Diminished Expression of Galectin-3 Around Blisters in Bullous Pemphigoid: An Immunohistochemistry Study

Background Bullous pemphigoid (BP) is a subepidermal blistering disorder caused by autoantibodies directed against hemidesmosomal proteins. Many patients with BP demonstrate circulating IgE autoantibodies. Although the role of IgE in the pathogenesis of BP is unknown, a correlation between IgE antibodies and eosinophilia has been observed. Soluble CD23 and galectin-3 are the main elements of the IgE group. The roles for CD23 in BP as a potential biomarker and IgE production regulator have been characterized, but no studies have evaluated any roles for galectin-3 in this disease. Objective In this study, we evaluated galectin-3 expression in BP as a first step in assessing its role in the pathogenesis of this autoimmune blistering process. Patients and Methods Sixty specimens diagnosed as BP were stained with antibodies to galectin-3. The percentages of nuclear and cytoplasmic galectin-3 expression and staining intensity were evaluated. Results There was a significant difference in galectin-3 cytoplasmic and nuclear expression within keratinocytes immediately surrounding and above the blisters: (1) cytoplasmic (mean = 17.2% ± 2.4%) vs adjacent unaffected skin (mean = 66.7% ± 2.0%, P < 0.0001) and (2) nuclear (mean = 1.9% ± 0.4%) vs adjacent unaffected skin (mean = 13.2% ± 1.2%, P < 0.0001). Conclusions Lower expression of galectin-3 around blisters in BP may suggest a role as an adhesion molecule. Loss of galectin-3 may add to the extension of blister formation by initiating cell-extracellular matrix disassembly and may be involved with the associated dermal inflammation and the eosinophil chemotaxis. Further studies will be necessary to elucidate the result of this observed loss on disease pathogenesis.

showed the highest intensity with very dark brown-colored stain. Interobserver concordance was high, as staining differences were prominent. All statistical calculations were performed using Microsoft Excel software. An alpha level of P < 0.05 was used to indicate significant differences.

results
All included specimens had been previously diagnosed as BP based upon the patients' clinical findings, histologic findings of a subepidermal blister that contained eosinophils in the blister cavity, and the demonstration of linear staining with IgG and C3 along the dermal-epidermal junction on contemporaneously received biopsies analyzed with direct immunofluorescence.
Galectin-3 showed lower expression above and lateral to the blisters compared to adjacent unaffected skin. We observed these changes in galectin-3 expression in both cytoplasmic and nuclear patterns around the blisters and adjacent unaffected skin. The galectin-3 expression was diffuse in adjacent unaffected skin with high intensity in both the cytoplasm and nucleus of keratinocytes. However, expression was diminished and irregular, with lower intensity above and lateral to the blisters. We observed a strong expression of galectin-3 in the inflammatory infiltrate and the surrounding vessels underlying the blisters, as well as the sebaceous glands near the blisters.
Out of 60 biopsies analyzed, this difference was noted   pressed in 5% and 1% in cytoplasmic and nuclear patterns respectively with the intensity of 1+ above ( Figure 2B) and lateral ( Figure 2D) to the blister, which were significantly

Introduction
Bullous pemphigoid (BP) is a subepidermal disorder described by autoantibodies against hemidesmosomes in the dermal and epidermal junction, usually in elderly patients.
BP usually starts with pruritis and urticaria and subsequently progresses to the development of blisters on the skin caused by subepidermal separation through the basement membrane at the level of the lamina lucida [1]. In addition to the IgG deposition seen along the dermal-epidermal junction (variably with depositions of IgM, IgA and C3, as well), most patients with BP present an autoimmune response by generating IgE autoantibody. Although the role of IgE in the pathogenesis of BP is unknown, a correlation between IgE antibodies and eosinophilia has been observed [2]. Soluble CD23 and galectin-3 are 2 main elements of the IgE group. While the role of soluble CD23 in BP as a potential biomarker, IgE production regulator and disease severity predictor has been characterized [3], no studies about putative roles for galectin-3 in BP have been performed [4].
Galectin-3 is a beta galactoside binding protein that is essential in the cell-to-cell or matrix adhesion. It broadly exists in the nucleus and cytoplasm of various cell types or may be found extracellularly on the cell surface [5]. As no studies have been reported on the role of galectin-3 immunohistochemical profile in pemphigoid disease, we attempted to evaluate the galectin-3 expression in patients with BP in the current study.

Materials and Methods
This retrospective study was approved by the institutional review board of our institution. We included 60 specimens from 55 patients diagnosed with BP between 2017 and 2020.
Five patients had 2 such biopsies.

Discussion
Galectin-3 is a β-galactoside binding lectin that is found in epithelial cells, including keratinocytes. It is expressed in the nucleus and cytoplasm of normal keratinocytes and related Hemidesmosomes are composed of plectin 1a and integrin

Conclusions
We demonstrated lower expression of galectin-3 around the blisters in BP specimens. The pathogenesis of the blister formation may be associated, at least in part, with altered expression of galectin-3. Further studies are required to elucidate the result of this loss on the pathogenesis of the observed histologic findings and determine the exact pathogenesis of blister formation.