The IgG subclass distribution of thyroid autoantibodies

There have been several conflicting reports concerning the subclass distribution of thyroid autoantibodies. We have therefore reinvestigated this with both a radioimmunoassay and an ELISA based on the use of a variety of monoclonal antibodies. Our results demonstrate the presence of subclasses IgG1, IgG2, IgG3 and IgG4 in both thyroglobulin and microsomal autoantibodies from patients with either Graves' disease or Hashimoto's thyroiditis. However, in many patients there is over-representation of the IgG4 subclass. We also found marked differences in the binding characteristics of monoclonal antibodies directed against the same subclasses, underlining the need for appropriate selection of such monoclonal reagents in any assay.     

Glucocorticoid replacement therapy: are patients over treated and does it matter?

BACKGROUND AND OBJECTIVES Adequate assessment of patients on glucocorticoid replacement therapy is of great importance to avoid the consequences of under or over treatment, but no simple test is available for this. The aims of this study were (1) to assess adequacy of glucocorticoid replacement in hypoadrenal patients, (2) to correlate serum cortisol levels (cortisol day curve) with 24-hour urine free cortisol excretion and (3) to assess the impact of glucocorticoid dose optimization on markers of bone formation and bone resorption. DESIGN Cross-sectional study of current replacement therapy and a prospective study of the effect of dose alteration on bone turnover markers. PATIENTS Thirty-two consecutive patients on replacement glucocorticoid therapy (12 Addison’s disease, 20 hypopituitarism) from a University teaching hospital out-patient department. MEASUREMENTS Serum and urinary cortisol, osteocalcin, N-telopeptide of type I collagen (NTX) and bone mineral density. RESULTS 28/32 (88%) patients required a change of therapy; 24/32 (75%) a total reduction in dose, 18/32 (56%) a change in replacement therapy regimen or drug and 14/32 (44%) both changes. The mean daily dose of hydrocortisone was reduced from 29.5 ± 1.2 to 20.8 ± 1.0 mg. A significant correlation was found between peak cortisol and 24-hour urine free cortisol/creatinine (Spearman correlation r = 0.60, P < 0.0001; n = 51). Following hydrocortisone dose reduction, median osteocalcin increased from 16.7 μg/l (range 8.2–65.7) to 19.9 μg/l (8.2–56.3); P < 0.01, with no change in the NTX/creatinine ratio. CONCLUSIONS A high proportion of patients on conventional corticosteroid replacement therapy are over treated or on inappropriate replacement regimens. To reduce the long term risk of osteoporosis, corticosteroid replacement therapy should be individually assessed and over replacement avoided.     

Carboxylic acids and pH of denture plaque in patients with denture stomatitis

Denture stomatitis (DS) is the commonest form of oral Candida infection. Although it has been suggested that the acidic conditions prevailing beneath maxillary dentures may potentiate palatal inflammation associated with DS, little is known about the pH and carboxylic acids of denture plaque in subjects with and without the disease. Therefore, qualitative and quantitative analyses of short-chain carboxylic acids and pH of maxillary denture plaque of ten patients and nine controls were performed. Gram-stained smears of plaque revealed numerous yeasts in the DS plaque while yeasts were absent in control plaque. Acetate, lactate, propionate, succinate, formate and pyruvate were present in descending order of concentration in all plaque samples. DS plaque was more acidic and contained significantly lower concentrations of lactate ions than control plaque. These results imply that the carboxylic acids produced by the microflora of denture plaque may be aetiologically involved in the pathogenesis of denture stomatitis.     

