and 125I-labeled autoantigens. Serum samples are incubated with labeled thyroid peroxidase (TPO) or thyroglobulin (Tg) to allow the formation of antibody-labeled antigen complexes. The complexes are then precipitated by addition of solid-phase Protein A. In the presence of high concentrations of TPO antibody or Tg antibody, more than 50% of the respective labeled antigen was precipitated, whereas only 1-2% was precipitated in the absence of autoantibody. Interassay CVs were 3.2% and 5.7%, respectively, for the anti-TPO and anti-Tg assays. There was no cross-reactivity between Tg antibody and TPO antibody. Results correlated highly significantly with results from other assay systems based on antigen-coated cells or plastic supports, but the assays described here were considerably more sensitive. Scatchard analysis of the assay data provided information on the affinity and serum concentration of TPO autoantibodies (ka approximately 10(9) L/mol and concentrations up to 1 g/L) and Tg autoantibodies (ka approximately 4 x 10(10) L/mol and concentrations up to 1 g/L). Overall, these assays provide a sensitive, precise, and convenient system for measuring and investigating the properties of thyroid autoantibodies.

Highly sensitive assays of autoantibodies to thyroglobulin and to thyroid peroxidase

These highly sensitive assays are based on the interaction between thyroid autoantibodies and 125I-labeled autoantigens. Serum samples are incubated with labeled thyroid peroxidase (TPO) or thyroglobulin (Tg) to allow the formation of antibody-labeled antigen complexes. The complexes are then precipitated by addition of solid-phase Protein A. In the presence of high concentrations of TPO antibody or Tg antibody, more than 50% of the respective labeled antigen was precipitated, whereas only 1-2% was precipitated in the absence of autoantibody. Interassay CVs were 3.2% and 5.7%, respectively, for the anti-TPO and anti-Tg assays. There was no cross-reactivity between Tg antibody and TPO antibody. Results correlated highly significantly with results from other assay systems based on antigen-coated cells or plastic supports, but the assays described here were considerably more sensitive. Scatchard analysis of the assay data provided information on the affinity and serum concentration of TPO autoantibodies (ka approximately 10(9) L/mol and concentrations up to 1 g/L) and Tg autoantibodies (ka approximately 4 x 10(10) L/mol and concentrations up to 1 g/L). Overall, these assays provide a sensitive, precise, and convenient system for measuring and investigating the properties of thyroid autoantibodies.

Serial studies on the affinity and heterogeneity of human autoantibodies to thyroglobulin

The functional affinity and heterogeneity of autoantibodies to thyroglobulin (Tg) were measured by an IgG subclass-specific solid-phase competition ELISA in patients with autoimmune thyroid disease. High-affinity IgG1 and IgG4 antibodies formed the major anti-Tg response. Both titre and affinity of IgG3 and IgG2 anti-Tg were generally low but in some Hashimoto's disease patients high-affinity IgG2 anti-Tg were found and IgG2 anti-Tg, unlike those of other subclasses, showed very restricted heterogeneity. The affinity of IgG4 anti-Tg was similar in patients with thyroid disease and their clinically euthyroid (normal) relatives. In contrast, a progressive increase in IgG1 anti-Tg affinity was seen in clinically euthyroid individuals compared with their relatives with thyroid disease and high titred Hashimoto's disease patients, suggesting that either rising titres of high affinity IgG1 anti-Tg or affinity maturation of IgG1 anti-Tg may be indicative of impending hypothyroidism.

Human thyroglobulin autoantibodies of subclasses IgG2 and IgG4 bind to different epitopes on thyroglobulin

IgG autoantibodies to thyroglobulin (Tg) in the serum of patients with autoimmune thyroid disease only recognize a very limited number of epitopes, probably between four and six (Nye, Pontes De Carvalho & Roitt, 1980) on the large Tg molecule (660,000 MW), but attempts to characterize the epitopes have been unsuccessful so far (Male et al., 1985). The distribution of Tg autoantibodies between the IgG subclasses also tends to be restricted and individual patients possess characteristic 'fingerprints' of high affinity IgG1 and/or IgG4 Tg antibodies with smaller amounts of IgG2 Tg antibody (McLachlan et al., 1987, 1988). We have therefore investigated the possibility that Tg autoantibodies of different IgG subclasses interact with different epitopes on Tg.

