αβ TCR⁺ T cells, but not B cells, promote autoimmune keratitis in b10 mice lacking γδ T cells

Immunosenescence, immunotolerance and rejection: clinical aspects in solid organ transplantation

As a consequence of increased lifespan and rising number of elderly individuals developing end-stage organ disease, the higher demand for organs along with a growing availability for organs from older donors pose new challenges for transplantation. During aging, dynamic adaptations in the functionality and structure of the biological systems occur. Consistently, immunosenescence (IS) accounts for polydysfunctions within the lymphocyte subsets, and the onset of a basal but persistent systemic inflammation characterized by elevated levels of pro-inflammatory mediators. There is an emerging consensus about a causative link between such hallmarks and increased susceptibility to morbidities and mortality, however the role of IS in solid organ transplantation (SOT) remains loosely addressed. Dissecting the immune-architecture of immunologically-privileged sites may prompt novel insights to extend allograft survival. A deeper comprehension of IS in SOT might unveil key standpoints for the clinical management of transplanted patients.

Mucosal immunology of the ocular surface

The eye is a sensory organ exposed to the environment and protected by a mucosal tissue barrier. While it shares a number of features with other mucosal tissues, the ocular mucosal system, composed of the conjunctiva, Meibomian glands, and lacrimal glands, is specialized to address the unique needs of (a) lubrication and (b) host defense of the ocular surface. Not surprisingly, most challenges, physical and immunological, to the homeostasis of the eye fall into those two categories. Dry eye, a dysfunction of the lacrimal glands and/or Meibomian glands, which can both cause, or arise from, sensory defects, including those caused by corneal herpes virus infection, serve as examples of these perturbations and will be discussed ahead. To preserve vision, dense neuronal and immune networks sense various stimuli and orchestrate responses, which must be tightly controlled to provide protection, while simultaneously minimizing collateral damage. All this happens against the backdrop of, and can be modified by, the microorganisms that colonize the ocular mucosa long term, or that are simply transient passengers introduced from the environment. This review will attempt to synthesize the existing knowledge and develop trends in the study of the unique mucosal and immune elements of the ocular surface.

γδ T Cell-Dependent Regulatory T Cells Prevent the Development of Autoimmune Keratitis

To prevent potentially damaging inflammatory responses, the eye actively promotes local immune tolerance via a variety of mechanisms. Owing to trauma, infection, or other ongoing autoimmunity, these mechanisms sometimes fail, and an autoimmune disorder may develop in the eye. In mice of the C57BL/10 (B10) background, autoimmune keratitis often develops spontaneously, particularly in the females. Its incidence is greatly elevated in the absence of γδ T cells, such that ∼80% of female B10.TCRδ(-/-) mice develop keratitis by 18 wk of age. In this article, we show that CD8(+) αβ T cells are the drivers of this disease, because adoptive transfer of CD8(+), but not CD4(+), T cells to keratitis-resistant B10.TCRβ/δ(-/-) hosts induced a high incidence of keratitis. This finding was unexpected because in other autoimmune diseases, more often CD4(+) αβ T cells, or both CD4(+) and CD8(+) αβ T cells, mediate the disease. Compared with wild-type B10 mice, B10.TCRδ(-/-) mice also show increased percentages of peripheral memory phenotype CD8(+) αβ T cells, along with an elevated frequency of CD8(+) αβ T cells biased to produce inflammatory cytokines. In addition, B10.TCRδ-/- mice have fewer peripheral CD4(+) CD25(+) Foxp3(+) αβ regulatory T cells (Tregs), which express lower levels of receptors needed for Treg development and function. Together, these observations suggest that in B10 background mice, γδ T cells are required to generate adequate numbers of CD4(+) CD25(+) Foxp3(+) Tregs, and that in B10.TCRδ(-/-) mice a Treg deficiency allows dysregulated effector or memory CD8(+) αβ T cells to infiltrate the cornea and provoke an autoimmune attack.

Combined anterior chamber washout, amniotic membrane transplantation, and topical use of corticosteroids for severe peripheral ulcerative keratitis

PURPOSE

The aim of this study was to evaluate the efficacy of anterior chamber washout, amniotic membrane transplantation, and topical use of corticosteroids in the treatment of severe peripheral ulcerative keratitis with membranous endothelial exudation.

METHODS

Twelve patients (12 eyes) with severe corneal ulceration were included. All ulcers were located at the corneal periphery, accompanied by central corneal epithelial defects and stromal edema. Membranous endothelial exudates were observed by anterior segment optical coherence tomography. The duration of the ulcers was 1 to 10 months (mean, 3.0 ± 2.9 months) before the patients visited our institution. Corneal inflammation and ulceration could not be controlled after 2 weeks of topical antiinflammation treatment. Bacterial, fungal, and Acanthamoeba infections were not detected. Surgical treatment was performed. After the necrotic corneal tissue was cut, exudation clinging to the endothelium was removed. Then, amniotic membrane was placed on the corneal lesion. Postoperatively, corticosteroid eye drops and topical and systemic antiinflammation medication were given. Healing of corneal ulcers and improvement of stromal edema were detected by slit-lamp microscopy. All patients were followed up for 3 to 15 months (mean, 6.5 ± 3.7 months).

RESULTS

All corneal ulcers healed by 1 to 2 weeks after surgery. The corneal stromal edema subsided within 1 month. All patients achieved a stable ocular surface. There was no recurrence during the follow-up.

CONCLUSIONS

Anterior chamber washout and amniotic membrane transplantation combined with topical corticosteroids seems to be effective for the treatment of severe peripheral ulcerative keratitis with endothelial exudates.