Recognition of Epidermal Transglutaminase by IgA and Tissue Transglutaminase 2 Antibodies in a Rare Case of Rhesus Dermatitis

Summary

Dermatitis herpetiformis (DH) is a chronic inflammatory condition characterized by an autoimmune reaction between IgA and epidermal transglutaminase (eTG). DH develops in a very small portion of gluten-sensitive and/or celiac patients. The results of this study indicate that DH can also develop in a rhesus monkey host with symptoms of idiopatic dermatitis.

Abstract

Tissue transglutaminase 2 (tTG2) is an intestinal digestive enzyme which deamidates already partially digested dietary gluten e.g. gliadin peptides. In genetically predisposed individuals, tTG2 triggers autoimmune responses that are characterized by the production of tTG2 antibodies and their direct deposition into small intestinal wall ^1,2. The presence of such antibodies constitutes one of the major hallmarks of the celiac disease (CD). Epidermal transglutaminase (eTG) is another member of the transglutaminase family that can also function as an autoantigen in a small minority of CD patients. In these relatively rare cases, eTG triggers an autoimmune reaction (a skin rash) clinically known as dermatitis herpetiformis (DH). Although the exact mechanism of CD and DH pathogenesis is not well understood, it is known that tTG2 and eTG share antigenic epitopes that can be recognized by serum antibodies from both CD and DH patients ^3,4.

In this study, the confocal microscopy examination of biopsy samples from skin lesions of two rhesus macaques (Macaca mulatta) with dermatitis (Table 1, Fig. 1 and 2) was used to study the affected tissues. In one animal (EM96) a spectral overlap of IgA and tTG2 antibodies (Fig. 3) was demonstrated. The presence of double-positive tTG2+IgA+ cells was focused in the deep epidermis, around the dermal papillae. This is consistent with lesions described in DH patients ³. When EM96 was placed on a gluten-free diet, the dermatitis, as well as tTG2+IgA+ deposits disappeared and were no longer detectable (Figs. 1-3). Dermatitis reappeared however, based on re-introduction of dietary gluten in EM96 (not shown). In other macaques including animal with unrelated dermatitis, the tTG2+IgA+ deposits were not detected. Gluten-free diet-dependent remission of dermatitis in EM96 together with presence of tTG2+IgA+ cells in its skin suggest an autoimmune, DH-like mechanism for the development of this condition. This is the first report of DH-like dermatitis in any non-human primate.

Protocol

1. Skin biopsy sample collection

1. Prior to skin biopsy procedure, anesthetize animals intramuscularly with 2.5 mg/kg of tiletamine hydrochloride and zolazepam hydrochloride telazol mixture (Fort Dodge Animal Health, Fort Dodge, IA). Monitor the animals from administration of anesthetic until recumbency and then remove from their enclosure.
2. Remove the hair from the skin area of interest utilizing an Oster Golden A5 Single Speed Veterinary Clipper with a size 40 blade (Oster Professional Products, McMinnville, TN) and aseptically prepare with alternating betadine scrub and alcohol. Secure a sterile fenestrated drape over the selected biopsy site.

Discussion

Our newly established non-human primate model of gluten sensitivity was recently used to study the intestinal permeability changes triggered by dietary gluten ^5,6. Plasma tTG2 antibodies as well as intestinal tTG2+IgA+ deposits were detected in some gluten-sensitive macaques. Since we recently identified rare incidents of idiopathic dermatitis in colony rhesus macaques, where no usual (infectious/metabolic) etiology could be established, objective of this study was to evaluate if tTG2+IgA+ antibody deposits co.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Anti-Human IgA-FITC *	Sigma-Aldrich	F-5259	1:100 working dilution
Anti-Human tTG2	Thermo Fisher Scientific, Inc.	MS-300-P1ABX	1:100 working dilution
Anti-Mouse IgG1 **	Invitrogen	A-21124	1:1,000 working dilution
ToPro-3 DNA probe ***	Invitrogen	T-3605	1:1,000 working dilution
Zinc Formalin (Z-fix)	Anatech Ltd., Battle Creek, MI	171
OCT Freezing Medium	Sakura Finetek	4583
Cytoseal Mounting Medium	Richard-Allan Scientific	8312-4
Anti-Quenching Solution	Sigma-Aldrich	P 3130
Ethilon (Nylon Suture)	Ethicon Inc.	663G
Miltex Punch Dermal Biopsy Instrument	Miltex Inc.	NA
Oster Golden A5 Single Speed Vet Clipper with a size 40 blade	Oster Professional Products	78005-050
Leica Tissue Processor	Leica Microsystems	ASP300
Rotary Microtome	Microm International	HM325
Cryostat	Thermo Fisher Scientific, Inc.	HM560
Confocal Microscope	Leica, Wetzlar	TCS SP2
* Fluorescein isothiocyanate ** Secondary (Alexa Fluor 568-conjugated) antibody used after tTG2 primary antibody ** Dye