Progression of autoimmune damage in primary biliary cirrhosis: an immunohistochemical study

Aberrant MHC Class II antigen expression and the nature of the infiltrating lymphoid cells were studied by immunohistochemical techniques in liver biopsies from 37 patients with Primary biliary cirrhosis (PBC) (11 histological stage I, 13 stage II-III, 13 stage IV) and 15 patients with chronic non autoimmune liver disease. Bile duct epithelial cells expressed HLA-DR, DP and DQ antigens in biopsies from patients with early (Stage I) PBC and less frequently in the late cirrhotic phases of the disease (Stage IV); these observations support the hypothesis that induction of Class II antigens on epithelial cells may be involved in initiating autoimmune responses towards bile duct components. The presence of cytotoxic/suppressor T cells around the bile ducts in Stage I suggests a role for cell mediated destruction of the ducts at this early stage. The nature of the chronic inflammatory cell infiltrate in the portal tracts, periportal areas and lobular parenchyma does not establish the mechanism(s) involved in disease progression. However, the lack of Class II antigen expression on hepatocytes is compatible with the hypothesis that hepatocellular damage is non-specific and may be secondary to the initial bile duct injury.

Evidence for a potential common T-cell epitope between human thyroid peroxidase and human thyroglobulin with implications for the pathogenesis of autoimmune thyroid disease

In order to explore the possibility that, in autoimmune thyroid disease, anti-thyroglobulin (Tg) and anti-thyroid peroxidase (TPO) antibodies arise concurrently because they share a common T-cell epitope, we performed a detailed comparative analysis of the cDNA nucleotide sequences corresponding to these two genes. We discovered an 8 amino acid region (Leu-Ser-Glu-Asp-Leu-Leu-Ser- Ile in human TPO) in which there were 6 identical and 2 conserved amino acid residues when compared with human Tg. This remarkably similar region is near the amino-terminus of human TPO (residues 119-126) and the carboxyl-terminus of human Tg (residues 2763-2770). A second feature of interest was that this region of homology conforms to the Rothbard algorithm for a T-cell epitope. Third, probing of the Swiss-protein data bank (10,008 proteins containing 2,952,765 amino acids) with the human TPO region revealed greater homology for human Tg than for any other eukaryotic protein. Two bacterial proteins (E. coli aminopeptidase N and stringent starvation protein) had higher homology scores from human TPO than did human Tg. Our findings provide circumstantial evidence that human TPO and human Tg, and possibly certain bacterial proteins, do indeed share common T-cell epitopes that may play a role in the pathogenesis of autoimmune thyroid disease.

A human-mouse hybridoma which secretes monoclonal thyroglobulin autoantibody with properties similar to those of the donor patient's serum autoantibody

Human monoclonal antibodies produced by Epstein Barr (EB) virus transformation and/or cell fusion are frequently IgM antibodies which tend to cross react with a range of antigens and often bear little relationship to the highly specific IgG antibodies associated with human autoimmune disease. By fusing EB virus transformed B lymphocytes from a Hashimoto patient with a mouse myeloma line and selecting for synthesis of IgG class thyroglobulin (Tg) antibody, we have developed a hybridoma (VB/5) secreting Tg antibody of IgG2 subclass and lambda light chain type which has the characteristics of a monoclonal antibody on isoelectric focussing. The antibody has a high affinity for human Tg and recognises Tg from other primates but not non-primate Tg. However, it does not react with human thyroid peroxidase or a panel of other autoantigens. In terms of affinity constant, functional affinity and affinity heterogeneity, the antibody closely resembles the IgG2 lambda Tg antibody present in the serum of the Hashimoto patient whose B lymphocytes were used to develop the hybridoma. In addition to providing a useful reference standard for Tg antibody IgG subclass assays, VB/5 antibody and the hybridoma line provide a valuable starting point for detailed studies of Tg autoantibodies and the genes coding for the variable regions of their heavy and light chains.

HLA class II DNA genotypes in Graves' disease: clues to inheritance of the HLA-linked component of susceptibility

Restriction fragment length polymorphism analysis using DQ alpha, DQ beta and DR beta cDNA probes was performed in Graves' disease patients and control subjects. The following restriction fragment patterns were increased in frequency in patients compared with control subjects: 10 + 7.0 + 4.0kb DR beta/TaqI fragments (66% vs 32%; P less than 0.01; corrected P less than 0.06), 7.0 + 4.0kb DQ beta/BamHI fragments (55% vs 15%; P less than 0.001; corrected P less than 0.006), and a DQ alpha/TaqI 4.6kb fragment (75% vs 36%; P less than 0.005; corrected P less than 0.02). These associations could be accounted for by the known association of the B8-DR3 haplotype with the disorder. No non-DR3-related restriction fragment pattern was associated with the disease using any of the probes with restriction enzymes TaqI and BamHI. The 10 + 7.0 + 4.0kb DR beta/TaqI restriction pattern was identified in 23 of 35 Graves' disease patients. All 23 subjects were heterozygous for this pattern. This was inconsistent with simple recessive inheritance of the DR3-associated component of disease susceptibility (P = 0.01). The implications of these findings are discussed with reference to models for the inheritance of the HLA-linked component of Graves' disease susceptibility.

