Modulation of HLA-DR and CD1a expression on human cornea with low-dose UVB irradiation

Exogenous control of the expression of Group I CD1 molecules competent for presentation of microbial nonpeptide antigens to human T lymphocytes

Group I CD1 (CD1a, CD1b, and CD1c) glycoproteins expressed on immature and mature dendritic cells present nonpeptide antigens (i.e., lipid or glycolipid molecules mainly of microbial origin) to T cells. Cytotoxic CD1-restricted T lymphocytes recognizing mycobacterial lipid antigens were found in tuberculosis patients. However, thanks to a complex interplay between mycobacteria and CD1 system, M. tuberculosis possesses a successful tactic based, at least in part, on CD1 downregulation to evade CD1-dependent immunity. On the ground of these findings, it is reasonable to hypothesize that modulation of CD1 protein expression by chemical, biological, or infectious agents could influence host's immune reactivity against M. tuberculosis-associated lipids, possibly affecting antitubercular resistance. This scenario prompted us to perform a detailed analysis of the literature concerning the effect of external agents on Group I CD1 expression in order to obtain valuable information on the possible strategies to be adopted for driving properly CD1-dependent immune functions in human pathology and in particular, in human tuberculosis.

[Clinical aspects of corneal burns]

Clinical aspects and prognosis of corneal burns mainly depend on the agent responsible for the trauma. The most severe burns are caustic burns, which should be classified as burns caused by basic agents, associated with deep and prolonged injuries, and burns caused by acidic agents, associated with more superficial injuries. At the acute stage, caustic burns induce epithelial defects, corneal edema, and ischemic necrosis of the limbus, conjunctiva, iris and ciliary body. At the early stage, reepithelialization occurs and is often associated with corneal vascularization and stromal infiltrates, followed by corneal scar formation. At the chronic stage, the following complications are possible: corneal scars, limbal stem cell insufficiency, lachrymal insufficiency, irregular astigmatism, ocular surface fibrosis, cataract, glaucoma, decreased intraocular pressure, and ocular atrophy. The Ropper-Hall classification is based on the extent of limbal ischemia. Thermal burns induce epithelial defects at the acute stage, with the more severe forms giving the same complications as caustic burns. Radiation-related burns can be caused by ultraviolet radiations (acute epithelial keratitis, pterygium, droplet-like keratitis), microwaves, infrared radiations, ionizing radiations or, laser radiations. Electrical burns are often a result of torture and give corneal stroma opacification.

In situ immunohistochemical study of Bcl-2 and heat shock proteins in human corneal endothelial cells during corneal storage

AIM

To investigate the expression of Bcl-2 and heat shock proteins (HSPs), which are known to increase cell survival, in human corneal endothelial cells (HCECs) of corneas stored in organ culture.

METHODS

32 paired corneas were randomly assigned to either a short or a long storage time. The flat mounts of endothelium were examined after immunostaining with monoclonal antibodies to Bcl-2 and HSP 27, 60, 70, and 90.

RESULTS

HCECs expressed generally all the proteins studied. Bcl-2 expression was weaker in the long stored corneas (p=0.035). There was no relation between immunostaining, age, sex, or death to culture time. Frequently some Descemet membranes carried negative cells preferentially located in folds and exhibiting morphological changes consistent with swelling cells corresponding to early stages of apoptosis.

CONCLUSION

Expression of these cytoprotective proteins reflects the high level of HCEC resistance to stresses induced by organ culture. The decreased immunostaining of Bcl-2 in the long storage group could act in cellular loss currently observed with storage time. The negativity of Bcl-2 and HSP labelling in corneal folding may be related to apoptosis.