Prediction of outcome in Graves' disease after carbimazole treatment

In a prospective study to determine which factors would predict remission or relapse, 65 patients with hyperthyroid Graves' disease were treated for six months with a blocking replacement regimen of carbimazole, 40 mg daily, and triiodothyronine (T3). They were followed for one year after stopping treatment, by which time 32 (49 per cent) had relapsed. Although the treatment protocol, relapse rate and frequency of the HLA-DR3 antigen in this population were similar to those of a regionally separate Graves' population investigated previously, the predictive value of HLA-DR3 status together with thyroid stimulating antibody (TSAB) levels was strikingly different. In the present study there was no significantly abnormal distribution of any HLA antigen in the relapse group compared with those patients who achieved remission. Thyroid stimulating antibodies were detected in 62 patients (95 per cent) and fell significantly (p less than 0.05) after carbimazole treatment, irrespective of DR3 status or outcome; TSAB levels only became undetectable in nine patients (28 per cent) who subsequently relapsed and in nine patients (30 per cent) who maintained remission. T3-suppressed 20 min 123I uptake fell equally after treatment in the relapse and remission groups but continued to fall thereafter in the group which maintained remission. In these patients, 123I uptake was significantly lower at the end of the study period than at the end of treatment (p less than 0.05). Serum free T4 levels were higher before treatment in the patients who later relapsed than in those whose disease remitted (p less than 0.02). This proved the only significant marker associated with outcome but was of little predictive value in any patient. This study highlights the problem in predicting the outcome of antithyroid drug treatment, since even within the same country under similar conditions, divergent results have been obtained. It appears that the loci controlling the immune response in Graves' disease are likely to include genes lying outside the HLA-DR region. The results also suggest that the immunological effects of antithyroid drugs are maintained after stopping treatment in those patients whose disease remits.     

Thyroid-stimulating antibody activity between different immunoglobulin G subclasses

To investigate the distribution of thyroid-stimulating antibody (TSAb) activity between IgG subclasses, sera from 11 patients with Graves disease (including the National Institute of Biological Standards and Control (NIBSC) Research Standard, long acting thyroid stimulator-B) were fractionated by chromatography on affinity columns of monoclonal IgG subclass antibodies or protein A to deplete all but a single subclass. The resulting fractions were 98% or more pure for a single subclass. In all 11 patients, TSAb activity appeared to be confined to the IgG1 fraction as determined by cAMP production on addition of the fractions to the FRTL-5 rat thyroid cell line. In all of eight specimens from seven patients so tested, the whole serum activity was recovered in the IgG1 fraction, after adjusting for the recovery of the isotype from the column. TSAb activity in one serum comprised both lambda and kappa light chains but was IgG1 restricted. This IgG subclass restriction was not found when the same fractions were tested for thyroglobulin, microsomal/thyroid peroxidase, or tetanus toxoid antibody activity. Together with previous results showing marked restriction of both light chain usage and isoelectric point of TSAb, these results support the idea that Graves' disease may be the result of an oligo- or possibly monoclonal response at the B cell level.     

Vitiligo melanocytes in long-term culture show normal constitutive and cytokine-induced expression of intercellular adhesion molecule-1 and major histocompatibility complex class I and class II molecules

The aetiology of vitiligo remains unclear. An autoimmune involvement has been suggested and, in this study, we examine whether melanocytes cultured from unaffected regions of the skin of vitiligo patients are more susceptible to immune attack by investigating constitutive and cytokine-stimulated expression of intercellular adhesion molecule-1 (ICAM-1) (under three media variants) and major histocompatibility complex (MHC) class I and class II (under one medium). Both normal and vitiligo melanocytes had similarly low constitutive expression of ICAM-1 and MHC class II molecules, whereas > 95% of cells had high constitutive expression of MHC class I. Normal and vitiligo melanocytes showed similar and significant increases in the expression of all three immune-related molecules in response to the cytokine, interferon-gamma. The expression of ICAM-1 was also similarly increased by the cytokine, tumour necrosis factor-alpha in both cells. Additionally, it was noted that, once the melanocyte cultures were established under experimental conditions, the rate of proliferation of vitiligo melanocytes did not differ significantly from that of normal melanocytes. In conclusion, we suggest that vitiligo melanocytes, once in culture, do not have intrinsic differences from normal melanocytes with respect to the expression of immune-related molecules.