Autoantibodies to the thyrotropin receptor

This review considers recent developments in our understanding of the properties of TRAb, particularly measurement of the antibodies and their sites of action and synthesis. Two new assay methods have allowed considerable improvements in the sensitivity, specificity, precision, and ease of measuring TRAb. In particular: 1) receptor assays based on inhibition of receptor-purified labeled TSH binding to detergent-solubilized TSH receptors and 2) bioassays based on stimulation of cAMP release from monolayer cultures of isolated thyroid cells. Detailed studies with the two assays indicate that TSH receptor antibodies nearly always act as TSH agonists in patients with a history of Graves' hyperthyroidism. Studies in areas of dietary iodine sufficiency suggest that measurement of the antibodies at various stages in the course of treating Graves' disease can be of value in predicting the outcome of therapy. However, in areas of iodine deficiency, difficulties in the ability of patients' thyroid tissue to recover from the effects of antithyroid drugs may prevent the receptor antibodies from causing a relapse of thyrotoxicosis. Consequently, the predictive value of receptor antibody measurements would be expected to be lower in these geographical areas. Although patients with a history of Graves' hyperthyroidism nearly always have TRAb which act as TSH agonists, about 20% of patients with frank hypothyroidism due to autoimmune destruction of the thyroid have TRAb which act as TSH antagonists (blocking antibodies). There is some evidence that these blocking antibodies can cause hypothyroidism particularly in the neonate. With regard to the site of synthesis of TRAb, there is now direct evidence that they are synthesized by thyroid lymphocytes, particularly the lymphocytes in close proximity to thyroid follicular cells. This is consistent with the well established effects of antithyroid treatment (drugs, radioiodine, or surgery) on TRAb levels in addition to their effects on thyroid hormone synthesis. Recent studies using affinity labeling with 125I-labeled TSH have enabled elucidation of the structure of the TSH receptor. TSH receptors in human, porcine, and guinea pig thyroid tissue have a two-chain structure in which the TSH binding site is formed on the outside surface of the cell membrane by a water-soluble A subunit (Mr approximately 50 K). The A subunit is linked by a disulfide bridge and weak noncovalent bonds to the amphiphilic B subunit (Mr approximately 30 K). This subunit, which penetrates the lipid bilayer, probably forms the site for interaction of the receptor with the regulatory subunits of adenylate cyclase.(ABSTRACT TRUNCATED AT 400 WORDS)

T cell regulation of thyroglobulin autoantibody IgG subclasses in Hashimoto's thyroiditis

Microsomal and thyroglobulin (Tg) antibodies in patients with autoimmune thyroid disease are usually predominantly of subclasses IgG1 and/or IgG4 and the distribution pattern is characteristic for the serum of an individual. We have studied the role of T cells in synthesis of total IgG and Tg antibody IgG subclasses (measured by ELISA) in cultures of peripheral blood lymphocytes (PBL) from Hashimoto patients. Unfractionated PBL incubated with the T dependent activator pokeweed mitogen (PWM) synthesized IgG of all four IgG subclasses in the proportions 69% IgG1, 20% IgG2, 8% IgG3 and 3% IgG4; these values are similar to the proportions of the subclasses in serum. In contrast, the IgG subclass of Tg antibody was predominantly IgG1 in one patient, approximately equal proportions of IgG1 and IgG4 in four patients, and almost completely restricted to IgG4 in one patient; these patterns were similar to the subclass distribution of the autoantibodies in the individual patients' serum. B cells incubated alone secreted little Tg antibody but the response could be restored to the original levels and proportions of IgG1 and/or IgG4 Tg antibody by the addition of T cells either from the same individual or from another donor. Further, removal of suppressor T cells had little effect on the proportions of IgG1 and IgG4 Tg antibody although the total amounts of Tg antibody of both subclasses were sometimes increased. Our studies indicate that T cells are required in this in vitro system to elicit Tg antibody synthesis and to control the magnitude of the antibody response. However, the characteristic IgG subclass distribution of Tg antibody in an individual is determined at the level of the B cell.

