Antibody-dependent cell-mediated cytotoxicity against orbital target cells in thyroid-associated ophthalmopathy and related disorders; close relationship between serum cytotoxic antibodies and parameters of eye muscle dysfunction

Association Between Keratoconus and Thyroid Gland Dysfunction: A Cross-Sectional Case-Control Study

PURPOSE

To examine the clinical association between thyroid gland dysfunction and keratoconus.

METHODS

This was a cross-sectional case-control study conducted between May 2018 and July 2019. After performing Pentacam (Oculus Optikgeräte GmbH, Wetzlar, Germany) examination, flat, steep, and maximum simulated keratometric readings were recorded for each patient. Serum concentrations of free triiodothyronine, free thyroxine, and thyroid-stimulating hormone were measured. Further examinations by an endocrinologist were indicated for patients with positive laboratory results to confirm thyroid gland dysfunction.

RESULTS

One hundred eighty-seven patients with bilateral keratoconus and 187 sex- and age-matched healthy controls without keratoconus were analyzed. Mean age was 26.4 ± 8.2 years for the patients with keratoconus and 27.1 ± 9.4 years for the control patients, with no significant difference. The results showed that thyroid gland dysfunction prevalence was 10 of 187 patients with keratoconus (5.3%) and 2 of 187 control patients (1.1%), and the difference was statistically significant (P = .036). For the patients with keratoconus and thyroid gland dysfunction, 8 were women and 2 were men. Additionally, 6 patients (2 men and 4 women) had hyperthyrosis and 4 women had hypothyrosis. For controls, the two patients had hypothyrosis.

CONCLUSIONS

This study showed that there is a possible association between keratoconus and thyroid gland dysfunction, but more studies are needed to build upon these results. [J Refract Surg. 2020;36(4):253-257.].

Autoimmune Thyroid Disease and Keratoconus: Is There an Association?

PURPOSE

The association between autoimmune diseases and keratoconus (KC) has been proposed based on previous retrospective studies and case reports. The aim of our study is to investigate whether KC is associated with autoimmune thyroid disease. Methods. A comparative study was conducted on 131 adult subjects from September 2015 to May 2017 at Jordan University Hospital, Amman, Jordan. Subjects were classified into 2 groups: subjects with autoimmune thyroid disease, including Graves' disease and Hashimoto's thyroiditis (n = 68), and a healthy group for comparison (n = 63). Subjects with any other conditions known to be associated with KC were excluded. The diagnosis of KC was based on clinical and corneal topographic findings utilizing the Oculus-Pentacam machine. In addition, TSH and total T4 levels as well as thyroid peroxidase antibodies were measured in all study participants. Antithyroglobulin antibodies, thyroid stimulating immunoglobulin, thyroid ultrasound, and thyroid uptake and scan were also selectively performed in some participants.

RESULTS

This study included a total of 131 participants (101 females and 30 males), including patients and controls. In the multivariate analysis, autoimmune disease was not significantly associated with keratoconus (OR = 1.1; 95% confidence interval: 0.3, 3.8; p value = 0.353) after adjusting for age and gender.

CONCLUSION

This study did not show a statistically significant association between autoimmune thyroid disease and KC.

Autophagy plays a critical role in ChLym-1-induced cytotoxicity of non-hodgkin's lymphoma cells

Autophagy is a critical mechanism in both cancer therapy resistance and tumor suppression. Monoclonal antibodies have been documented to kill tumor cells via apoptosis, antibody-dependent cellular cytotoxicity (ADCC) and complement-dependent cytotoxicity (CDC). In this study, we report for the first time that chLym-1, a chimeric anti-human HLA-DR monoclonal antibody, induces autophagy in Raji Non-Hodgkin’s Lymphoma (NHL) cells. Interestingly, inhibition of autophagy by pharmacological inhibitors (3-methyladenine and NH₄Cl) or genetic approaches (siRNA targeting Atg5) suppresses chLym-1-induced growth inhibition, apoptosis, ADCC and CDC in Raji cells, while induction of autophagy could accelerate cytotoxic effects of chLym-1 on Raji cells. Furthermore, chLym-1-induced autophagy can mediate apoptosis through Caspase 9 activation, demonstrating the tumor-suppressing role of autophagy in antilymphoma effects of chLym-1. Moreover, chLym-1 can activate several upstream signaling pathways of autophagy including Akt/mTOR and extracellular signal-regulated kinase 1/2 (Erk1/2). These results elucidate the critical role of autophagy in cytotoxicity of chLym-1 antibody and suggest a potential therapeutic strategy of NHL therapy by monoclonal antibody chLym-1 in combination with autophagy inducer.

Eye muscle antibodies in Graves' ophthalmopathy: pathogenic or secondary epiphenomenon?

