Tom Flynn

Aqueous Humor Alloreactive Cell Phenotypes, Cytokines and Chemokines in Corneal Allograft Rejection

As biopsies are not taken at the time of human corneal allograft rejection, most information on the early cellular changes in rejection is from animal models. We examined the phenotype of alloreactive cells present in the human anterior chamber during corneal graft rejection by flow cytometry and quantified aqueous humor levels of cytokines and chemokines using cytometric bead array. Aqueous and peripheral blood samples were taken from patients with graft endothelial rejection (n = 11) and from control patients undergoing cataract surgery (n = 8). CD45+CD4+, CD45+CD8+ and CD45+CD14+ cells were found in aqueous during rejection; no CD45+ cells were seen in control samples. Higher proportions of CD45+ cells found in aqueous during rejection were CD14+, denoting monocyte/macrophage lineage, than were CD4+ or CD8+. Large elevations were seen in aqueous levels of IL‐6, MCP‐1 and IP‐10 during rejection compared with controls; smaller but still statistically significant increases were seen in MIP‐1α and eotaxin. The role of CD14+ cells in allorejection is unclear as is the potential of these chemokines and their receptors as therapeutic targets. Aqueous humor samples offer a unique opportunity to analyze components of the allogeneic response in direct contact with donor tissue but without artifacts inherent in examination of tissue.

Differential precision of corneal Pentacam HR measurements in early and advanced keratoconus

Background/aims Serial Scheimpflug corneal tomography to monitor the progression of keratoconus has become standard practice in most countries where corneal cross-linking is available. The tomographic definitions of progression are, however, poorly defined. The aims of this study were: (a) to estimate the 95% limits of intraobserver and interobserver agreement of corneal shape parameters on Pentacam in patients with keratoconus and (b) to investigate whether these limits of agreement varied according to disease severity. Methods 96 adult patients with keratoconus and no corneal scarring or history of previous surgery were recruited from a corneal clinic in a tertiary ophthalmology hospital. One eye of each subject was scanned twice by each of the two observers with the Pentacam HR. 95% limits of intraobserver and interobserver agreement for K1, K2, Kmax and corneal thickness at the thinnest corneal location (TCT) were calculated. Results Reproducibility of keratometry measures was better for early keratoconus than advanced keratoconus. In patients of Pentacam-derived Krumeich stage 1 or 2, the 95% limits of interobserver agreement for Kmax were from −0.90 to 1.01. In patients of Pentacam-derived Krumeich stage >2, the 95% limits of interobserver agreement for Kmax were from −3.71 to 3.86. Conclusions Keratometric measurements on Pentacam HR are less reproducible in advanced keratoconus than in early keratoconus. In patients of Pentacam-derived Krumeich stage 1 or 2, an increase in K1, K2 or Kmax of more than 1 dioptre is likely to represent the real change in the corneal shape.

Role of β‐chemokines in mast cell activation and type I hypersensitivity reactions in the conjunctiva: in vivo and in vitro studies

Summary:  Chemokines have a clearly defined role in mobilizing the recruitment of leukocytes to both healthy and inflamed tissues. This review details work from our and other laboratories, indicating that β‐chemokines may play important roles (i) in driving the terminal differentiation of mast cell precursors in mucosal tissues and (ii) in providing priming or costimulatory signals required for mast cell activation, leading to an antigen‐driven inflammatory response. These data stem from in vivo, ex vivo, and in vitro studies. Data are also presented that suggest that FcɛRI:chemokine receptor cross talk may involve spatiotemporal dynamics that may control the strength and nature of the complex activating signals controlling mast cell effector function.

The Dendritic Cell in Allergic Conjunctivitis

The acquired immune response in health and disease is initiated when foreign antigens are processed and presented to T lymphocytes via antigen-presenting cells as peptides in the context of Class I and II major histocompatibility complex antigens. It is now clear that there are various types of antigen-presenting cells and that the phenotype of these cells (together with the milieu of the tissue or lymphoid organ) dictates the nature of the immune response to the antigen. Very little is known about the phenotype, distribution, and roles of dendritic cell subtypes that contribute to the pathophysiology of type I hypersensitivity reaction in the ocular surface. We review what has been learned from studies of both human ocular allergy and murine models and comment on how this compares to allergic reactions in other mucosal tissues.

Allergy and Contact Lenses

Allergic conjunctivitis is a response to environmental allergens, as well as a genetic predisposition of the patient. It is classified as either acute (seasonal allergic conjunctivitis) or chronic (perennial allergic conjunctivitis, vernal keratoconjunctivitis, atopic keratoconjunctivitis and giant papillary conjunctivitis). The immune mechanism of these diseases will be discussed, as well as the allergic response to contact lens wear.

The effect of perioperative allergic conjunctivitis on corneal lymphangiogenesis after corneal transplantation

Introduction Perioperative allergic conjunctivitis accelerates the speed of corneal allograft rejection. This study examines the effect of allergic conjunctivitis, with and without dexamethasone treatment, on the early inflammatory response and lymphangiogenesis in the host cornea following corneal transplantation. Methods Allogeneic fully MHC-mismatched C57Bl/6 strain donor corneas were transplanted into naive A/J mice and into A/J mice with active allergic conjunctivitis. Further groups of allograft recipients with allergic conjunctivitis were treated post-operatively with twice daily topical dexamethasone 0.1% or phosphate-buffered saline. Mice were killed on days 2 and 6 and corneas were examined by (i) fluorescent immunohistochemistry of frozen sections using anti-CD11b, anti-F4/80 and anti-Gr-1 antibodies, or (ii) whole-mount staining with anti-LYVE-1 antibody. Lymphatic ingrowth and numbers of cells infiltrating the host cornea were compared between groups. Results There were significantly higher numbers of CD11b+ cells and LYVE-1+ vessels in the host cornea at day 2 in allergic compared with naive recipients, but no differences between naive and allergic recipients at day 6. In allergic eyes, dexamethasone treatment significantly inhibited LYVE-1 expression at days 2 and 6, and significantly improved allograft survival in recipients with allergic conjunctivitis if maintained for a week. Conclusions The innate immune response to allogeneic corneal tissue is more vigorous in the presence of allergic conjunctivitis than in naive eyes and is associated with accelerated lymphatic ingrowth to host cornea. Topical dexamethasone inhibits lymphatic ingrowth and this may be one mechanism by which topical steroid enhances graft survival.