The thyroid microenvironment in autoimmune thyroid disease: effects of TSH and lymphokines on thyroid lymphocytes and thyroid cells

Thyroid lymphocytes synthesize thyroid autoantibodies in close proximity to thyroid cells and consequently soluble mediators such as TSH and interleukins (IL) 1 and 2 may have unforeseen effects on lymphocytes and thyrocytes, respectively. Investigations of thyroid autoantibody synthesis by thyroid lymphocytes in vitro showed that TSH did not affect microsomal (Mic) antibody production, but thyroglobulin (Tg) antibody synthesis was decreased, probably as a result of complexing between Tg antibody and Tg secreted by small numbers of thyrocytes in the cell suspension. IL-1 and IL-2 partially mimicked the inhibitory effects on spontaneous autoantibody synthesis induced by Pokeweed mitogen (PWM) in cultures of thyroid lymphocytes. This inhibition may require a number of soluble mediators released by T cells in response to the mitogen; however, depletion studies indicated that the cell type responsible for PWM inhibition is unlikely to be a suppressor T cell and may be an NK cell. IL-1 and IL-2 had little effect on the viability of thyrocyte monolayers in an 18 h assay, but antibody dependent cells cytotoxicity (ADCC) using blood lymphocytes and thyroid autoantibody positive sera was demonstrated; further, the cytotoxicity appeared to be due to Mic antibodies. It is possible that IL-1 and/or IL-2 (as well as other cytokines) may affect thyroid cells after longer periods of exposure, either by altering them functionally or by direct damage. However, assuming that NK cells are present in sufficient numbers in the gland, ADCC could play a major role in the development of hypothyroidism in Hashimoto's disease.

The TSH receptor: structure and interaction with autoantibodies in thyroid disease

Studies of the TSH receptor using affinity labelling with photoactive derivatives of TSH and analysis by SDS-PAGE have shown that the receptor contains 2 subunits (A and B), linked by a disulphide bridge. Similar results are obtained with TSH receptors from human, porcine and guinea pig thyroid tissue and from guinea pig fat. Analysis of affinity labelled receptors under non-denaturing conditions suggest that subunits additional to the A and B subunits are not present. Hydrodynamic measurements indicate that the receptor A subunit has an approximately spherical structure (Stokes' radius 70 A) and when this interacts with TSH (an elongated structure with Stokes' radius 56A) a very elongated complex (Stokes' radius 104A) is formed. Isoelectric focusing studies of the TSH receptor A subunit, TSH and TSH receptor antibodies indicate that charge-charge interactions are of considerable importance in the binding of hormone and antibody to the receptor.

IgG subclass distribution of thyroid autoantibodies: a 'fingerprint' of an individual's response to thyroglobulin and thyroid microsomal antigen

The IgG subclass distribution of autoantibodies to thyroglobulin and thyroid microsomal antigen was studied in 21 patients with Graves' disease during fluctuations in total IgG class autoantibody levels induced by various forms of therapy. In addition, changes in autoantibody subclass distributions were investigated during the natural course of Hashimoto's disease in seven patients taking thyroxine. The autoantibodies were principally of subclasses IgG1 and/or IgG4 in Graves' patients although IgG2 contributed significantly to thyroglobulin antibodies in 5/7 Hashimoto sera. In Graves' disease the distribution of microsomal and thyroglobulin antibodies among the IgG subclasses remained essentially unchanged over periods of 6 months-2 years whether autoantibody levels decreased during carbimazole therapy or increased transiently following 131Iodine treatment or subtotal thyroidectomy. Similar observations were made for thyroglobulin antibodies in Hashimoto patients studied over 2 1/2-4 years; furthermore, the IgG subclass distribution of microsomal antibodies was usually different from that of thyroglobulin antibodies in the same patient. These observations suggest that the microsomal and/or thyroglobulin antibody subclass distribution is characteristic for a particular individual and may be regarded as the 'fingerprint' of an individual's response to these thyroid autoantigens.

Defective in vitro immunoglobulin production in response to pokeweed mitogen in patients with Hodgkin's disease pretreatment and in remission

In vitro production of IgG and IgM from peripheral blood lymphocytes and B-cell enriched fractions was assessed in a group of Hodgkin's disease (HD) patients and normal controls using pokeweed mitogen (PWM) stimulation. Our studies demonstrated a significant (P less than 0.01) reduction in the absolute number of helper (OKT4 positive) T cells and a significant alteration in the helper/suppressor T-cell ratio (0.89 +/- 0.15) compared to normal (1.83 +/- 0.31). Results from PWM stimulation experiments demonstrated that HD patients produced significantly lower IgG (P less than 0.01) and IgM (P less than 0.01) levels than controls. Synthesis of IgM but not IgG induced by PWM was subnormal after addition to patient B-cell cultures of autologous irradiated T cells or allogeneic irradiated normal T lymphocytes. Irradiated T cells from HD patients were as effective as normal T cells in helping PWM induced IgG and IgM synthesis by normal B cells. Our results suggest that in HD impaired circulating B-cell function is partly due to T-suppressor cell activity and furthermore that B-cell subpopulations producing different immunoglobulin isotypes may either be defective or vary in their susceptibility to T-cell suppression.

