Renal mesangial cell-macrophage interact

Auto-immune diseases are those caused by the body‘s own immune system. One such disease is systemic lupus erythematosus (SLE), associated with antibodies to DNA, and another is systemic vasculitis associated with antibodies to white blood cells called anti-neutrophil cytoplasm antibody (ANCA). Both diseases cause significant health problems such as kidney failure and lung disease. However, why certain individuals develop kidney problems while others avoid it remains unknown.
We have shown that the tendency to develop kidney disease is related to the expression of certain proteins (receptors) on circulating white blood cells and cells found within the kidney itself. Additionally, these cells interact with each other in a complex manner, influencing their ability to promote damage or induce tissue repair. Whether these proteins play as important a role in human disease as they do in animal models has never really been tested. I wish to test the role of these particular receptor proteins in kidney biopsies taken from patients with SLE and systemic vasculitis as well as in living cells from these patients. Understanding the key mechanisms that determine whether cells invading the kidney cause damage or repair, should allow such proteins to be developed as new therapeutic targets.

ANCA-associated vasculitides (AAV) and systemic lupus erythematosus (SLE) are autoimmune disorders that may result in glomerulonephritis, resulting in end stage kidney disease and a poor clinical outcome. The factors that determine particular organ involvement remain obscure, and the susceptibility to renal disease in certain individuals is therefore unknown. In both conditions, development of glomerulonephritis is critically associated with renal macrophage infiltration. However, recent evidence has highlighted the different macrophage phenotypes that may be generated and the altered outcomes of inflammation associated with them. Moreover, it has been reported that interaction of intrinsic renal cells with infiltrating leukocytes can influence the outcome of glomerulonephritis, but the mechanisms mediating these effects are not completely understood. I hypothesize that renal mesangial cell expression of mannose receptor and activatory Fc receptors promotes a pro-inflammatory macrophage phenotype and predisposes to glomerulonephritis. By contrast, mannose receptor deficiency or altered activatory:inhibitory Fc receptor expression ratio promotes an anti-inflammatory phenotype and will be associated with glomerular protection from disease. Our laboratory has already confirmed some of these findings in murine models of disease, but this has not been tested in clinical AAV/SLE or using human cells. I will test this idea by studying receptor expression in mesangial cells and macrophages in human disease and their interaction in vitro using a co-culture system.

I will use a variety of experimental techniques, including flow cytometry, real time PCR immunohistochemistry and ELISA to investigate receptor expression and cell phenotype, using renal biopsy material from patients, and laser capture microdissection of their glomeruli. Levels of expression will be correlated with clinical outcome and will be compared to that in disease controls. Additionally, cell culture experiments will allow specific manipulation of one or other receptor type, using RNA interference techniques, and the investigation, following such manipulation, of macrophage phenotype. These data will allow us to translate murine studies to the clinical setting and investigate whether these receptors may be novel targets for treatment of human disease.