REVIEWS
At the present time, corneal transplantation (keratoplasty) is one of the most frequent modes of solid tissue transplants in the world. Unlike other kinds of transplants, corneal grafting is often performed without tissue typing and systemic immunosuppression.
High frequency of transparent corneal engraftment (up to 90% of cases) in the absence of risk factors is due to special immunoprivileged area in the anterior eye segment (functionally, a structural aggregation of the cornea and anterior chamber, AC) accomplished by local and systemic immunoregulatory mechanisms, i.e., phenomenon of immune deviation associated with anterior chamber of the eye (ACAID), components of the internal liquid medium, a watery moisture with immunosuppressive properties, e.g., IL-1ra, TSP-1,TGF-β2, regulatory complement proteins, α-MSH (alpha-melanocyte stimulating hormone), VIP (vasoactive intestinal peptide), indolamine 2,3-dioxygenase (IDO), calcitonin-gene-bound peptide (CGRP), somatostatin, etc.
In addition to ACAID and liquid AC components, a contribution to the maintenance of immune privilege which is extremely important for a successful outcome of keratoplasty, is provided by other mechanisms, in particular, immunologically active membrane-associated molecules of corneal endothelium, i.e., PDL-1 (Programmed death ligand 1), and sVEGFR-1, sVEGFR-2, sVEGFR-3 involved in maintaining avascularity of the corneal tissue. Disturbances of the immune privilege of the cornea promotes activation of immune recognition with switching the effector mechanisms of transplantation immunity, thus leading to subsequent development of the tissue incompatibility reaction and clouding of transplanted cornea. Graft rejection can be localized in any of the corneal cell layers, including epithelium, stroma, and endothelium. Endothelial rejection causes the most severe affection of visual functions, due to the inability of local endothelial recovery, and water accumulation due to the endothelial dysfunction.
Graft rejection is clinically characterized by edema and the presence of inflammatory cells, either circulating in the anterior chamber, or forming precipitates on the graft endothelial cells.
A number of factors are associated with an increased risk of corneal graft rejection, including the degree of inflammation and/or vascularization of the transplant bed i.e., location of the donor cornea, repeated keratoplasty, allosensitization due to other cellular transplants, including bone marrow, blood transfusions, pregnancy, etc., as well as allergic and systemic diseases.
This review article considers and systematizes the data from the literature concerning studies of the factors determining the immune privileged state of cornea, and the ACAID phenomenon, their role in development of allotolerance in corneal transplantation, highlights the main conditions required for triggering the tissue incompatibility reactions, discusses the mechanisms of allogeneic recognition and effector stage of the immune response, destruction of corneal allografts.
ORIGINAL ARTICLES
SHORT COMMUNICATIONS
Previous studies reported some associations between IgA and IgG antibodies specific to benzo[a] pyrene (Bp), estradiol (Es) and progesterone (Pg), and breast cancer (BC) in postmenopausal women. Likewise, the individual ratios of these antibodies (IgA-Bp/IgA-Pg, IgG-Bp/IgG-Pg, IgG-Es/IgG-Pg, IgG-Es/IgG-Pg) were associated with BC. It was suggested that development of antibodies to chemical carcinogens and steroid hormones was determined by functional polymorphisms of cytokine genes. The purpose of this study was to identify the suggested associations of antibodies to Bp, Es, Pg, and their individual ratios to the following gene polymorphisms: IL1RN (rs4251961), IL1B (rs16944), IL6 (rs1800795, rs1800796, rs1554606), IL8 (rs4073), TNFA (rs1800629) and CD40 (rs6074022) detected in postmenopausal healthy women and BC patients.
The serum IgA and IgG antibodies specific to Bp, Es and Pg were studied in 470 healthy women and 995 BC patients by non-competitive solid phase immunoassay. The conjugates of Bp, Es, Pg with bovine serum albumin were used as adsorbed antigen. The goat antibodies against human IgA or IgG conjugated with horseradish peroxidase were used for the detection of bound hapten-specific antibodies. Cytokine gene polymorphisms were analyzed by the real-time PCR.
Associations between the studied antibodies and their ratios with the gene polymorphisms in IL1RN (rs4251961), IL6 (rs1800795), TNFA (rs1800629) and CD40 (rs6074022) were found in healthy women. Higher individual ratios of IgA-Bp/IgA-Pg (p = 0.0001), IgG-Bp/IgG-Pg (p < 0.0001), IgG-Es/IgG-Pg (p = 0.0003) were associated with the allele C gene IL1RN. The higher IgG-Es levels were more common in the persons with allele G gene IL6 (p = 0.007), and with C allele of CD40 gene (p = 0.005). The high IgA-Pg levels were associated with A allele gene of TNFA (p = 0.008). Associations of antibodies were found only with genes polymorphisms in CD40 (rs6074022) in BC patients. Higher IgG-Es levels were more common in persons with allele T gene CD40 (p = 0.007).
In conclusion, we revealed the participation of cytokines in immune regulation of antibody genesis for environmental chemical carcinogens and endogenous steroid hormones in healthy women and BC patients. The future investigations of antibodies specific to Bp, Es and Pg combined with the analysis genes polymorphisms in cytokines will be useful for detection of the individual hormone-dependent cancer risks in humans.
IMMUNOLOGICAL METHODS
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