Subpopulations of thyroid autoantibody secreting lymphocytes in Graves' and Hashimoto thyroid glands

Lymphocytes isolated from Graves' and Hashimoto thyroid tissue by enzymatic (dispase) digestion or mechanical disaggregation were markedly different in terms of their ability to synthesize thyroid autoantibodies in culture. Dispase digestion, followed by removal of thyroid follicular cells, gave a lymphocyte population with a high T:B cell ratio (6:1). However, the ability of these cell suspensions to synthesize microsomal (Mic) and thyroglobulin (Tg) antibodies spontaneously was significantly increased compared with lymphoid suspensions isolated by mechanical means. Spontaneous synthesis of thyroid autoantibodies was not markedly enhanced in cell suspensions prepared from patients' lymph node tissue by digestion compared with mechanical disaggregation. Further, Mic and Tg antibody production by thyroid lymphocytes prepared using dispase was inhibited by pokeweed mitogen (PWM) whereas in most cases suspensions prepared from the same tissues by mechanical dispersion synthesized low or undetectable levels of autoantibodies whether PWM was present or absent. Digestion of tissue debris remaining after mechanical removal of lymphocytes gave suspensions which had an increased proportion of suppressor/cytotoxic T cells compared with suspensions produced mechanically or by digestion alone; however, in terms of spontaneous autoantibody synthesis and PWM induced inhibition, these suspensions were similar to these obtained by digestion alone. It would therefore seem that enzymatic digestion of thyroid tissue resulted in the isolation of a lymphoid population which was different from that extracted by mechanical disaggregation. The digestion process appears to permit the recovery of lymphocytes closely associated with thyroid follicular cells and our studies suggest that it is this population which makes the major contribution to autoantibody synthesis.

A technique for the isolation and mitogenic activation of thyroglobulin-specific human B lymphocytes

In previous studies we demonstrated that Hashimoto peripheral blood lymphocytes enriched for thyroglobulin (Tg) binding activity could be activated to secrete increased amounts of Tg antibody by Epstein - Barr virus (EBV) but not by pokeweed mitogen (PWM). We now report an investigation into the requirements for the isolation of Tg receptor positive (TgR+) B cells capable of being stimulated by PWM. The interaction between Hashimoto lymphocytes and Tg coated erythrocytes followed by red cell lysis interfered with the ability of the population to synthesize Tg antibody. However, this could be overcome if the rosettes formed between Tg coated erythrocytes and the Tg receptors on B cells were dissociated by digestion followed by red cell lysis and overnight incubation before the addition of PWM. Using this approach, Hashimoto TgR+ B cells could be stimulated by the mitogen to secrete immunoglobulin with a higher Tg antibody specific activity than unfractionated lymphocytes. Consequently, enriched populations of antigen specific human B cells capable of responding to mitogenic signals can be prepared by a positive selection technique.

TSH receptor antibody synthesis by thyroid lymphocytes

Several indirect observations have indicated that lymphocyte in the thyroid may be an important site of TSH receptor antibody synthesis in Graves' disease and we now describe an investigation of this possibility using improved lymphocyte isolation and TSH receptor antibody assay procedures. Our studies demonstrate that thyroid lymphocytes spontaneously produce TSH receptor antibody in culture. Furthermore, experiments with mitogen tend to suggest that these cells, in contrast to lymphocytes from lymph nodes draining the thyroid, are part of an active immune response to the TSH receptor.

Association between thyroid microsomal antibodies of subclass IgG-1 and hypothyroidism in autoimmune postpartum thyroiditis

The potential role of thyroid microsomal (Mic) antibodies in the development of postpartum hypothyroidism was investigated in 34 euthyroid women, whose sera were found to contain Mic antibodies in pregnancy. Additional serum samples were obtained 2. 5 and 10-12 months after delivery and analysed for IgG class and IgG subclass levels of Mic antibodies by ELISA techniques. Characteristically, Mic antibodies decreased from early pregnancy to 2 months postpartum, increased two-fold 5 months postpartum and had returned 10-12 months postpartum to the early pregnancy level. Mic antibodies were predominantly subclass IgG-1 or IgG-4 with only minor contributions from IgG-2 and IgG-3. In each individual the percentage contribution made by each IgG subclass to Mic antibody was essentially similar in early pregnancy and the postpartum period despite changes in total IgG class Mic antibody. During the year following delivery, thyrotoxicosis alone (Graves' disease) developed in 5 women. In the remaining 29 patients the absolute levels of Mic antibodies of IgG-4 subclass were similar 5 months postpartum in women with maximal serum thyrotropin (TSH) greater than 20 mU/1 (mean optical density in ELISA +/- s.d.; 0.84 +/- 0.538; n = 13) and in women with maximal TSH less than 10 mU/l (0.69 +/- 0.457; n = 16). In contrast, significantly higher values were observed for Mic antibody of IgG-1 subclass in patients with TSH greater than 20 mU/l (1.14 +/- 0.440) compared with women with maximal TSH less than 10 mU/l (0.65 +/- 0.289) (P less than 0.001 by t-test for groups). These results imply that the magnitude of Mic antibody levels of subclass IgG-1 but not IgG-4 is associated with the development of postpartum hypothyroidism and possibly with tissue destruction in autoimmune thyroid disease in general.

