Research Areas

Overview – Mechanisms of Leukocyte Recruitment

The hypotheses which drive the work in our laboratory are that leukocyte recruitment is of central importance in inflammatory diseases, and the mechanisms whereby leukocytes enter sites of inflammation are highly complex and variable depending on the disease process and tissue involved.  As a result of this research, we hope to develop an understanding of the regulation of inflammation, and particularly leukocyte recruitment specific to each disease, a step which is a requirement for the development of the next generation of novel anti-inflammatory therapeutics. 

To achieve these aims, the major technique used by our laboratory is in vivo imaging, including multi-photon microscopy and other forms of intravital microscopy, to examine leukocyte function in intact tissues.  This allows us to gain an accurate understanding of leukocyte function and behaviour as it occurs in an inflammatory response.

In this work, we focus on the contributions of key inflammatory molecules, such as adhesion molecules, cytokines, chemokines, and signalling molecules, and tissue specificity of these responses. 

Mechanisms of Leukocyte Trafficking in the Glomerulus

The renal glomerulus is a specialized capillary bed which serves the function of blood filtration for the generation of urine.  However, the glomerulus is also the target of damaging immune responses in the diseases of glomerulonephritis and systemic lupus erythematosus (SLE).  During these responses, leukocytes accumulate within glomeruli, where they contribute to damaging the glomeruli, and cause glomerular injury and dysfunction.

In collaboration with Prof. Richard Kitching, we have been examining the mechanisms of leukocyte recruitment to this specialized vasculature, using intravital microscopy to examine the glomerular microvasculature in living mice.  These experiments have shown that leukocytes can be recruited to inflamed glomeruli without first undergoing an initial rolling interaction with the endothelium, a step typically required in other vascular sites (Kuligowski et al., J. Immunol., 2006).  Despite this, numerous adhesion molecules contribute to this process, indicating that this process is not a passive ‘trapping’ process.

In more recent work, we have demonstrated that antibodies which recognize myeloperoxidase (MPO) are capable of inducing glomerular leukocyte recruitment (Kuligowski et al., Blood, 2009).  These antibodies are equivalent to anti-neutrophil cytoplasmic antibodies (ANCAs) which are associated with glomerulonephritis and vasculitis in patients.

One of the aims of our ongoing work is to understand leukocyte recruitment and behaviour in the inflamed glomerulus, using multiphoton confocal microscopy to continuously image leukocytes present within inflamed glomeruli.

Role of Macrophage Migration Inhibitory Factor (MIF) in regulation of leukocyte recruitment

MIF is a pro-inflammatory protein which contributes to a wide range of pathologies.  We have shown that MIF promotes leukocyte-endothelial cell interactions in vivo (Gregory JL et al., Arthritis Rheum, 2004 & J. Immunol., 2006).  We have also shown that MIF promotes renal injury in a mouse model of SLE (Hoi AH et al., J. Immunol. 2006).  In ongoing work, we are investigating the mechanisms underlying this novel function of MIF.

In recent unpublished work we have observed that MIF mediates a pro-leukocyte recruitment effect in human endothelial cells.  In these experiments, we use siRNA technology to down regulate MIF in cells, and examine the ability of these modified endothelial cells to support interactions with human leukocytes under flow conditions.  Similarly, we are investigating the roles of MIF and its receptor CD74 in promoting leukocyte migratory function.  These ongoing experiments are demonstrating that MIF can affect leukocyte recruitment via effects on both leukocytes and endothelial cells.

Control of lymphocyte recruitment in skin inflammation

In forms of skin disease such as atopic dermatitis and allergic contact dermatitis, T lymphocytes are recruited to the skin where they coordinate an extremely debilitating inappropriate inflammatory response.  T cells of different phenotypes (CD8+, CD4+, T reg) can play different roles in this response. Given this, understanding the mechanisms of recruitment and interstitial migration of these different types of T cells is critical to unraveling this disease process.

We are using a model of T cell-mediated skin inflammation – contact sensitivity – to investigate the mechanisms of T cell recruitment to the inflamed skin.  Using advanced imaging, it is possible to identify different leukocyte subsets in the same blood vessel in the skin.  In this way, rare populations such as CD4 T cells or T regulatory cells can be identified (see pictures) and the mechanisms of their recruitment analysed.  In current experiments, we are using spinning disk confocal microscopy and multiphoton microscopy to examine the function of specific leukocyte subsets, both in the vasculature, and in the dermal interstitium.

Leukocyte function in Systemic Lupus Erythematosus

Systemic Lupus Erythematosus (SLE) is a life-threatening systemic autoimmune disease of unknown aetiology.  SLE patients mount an autoimmune response which induces damaging inflammation in a wide range of organs, including skin, kidneys and brain.  In collaboration with Prof. Eric Morand and the Sothern Health Lupus Clinic, we are examining the function of leukocytes from SLE patients. 

In this work, blood samples taken from patients attending the Lupus clinic are examined in the laboratory.  This work is revealing alterations in adhesive function of various leukocyte subsets in these patients, the mechanisms of which will be pursued over the next few years.