Abstract
Abstract: :
Purpose: In the steady state, the blood retinal barrier protects against immune effector molecules. Retinal microglia (MG) migrate and accumulate in response to neurodegeneration and although MG express MHC class II and CD45, their role during inflammatory responses remains undefined. The purposes of this study are to investigate changes in human MG phenotype, migration and activation status in response to pro and anti-inflammatory stimulation. Methods: Donor eyes were obtained from Bristol eye bank with consent and whole retina were removed. 5mm biopsy sections of retina were cultured on the membrane of a cell culture insert for 24, 48 and 72 hours. The effect of IFNγ-LPS stimulation and TGFß on MG migration, co-accessory molecule expression and activation (iNOS) were studied using immunofluorescence. Positive cells were counted in 6 fields of view within the retina tissue and at the tissue edge. Positive migratory cells were viewed on the membrane within 12 fields of view. Results: Microglia within the retina were positive for CD45 and MHC class II. MG accumulated at the tissue edge and on the membrane. MG that had migrated from the retina explant had adhered to the membrane and expressed CD45, whilst MHC class II expression was down regulated. In the presence of LPS-IFNγ stimulation, MG migration was reduced. The effect of the TGFß opposed the effects of LPS-IFNγ and maintained MG migration. Conclusion: Microglia readily migrate and this is inhibited following pro-inflammatory cytokine stimulation. TGFß maintains MG function and attenuates LPS-IFNγ effects. The data infers that MG respond co-ordinately, dependent upon initial cytokine stimulation.
Keywords: 470 microglia • 435 immunomodulation/immunoregulation • 437 inflammation