Thyroid autoantibody synthesis by lymphocytes from different lymphoid organs: fractionation of B cells on density gradients

Lymphocytes from thymus, blood, lymph nodes and thyroid tissue of patients with autoimmune thyroid disease have been assessed for their ability to synthesize thyroid autoantibodies spontaneously or following stimulation by Pokeweed mitogen (PWM). Blood and thymic lymphocytes synthesized IgG and microsomal or thyroglobulin antibodies of IgG class in response to PWM (and were therefore probably B-memory cells), while thyroid lymphocytes frequently secreted autoantibodies spontaneously. Lymph node lymphocytes resembled blood lymphocytes in terms of increased production of IgG in response to PWM; however, spontaneous secretion of thyroid autoantibodies was observed in some lymph node suspensions, and the magnitude of the increment in thyroid autoantibodies synthesized in response to PWM was lower than that observed for blood lymphocytes. Fractionation of B-cell enriched populations on density gradients and subsequent incubation of the fractions with T cells and PWM demonstrated that, whereas blood B cells capable of synthesizing autoantibody were found in both medium and low density fractions, lymph node precursors of thyroid autoantibody-secreting cells were associated almost exclusively with the light fractions. The presence in lymph nodes of small numbers of low density B cells, compared with a much higher proportion of the heterogeneous population capable of secreting IgG, could account for the discrepancy between the IgG and autoantibody response to PWM. Further, it seems likely that the density difference in the autoantibody precursor population of lymph nodes and blood is related to the difference in the state of activation of B cells in these lymphoid organs.

The effect of carbimazole on thyroid autoantibody synthesis by thyroid lymphocytes

Thyroid autoantibody synthesis was investigated in cultures of lymphocytes isolated from several sources, including thyroid and lymph nodes from patients with hyperthyroid Graves' disease treated preoperatively with carbimazole or propranolol. The ability of thyroid lymphocytes to secrete immunoglobulins, including thyroid microsomal or thyroglobulin autoantibodies, was markedly reduced in lymphocyte suspensions obtained from patients treated with carbimazole compared with suspensions from patients treated with propranolol. This effect (which was greater in individuals treated with carbimazole for longer periods) was attributable to a significant reduction in the number of viable lymphocytes present after the 14-day culture interval. In contrast, the type of preoperative therapy had little effect on cultures of lymphocytes obtained from lymph nodes draining the thyroid. Although it is not yet clear whether carbimazole exerts its effects in vivo by direct immunosuppression or indirectly by altering the thyroid microenvironment, our observations indicate that the fall in serum levels of thyroid autoantibodies that occurs during carbimazole therapy is related to an effect of the drug on lymphocytes within the thyroid.

Functional analysis of T and B cells from blood and thyroid tissue in Hashimoto's disease

B lymphocytes from Hashimoto blood and thyroid tissue have been cultured with autologous T cells from thyroid/blood to assess their ability to synthesise IgG and thyroid autoantibody. Thyroid B cells were able to synthesize microsomal antibody spontaneously in the absence of T cells or pokeweed mitogen (PWM) and this synthesis was increased in the presence of thyroid T cells without PWM or with blood T cells with PWM. In contrast, blood B cells did not secrete thyroid autoantibody spontaneously but could be induced to do so by thyroid T cells spontaneously or by blood T cells with PWM. Despite these differences, lymphocytes from blood and thyroid tissue secreted microsomal or thyroglobulin antibodies in culture which were similar in terms of the IgG subclass distribution. It would appear, therefore, that although the state of activation of B and T cells is different in blood and thyroid tissue, the precursors of thyroid autoantibody secreting cells are the same.

