Regulation of dendritic cell function by the ocular microenvironment in uveitis

The immune system protects the individual from a large range of infections. Although the immune response is highly efficient, this can result in some damage to surrounding areas. For the majority of organs this does not present a problem. However, in certain organs any significant immune mediated damage could threaten the survival of the individual. For these organs the immune response is carefully controlled and they are described as having immune privilege. The eye is a well studied example of an organ with immune privilege. It is clear that when inflammation occurs in the eye (uveitis) this contradicts the immune privileged status, with some patients suffering severe sight-threatening disease. The aim of our research is to identify the way in which the immune response is altered in uveitis. We wish to study the changes that occur in a specific immune cell, the dendritic cell, which acts as a co-ordinator of immune responses. By identifying the changes that occur in these cells in patients with uveitis we aim to identify new therapeutic options for this potentially blinding disease.

Uveitis (intraocular inflammation) is a group of diseases characterised by inflammation of the uveal tract. Although many cases resolve rapidly, a number will develop persistent severe sight-threatening inflammation. There is clear evidence that activated T cells are involved in the pathogenesis of uveitis (intraocular inflammation) in both humans and animal models of the disease. This suggests that mature dendritic cells (DC) are generated within the inflamed ocular microenvironment, in contrast to the immunosuppressive conditions reported to maintain immune privilege in this tissue. We propose to determine whether the ocular microenvironment (aqueous humour; AqH) in uveitis can deviate DC towards a pro-inflammatory phenotype. We will determine whether the resting non-inflammatory ocular environment (AqH) induces regulatory DC, and if this can be overcome by additional inflammatory/pathogen-derived signals. This will be compared to the capacity of AqH to regulate DC function altered during episodes of uveitis. In addition, we will use AqH from patients receiving glucocorticoid treatment at the time of sampling, allowing us to study the effects of this treatment on DC function. DC will be generated from peripheral blood monocytes by culture with IL-4 and GM-CSF. AqH will be added to immature DC alone and in combination with a number of pro-inflammatory stimuli (cytokines, Toll-like receptor ligands). The phenotype of the resulting DC will be studied, in particular the expression of a number of molecules involved in the stimulation of T cells and the secretion of key cytokines. DC will be cultured with CD4+ allogeneic T cells to determine their ability to stimulate T cell proliferation and effector function. We ultimately aim to identify the signals that regulate changes in DC maturation, and consequently the activation of T cells in uveitis, ultimately providing new therapeutic targets for this group of diseases.