Leukocyte transmigration and gene expression in healthy subjects and patients with renal failure-application of the skin chamber technique

Abstract

The migration of leukocytes from the peripheral circulation into infected or injured tissue is a fundamental step in the host-defense mechanism. The skin chamber technique is a well documented method for studies of leukocyte trans migration and function in vivo. Patients with chronic renal failure are highly susceptible to infections and one contributing factor is dysfunctional leukocytes.

The aim of this thesis was to analyze the transmigration and state of activity in terms of adhesion molecule expression of in vivo transmigrated neutrophils and monocytes in healthy subjects and patients with renal failure, using the skin chamber technique.

Results: We have shown that monocytes that have been newly recruited to sites of interstitial inflammation in vivo, prior to their differentiation to macrophages, have a preserved ability to respond to challenge with bacterial peptides in terms of CD11b upregulation and intracellular hydrogen peroxide production in healthy subjects. This indicates that newly recruited monocytes play an important role in the immediate response against invading pathogens. In order to study the immune response at the interstitial site in patients with renal failure, monocyte transmigration and state of activity in terms of CD11b expression was analysed in patients with moderate to severe renal failure, patients on peritoneal dialysis and healthy subjects. In addition to monocytes, we investigated granulocytes from patients on peritoneal dialysis.

Transmigrated monocytes from patients with severe renal failure had a reduced ability to upregulate CD11b at the interstitial site of inflammation compared with cells collected from healthy subjects. The reduced CD11 b expression was more dependent on cellular factors than on the concentration of soluble mediators in the interstitial milieu. A reduced ability to upregulate CD11b was also observed in monocytes and neutrophils from patients on peritoneal dialysis. Since CD11 b plays a crucial role for innate immunity to invading microbes, these phenotypic aberrations may have pathophysiological consequences in terms of increased susceptibility to infectious diseases, a phenomenon observed in patients with renal failure.

In order to understand the molecular mechanisms that contribute to the leukocyte dysfunction observed in patients with renal failure, gene expression profiling on peripheral and in vivo transmigrated neutrophils from patients with severe renal failure and healthy subjects was performed. Neutrophils from patients with renal failure showed a divergent gene expression pattern, compared to neutrophils from healthy subjects in the peripheral circulation and at the site of interstitial inflammation. The greatest differences were observed at the interstitial site. At that site, neutrophils from patients with renal failure had a higher gene expression of proinflammatory cytokines and cytokines involved in T-cell cell recruitment.

In conclusion, a gradual loss of renal function is associated with impaired leukocyte CD11b expression at the interstitial site of inflammation. This is partly improved by renal replacement therapy. Furthermore, in vivo transmigrated neutrophils from patients with renal failure have a more pronounced expression of proinflammatory genes compared to healthy subjects. Our findings contributes to a better understanding of factors involved in the higher rate of infections observed in patients with renal failure. These data may generate potential platform for new therapeutic interventions.