Characterization of lymphoid cells in the thyroid of patients with Graves' disease

The distribution and function of lymphoid cells has been investigated in thyroid glands obtained at operation from 16 patients with Graves' disease (GD) using a peroxidase technique to enumerate total T and B lymphocytes as well as helper and suppressor T cell subsets in tissue sections. A spectrum of lymphocytic infiltration was observed and the increase from minimal numbers of immune cells in some GD thyroids to focal thyroiditis in others appeared to be due to a rise in all the lymphoid cell types analysed and was not the result of major change in any one lymphoid compartment. T cells were diffusely distributed whereas B cells tended to occur in aggregates. Small numbers of OKT6+ cells (possibly antigen presenting cells) were observed although these were less numerous than in lymphoid organs such as tonsil. Lymphoid cell suspensions prepared from the thyroid tissue of five of seven GD individuals treated pre-operatively with propranolol synthesized thyroid autoantibodies spontaneously in culture and this synthesis was decreased in the presence of pokeweed mitogen. Since the OKT8+ T cell subset has been shown to suppress immunoglobulin production by lymphocyte cultures containing mitogen, it appears that the suppressor T cells, which are readily demonstrable in GD thyroid sections, are functional. It seems unlikely, therefore, that a defect in this type of suppression is responsible for the initiation or perpetuation of the autoimmune response to thyroid antigens in GD.

The distribution of microsomal and thyroglobulin antibody activity among the IgG subclasses

The IgG subclass distribution of autoantibodies to thyroglobulin (TgAb) and thyroid microsomes (MicAb) in 13 Hashimoto's sera has been investigated using an ELISA technique based on monoclonal anti-subclass antibodies. Considerable subclass restriction was observed with TgAb predominantly but not exclusively associated with IgG4 (mean %TgAb activity associated with IgG4 = 60%) and MicAb predominantly associated with IgG 1 (mean = 49%) and IgG4 (mean = 38%). The tendency for TgAb to be associated with IgG4 accorded with the weak complement fixing properties of this antibody whereas the association of MicAb with IgG1 was consistent with its complement fixing and cytotoxic properties.

Enrichment and depletion of thyroglobulin autoantibody synthesizing lymphocytes

Lymphocyte populations enriched for (or depleted of) a receptor for thyroglobulin (Tg) have been prepared from Hashimoto peripheral blood mononuclear cells (PBM) by rosetting with Tg coated erythrocytes. Removal of Tg binding cells from PBM or B cell preparations resulted in greater than 85% reduction in their ability to synthesize Tg antibody when stimulated with pokeweed mitogen (PWM) or EB virus (EBV); the depletion was specific since the ability of Tg receptor negative cells to secrete microsomal antibody and total IgG was unimpaired. Hashimoto lymphocytes (PBM or B cells) enriched for Tg binding cells produced only small amounts of Tg antibody when cultured with PWM even in the presence of irradiated T cells and monocytes; exposure to autoantigen followed by mitogen appeared to be inhibitory. However, the Tg receptor positive fraction was readily activated by EBV to synthesize Tg antibody with a specific activity 4-10 times higher than that secreted by unfractionated lymphocytes. The ability to isolate Tg specific B cells from peripheral blood will facilitate the development of EBV transformed cell lines secreting monoclonal Tg antibody and such antibodies will provide invaluable probes in the investigation of autoimmune thyroid disease.

The IgG subclass distribution of thyroglobulin antibody synthesized in culture

Thyroglobulin autoantibodies synthesized by Hashimoto lymphocytes in culture and present in serum have been analysed in terms of their IgG subclass distribution. The autoantibodies produced in vitro were frequently IgG4 or IgG1, whether pokeweed mitogen or Epstein-Barr virus was used to stimulate the cultures, and the subclass distribution of these thyroglobulin antibodies was similar to that observed in the patients' serum. It appears therefore that the antibodies synthesized in vitro in response to polyclonal B-cell activators resemble those produced in vivo, and it seems likely that both pokeweed mitogen and Epstein-Barr virus influence the same B-cell precursors of autoantibody-synthesizing cells, albeit by different mechanisms.

Thyroid autoantibody synthesis by cultures of thyroid and peripheral blood lymphocytes. II. Effect of thyroglobulin on thyroglobulin antibody synthesis

The influence of antigen (thyroglobulin, Tg) on Tg antibody synthesis has been investigated using cultures of Hashimoto thyroid and peripheral blood lymphocytes. In cultures of thyroid lymphocytes, Tg antibody synthesis was stimulated by a 24h pulse of Tg (10-100 micrograms/ml) and similar results were obtained using spleen lymphocytes from BALB/c mice immunized with human Tg. In contrast, Tg antibody synthesis by Hashimoto peripheral blood lymphocytes was not affected by similar concentrations of Tg (1-240 micrograms/ml) in the presence or absence of pokeweed mitogen (PWM). However, peripheral blood lymphocytes from two out of nine patients produced increased levels of Tg antibody in the presence of very low concentrations of Tg (50 ng/ml). This increase in Tg antibody production was accompanied by a rise in total IgG synthesis indicating that the response to Tg was polyclonal. On the basis of other unusual features of the lymphocyte cultures from these two patients including a relatively small response to PWM and evidence of circulating plasma cells, it is suggested that sufficient numbers of lymphocytes responsive to Tg are only released into the circulation during active phases of the disease process.

