Dilation by CGRP of middle meningeal artery and reversal by sumatriptan in normal volunteers

BACKGROUND

Calcitonin gene-related peptide (CGRP) plays a fundamental role in the pathophysiology of neurovascular headaches. CGRP infusion causes headache and dilation of cranial vessels. However, it is unknown to what extent CGRP-induced vasodilation contributes to immediate head pain and whether the migraine-specific abortive drug sumatriptan, a 5-hydroxytryptamine 1B/1D agonist, inhibits CGRP-induced immediate vasodilation and headache.

METHODS

We performed a double-blind, randomized, placebo-controlled, crossover study in 18 healthy volunteers. We recorded circumference changes of the middle meningeal artery (MMA) and middle cerebral artery (MCA) using magnetic resonance angiography before and after infusion (20 minutes) of 1.5 μg/min human αCGRP or placebo (isotonic saline) as well as after a 6-mg sumatriptan subcutaneous injection.

RESULTS

Compared with placebo, CGRP caused significant dilation of MMA (p = 0.006) and no dilation of MCA (p = 0.69). Sumatriptan caused a marked contraction of MMA (15%-25.2%) and marginal contraction of MCA (3.9% to 5.3%). Explorative analysis revealed that sumatriptan had a more selective action on MMA compared with MCA on the CGRP day (p < 0.0001) and on the placebo day (p = 0.007).

CONCLUSION

These data suggest that exogenous CGRP dilates extracranial vessels and not intracranial, and that sumatriptan exerts part of its antinociceptive action by constricting MMA and not MCA.

CLASSIFICATION OF EVIDENCE

This study provides Class I evidence that IV GCRP causes dilation of the MMA but not the MCA in healthy volunteers, and that sumatriptan reverses the dilation of the MMA caused by CGRP.

Is there loss or qualitative changes in the expression of thyroid peroxidase protein in thyroid epithelial cancer?

There is disagreement concerning the expression of thyroid peroxidase (TPO) in thyroid cancer, some studies finding qualitative as well as quantitative differences compared to normal tissue. To investigate TPO protein expression and its antigenic properties, TPO was captured from a solubilizate of thyroid microsomes by a panel of murine anti-TPO monoclonal antibodies and detected with a panel of anti-human TPO IgGkappa Fab. TPO protein expression in 30 samples of malignant thyroid tissue was compared with TPO from adjacent normal tissues. Virtual absence of TPO expression was observed in 8 cases. In the remaining 22 malignant thyroid tumours the TPO protein level varied considerably from normal to nearly absent when compared to normal thyroid tissue or tissues from patients with Graves' disease (range less than 0.5 to more than 12.5 microg mg(-1) of protein). When expressed TPO displayed similar epitopes, to that of TPO from Graves' disease tissue. The results obtained by the TPO capturing method were confirmed by SDS-PAGE and Western blot analysis with both microsomes and their solubilizates. The present results show that in about two-thirds of differentiated thyroid carcinomas, TPO protein is expressed, albeit to a more variable extent than normal; when present, TPO in malignant tissues is immunologically normal.

Comparative mapping of cloned human and murine antithyroglobulin antibodies: recognition by human antibodies of an immunodominant region

Antibodies (Ab) to thyroglobulin (Tg) are common in patients with autoimmune thyroid diseases, but it is currently unclear how Tg Ab are involved in the pathology of autoimmune thyroid disease. We have previously reported the isolation of immunoglobulin G (IgG)kappa and IgGlambda Fab from phage display combinatorial libraries from the cervical lymph node of a single Hashimoto's thyroiditis patient with a high anti-Tg titer. Sequence analysis of these Fab indicated a restricted heavy chain usage with a nonrestricted light chain usage, with Fab inhibiting the binding of patient Tg Ab by between 39% and 79%. Comparative mapping of nine each of these IgGkappa and IgGlambda Fab, and the patient serum from whom the Fab were derived, is described here, using a panel of 10 murine monoclonal antibodies (Mab) to human thyroglobulin (hTg). The Fab interacted principally with mAb defining the overlapping antigenic domains I and IV, previously characterized as the region recognized by the majority of patient serum Tg Ab. Tg Ab from serum of the patient from whom the Fab were derived were also directed at this region, suggesting that the Fab are representative of the Tg Ab present in this patient.

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.

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.

The antibody response in human autoimmune thyroid disease

1. The analysis of the antibody response in autoimmune thyroid disease has followed several historical trends. It was the investigation of thyroid-reactive antibody that allowed the initial characterization of the three principle thyroid autoantigens, thyroglobulin, thyroid peroxidase and the thyroid stimulating hormone receptor. 2. Analysis can be grouped under two broad areas: analysis of the physiological and pathological effects of the antibody, and analysis of the structure of the antibodies themselves. This review will focus on the latter. 3. Within recent years there has been a great increase in knowledge of thyroid-reactive antibody structure, principally through the adoption of phage display combinatorial library methodologies. While this latter technique has established some general principles for antibodies to thyroglobin and especially thyroid peroxidase, there is still a substantial gap in our knowledge of the antibody response to the thyroid stimulating hormone receptor. 4. Thyroid peroxidase antibodies have a relatively restricted V-region usage, and there is a correlation between the V-regions used and the epitope on thyroid peroxidase bound. In particular the V kappa light chain V kappa I(O12), is associated with reactivity to one epitope. 5. The purpose of this review is to bring together the latest results concerning the molecular analysis of the antibody response in autoimmune thyroid disease, to highlight areas of ignorance and conflict, and to discuss the methods adopted to circumvent the problems associated with analysis of the antibody response.

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.