Transmigration of Blood Leukocytes into the Peritoneal Cavity is Related to the Upregulation of ICAM-1 (CD54) and MAC-1 (CD11b/CD18) Adhesion Molecules

Background

Migration of blood leukocytes into the peritoneal cavity of patients treated with peritoneal dialysis appears to be an important mechanism to prevent and fight peritonitis. To study the role of adhesion molecules in the process of leukocyte transmigration, we compared the expression of several adhesion receptors between peripheral blood monocytes and macrophages isolated from overnight dwell effluents.

Methods

The study was performed in 12, stable, infection-free patients treated with continuous ambulatory peritoneal dialysis (CAPD) and in 9 patients during peritonitis. In another set of experiments, we analyzed the expression of these molecules on blood leukocytes in 10 predialysis chronic renal failure (CRF) patients and 9 healthy controls. Peritoneal cells from an 8-hour dwell were isolated by centrifugation. Expression of adhesion receptors CD11a, CD11b, CD18, CD49d, and CD54 on blood and peritoneal leukocytes was measured using flow cytometry.

Results

In macrophages from the uninfected effluents, expression of both subunits of Mac-1 integrin receptor (CD11b and CD18) and intercellular adhesion molecule (ICAM)-1 receptor (CD54) was upregulated compared to peripheral blood monocytes from the same patients. The median value of mean fluorescence intensity in blood and effluent was 760.3 versus 1085.8 for CD11b ( p = 0.013), 288.8 versus 448.6 for CD18 ( p = 0.003), and 186.1 versus 365.7 for CD54 ( p = 0.001). The same adhesion receptors were also significantly upregulated on peritoneal macrophages and neutrophils during peritonitis compared to blood leukocytes. Blood leukocytes from CAPD and CRF patients showed higher expression of CD54 and CD49d molecules compared to leukocytes from healthy controls.

Conclusions

These data suggest that transmigration of blood leukocytes into the peritoneal cavity during uncomplicated dialysis and in peritonitis is related to selective upregulation of ICAM-1 (CD54) and Mac-1 (CD18/CD11b) receptors.

Dendritic Cells as Arbiters of Peritoneal Immune Responses

During the past few years, there has been a substantial increase in the understanding of innate immunity. Dendritic cells are emerging as key players in the orchestration of this early phase of immune responses, with a role that will translate into the subsequent type of adaptive immune response against infection. Here we provide an overview of dendritic cell differentiation and function, with particular emphasis on those features unique to the immune defense of the peritoneal cavity and in the context of peritoneal dialysis-associated immune responses. The reader is referred to the primary references included in the accompanying list for specific details in this fascinating field.