The extra ocular (eye) muscles are one of the principal tissues involved in the autoimmune-mediated inflammation of Graves' ophthalmopathy (GO). Several eye muscle proteins are targeted by autoantibodies or sensitized T lymphocytes, or both, and include: G2s, which is now identified as the terminal 141 amino acids of the winged-helix transcription factor FOXP1, the flavoprotein (Fp) subunit of the mitochondrial enzyme succinate dehydrogenase, the so-called "64kDa protein", a non-tissue specific membrane protein called 1D and the calcium binding protein calsequestrin. Of these, antibodies against G2s and Fp are the most sensitive markers of eye muscle damage in patients with thyroid autoimmunity even though neither antigen is specific to eye muscle and neither antibody is specific to GO. However, the recent finding that the calsequestrin gene is 4.7 times more expressed in eye muscles than other skeletal muscles suggests that we should reconsider the possible role of anti-calsequestrin autoantibodies in ophthalmopathy. GO may comprise two main subtypes with different pathogenetic mechanisms, namely ocular myopathy in which eye muscle inflammation predominates and congestive ophthalmopathy where inflammatory changes occur in the periorbital connective tissues in the absence of eye muscle dysfunction. Anti-G2s and anti-Fp antibodies are closely associated with the ocular myopathy subtype of GO while antibodies targeting type XIII collagen, the only member of the collagen family to have a transmembrane domain, are closely linked to congestive ophthalmopathy. Since both G2s and Fp are intracellular antigens it is unlikely that either antibody causes eye muscle fiber damage in GO, although a role in the later stages of the disease when the fiber has released its cellular contents has not been excluded. Eye muscle antibodies that are cytotoxic to eye muscle cells in antibody-dependent cell-mediated cytotoxicity (ADCC) are more likely to play a role in eye muscle fiber damage since they target a putative eye muscle cell membrane antigen, the identity of which is currently being investigated. While anti-G2s and anti-Fp antibodies are probably secondary to an underlying reaction, such as cytotoxic T lymphocyte targeting of an eye muscle membrane antigen that has yet to be identified, they are reliable markers of immunologically mediated eye muscle fiber damage in patients with Graves' hyperthyroidism. In conclusion, while a pathogenic role for eye muscle antibodies has not been excluded, they are most likely secondary to cytotoxic T cell reactions in GO and, as such, good markers of this autoimmune disease.

Development of an Animal Model of Autoimmune Thyroid Eye Disease

In previous studies we have transferred thyroiditis to naive BALB/c and NOD mice with human thyrotropin (TSH) receptor (TSHR)-primed splenocytes. Because the TSHR has been implicated in the pathogenesis of thyroid eye disease (TED) we have examined the orbits of recipients of TSHR-primed T cells, generated using a TSHR fusion protein or by genetic immunization. In the NOD mice, 25 of 26 animals treated with TSHR-primed T cells developed thyroiditis with considerable follicular destruction, numerous activated and CD8+ T cells, and immunoreactivity for IFN-γ. Thyroxine levels were reduced. Thyroiditis was not induced in controls. None of the NOD animals developed any orbital pathology. Thirty-five BALB/c mice received TSHR-primed spleen cells. Thyroiditis was induced in 60–100% and comprised activated T cells, B cells, and immunoreactivity for IL-4 and IL-10. Autoantibodies to the receptor were induced, including TSH binding inhibiting Igs. A total of 17 of 25 BALB/c orbits displayed changes consisting of accumulation of adipose tissue, edema caused by periodic acid Schiff-positive material, dissociation of the muscle fibers, the presence of TSHR immunoreactivity, and infiltration by lymphocytes and mast cells. No orbital changes or thyroiditis were observed in control BALB/c mice. We have induced orbital pathology having many parallels with human TED, only in BALB/c mice, suggesting that a Th2 autoimmune response to the TSHR may be a prerequisite for the development of TED.

Soluble intercellular adhesion molecule-1 (sICAM-1) concentrations in Graves' disease patients followed up for development of ophthalmopathy

It is commonly recognized that a few patients with Graves' disease (GD) develop an overt ophthalmopathy, although most of them show subclinical extraocular muscle enlargement by appropriate imaging techniques. At present, it is not possible to identify the subgroup of GD patients with subclinical retroorbital connective involvement. Recently, it has been shown that increase of soluble intercellular adhesion molecule-1 (sICAM-1) serum levels is correlated to clinical activity score in active Graves' ophthalmopathy (GO) patients with or without hyperthyroidism, suggesting that sICAM-1 serum values could reflect the degree of ocular inflammatory activity. The aim of this longitudinal study was to evaluate sICAM-1 serum levels in GD patients without clinical ophthalmopathy and to assess their possible relationship with occurrence of GO. We measured sICAM-1 serum levels in 103 initially hyperthyroid GD patients without clinical ophthalmopathy and in 100 healthy subjects. All patients were treated with methimazole for 2 yr. Sera were collected from all patients before treatment and then monthly for the first 6 months of therapy, every 2 months in the following 6 months, and finally at the end of the follow-up study. Patients developing GO were excluded from the follow-up at the onset of ophthalmopathy. During the follow-up 17 GD patients (16.5%, group 1) developed overt eye involvement (14 as active inflammatory ophthalmopathy and 3 as ophthalmopathy without clinical retroorbital connective inflammation) and 86 (83.5%, group 2) did not. At start of the study, the mean of sICAM-1 serum concentrations did not differ significantly between the 2 groups, but it was significantly higher than in controls in both groups. No significant correlation between serum sICAM-1 concentrations and free thyroid hormone levels was found in the 2 groups of patients. During the follow-up study, a further increase of sICAM-1 serum levels was observed in 12 of the 14 patients (85.7%) of group 1 who developed active inflammatory ophthalmopathy not only at the onset but also before clinical GO appearance. On the contrary, the 3 patients of group 1 that developed ophthalmopathy without clinical retroorbital inflammation did not show any further increase of sICAM-1 levels at every time of follow-up in comparison with the starting values, even if their sICAM-1 levels were always higher than in normal controls. Finally, group 2 patients showed significantly decreased sICAM-1 levels throughout the follow-up period when compared with the starting values, although they were still significantly higher than in controls. These results indicate that a further increase of sICAM-1 serum levels before the onset of clinical ophthalmopathy may be a marker of subclinical retroorbital connective inflammation in GD patients. Therefore, our study suggests that serial determinations of sICAM-1 serum levels could help to identify and trace at the right time those GD patients prone to developing active inflammatory ophthalmopathy.