Thyroid autoantibody synthesis by cultures of thyroid and peripheral blood lymphocytes. I. Lymphocyte markers and response to pokeweed mitogen

Thyroid lymphocytes from Graves' and Hashimoto patients have been investigated and compared with lymphocytes from the peripheral blood. Considerably more lymphocytes (20-30 X 10(6)/g) could be isolated from Hashimoto thyroids than from Graves' tissue (1-5 X 10(6)/g) but the cell suspensions extracted from Hashimoto and Graves' glands were similar in terms of cell surface markers and the ability to synthesize immunoglobulin. Thyroid lymphocytes contained a lower proportion of T cells (OKT3+ cells) and in some cases more B cells than the peripheral blood but the ratio of helper to suppressor T cells (OKT4+:OKT8+ cells) was similar to the values obtained for blood lymphocytes. Further, thyroid lymphocytes (unlike blood lymphocytes) synthesized relatively large amounts of microsomal and/or thyroglobulin antibody when cultured in medium only and these levels were significantly decreased by the addition of pokeweed mitogen. The results of this study provide further evidence for the role of the thyroid as a major site of thyroid autoantibody synthesis and emphasize the importance of characterizing the cells infiltrating the gland in autoimmune thyroid disease.

An enzyme-linked immunoassay for thyroid microsomal antibodies

An enzyme-linked immunoassay (ELISA) for microsomal antibody is described. The method was found to be rapid, sensitive and precise and analysis of 115 serum samples showed good correlation between the ELISA and the conventional tanned red cell haemagglutination test. The presence of thyroglobulin antibody, rheumatoid factor, antinuclear factor or gastric parietal cell antibodies did not interfere in the microsomal antibody ELISA but some sera with mitochondrial antibody activity appeared to cause a non-specific effect. The ELISA was particularly useful for analysing microsomal antibody production by Hashimoto lymphocyte cultures and in some cases antibody synthesis could be studied in the absence of mitogen. The high capacity of the ELISA combined with its sensitivity suggest that it will be a valuable technique for studying microsomal autoantibody activity both in serum and in lymphocyte cultures.

D-Penicillamine-associated myasthenia gravis: immunological and electrophysiological studies

Immunological and electrophysiological features were investigated in a patient with rheumatoid arthritis who developed myasthenic symptoms after 10 months of treatment with D-penicillamine (D-pen). After an initial rise, acetylcholine receptor (AChR) antibodies gradually fell from 24.4 nmole alpha-bungarotoxin bound/liter to 1.8 nmole/liter following withdrawal of the drug, and this was associated with clinical and electrophysiological improvement. Immunoglobuline synthesis by peripheral blood lymphocytes cultured with pokeweed mitogen and D-pen was significantly increased at D-pen concentrations of 10-100 micrograms/ml in 2 patients with D-pen associated myasthenia gravis and 1 out of 3 normal individuals. Furthermore, lymphocytes from 1 myasthenic patient synthesized detectable AChR antibodies in vitro, and the amount of receptor antibody produced was increased in the presence of the drug. This effect was most marked at a concentration of 10 micrograms/ml which is thought to approximate the concentration in vivo. Our results confirm the in vivo findings of others that D-pen may have different effects on immunoglobulin production in different individuals and may also enhance the snythesis of at least 1 autoantibody, the AChR antibody.

Studies of thyroglobulin autoantibody synthesis using a micro-ELISA assay

Thyroglobulin autoantibody synthesis by Hashimoto lymphocyte cultures has been studied using an ELISA, a plaque assay and tanned red cell haemagglutination. The ELISA system was found to be the most suitable and using this method IgG-class thyroglobulin antibody synthesis was detectable in cultures of mitogen-stimulated lymphocytes from all 10 Hashimoto patients studied, but not in cultures of lymphocytes from 4 normal donors. The ELISA was also sufficiently sensitive to detect thyroglobulin antibody synthesis in mitogen-free lymphocyte cultures from 4 out of the 10 Hashimoto patients and consequently it should be possible to use this system to study the effect of various pathophysiological factors on autoantibody synthesis which would otherwise be masked by mitogenic stimulation.