Naomi Rebuck

Humoral and cellular activation in a simulated extracorporeal circuit.

Endothelial injury consequent upon widespread humoral and cellular activation is probably a major contributor to the phenomenon of cardiopulmonary bypass-induced organ dysfunction. This article reviews some of the mechanisms by which complement and neutrophil activation and interleukin-8 may be involved in this inflammatory response. In a model consisting of a simulated extracorporeal circulation we were able to demonstrate complement activation, profound and specific changes in neutrophil adhesion molecule expression, and interleukin-8 generation. The importance of these changes and their potential interactions are discussed.

Changes in neutrophil CD11b/CD18 andl-selectin expression and release of interleukin 8 and elastase in paediatric cardiopulmonary bypass

Children undergoing cardiopulmonary bypass (CPB) surgery for congenital heart defects develop an acute post-operative capillary leak which may be due to endothelial injury inflicted by adherent neutrophils (PMN). Direct immunofluorescence and flow cytometry were used to measure CD11a/CD18, CD11b/CD18 andl-selectin (l-s) expression on circulating PMN in CPB circuits containing human blood and in children undergoing CPB.In vitro, a general rise in CD11b/CD18 expression over 2h contrasted with complete loss ofl-s in a small but progressively increasing proportion of PMN. Marked but inconsistent changes in CD11b/CD18 andl-s were observedin vivo, in conjunction with fluctuations in circulating PMN count. Circulating IL-8 was detected starting at rewarming from hypothermia and reperfusion of the heart and lungs with a simultaneous, closely correlated rise in both PMN count and circulating elastase. IL-1 and TNF were not detected. These studies demonstrate changes in the pathways of PMN-endothelial interaction during and after CPB.

Pyoderma gangrenosum in a child with congenital partial deficiency of leucocyte adherence glycoproteins.

Congenital deficiency of β2 integrin leucocyte adhesion molecules is a rare immunodeficiency and is often fatal. Neutrophils are unable to bind to ligands on the endothelium, and so cannot leave the circulation during inflammation or infection. When leucocyte adhesion deficiency (LAD) is caused by abnormally low expression of β2 integrins, it is termed LAD type 1. We describe a 5‐year‐old girl with a history of recurrent bacterial infections since early childhood who developed necrotic skin ulcers resembling pyoderma gangrenosum and a persistent circulating neutrophilia. Histologically, the lesions showed deep ulceration with a diffuse lymphohistiocytic infiltrate, but with a relative sparsity of neutrophils. Subsequent investigation revealed a complete absence of CD11a/CD18 β2 integrins on the surface of the patients neutrophils, confirming the diagnosis of LAD type 1. The ulcers responded to treatment with oral prednisolone and colchicine.

Expression of soluble endothelial adhesion molecules in clinical cardiopulmonary bypass

Soluble endothelial adhesion molecule expression in clinical cardiopulmonary bypass (CPB) was investigated. Neutrophil-mediated endothelial injury plays an important role in CPB-induced organ dysfunction. The adhesion of neutrophil to the endothelium is central to this process. It has been well documented that CPB induces neutrophil activation and changes in neutrophil adhesion molecule expression, but the effect of CPB on endothelial cell activation is not known. This study was designed to measure soluble endothelial adhesion molecules during CPB. We made serial measurements (by specific enzyme-linked immunoabsorbent assay) of plasma levels of the soluble endothelial adhesion molecules, ICAM-1 and E-selectin in patients undergoing routine CPB (n =7) and in a control group (thoracotomy, n = 3). The results show an initial significant decrease during CPB followed by an increase in plasma E-selectin from 29.3 ± 5.1 ng/ml (mean ± SEM) prebypass to 34.0 ± 5.4 ng/ml at 48 h postbypass. Likewise, plasma ICAM-1 significantly decreased during CPB and then increased from 246.3 ± 38.0 ng/ml before bypass to 324.8 ± 25.0 ng/ml and 355.0 ± 23.0 ng/ml at 24 and 48 h after bypass, respectively. The rise in levels is statistically significant (p < 0.05). This study shows a decrease in circulating ICAM-1 and soluble E-selectin during CPB and an increase in their levels at 48 h after CPB.

Systemic inflammation during paediatric cardiopulmonary bypass: changes in neutrophil adhesive properties

a proportion, which grew steadily in number with time, lost all expression of L-selectin. IL-8 was detectable in circuits after 120 minutes. In most patients, neutrophil L-selectin rose during bypass or the early postoperative period, but no consistent pattern emerged. Small populations of L-selectin-negative neutrophils were observed in 6/10 patients during or immediately following bypass. After a neutropenia during bypass, there was a marked rise in neutrophil count at the

Changes in leucocyte counts and soluble intercellular adhesion molecule-1 and E-selectin during cardiopulmonary bypass in children

A consequence of cardiopulmonary bypass (CPB) in young children is postoperative capillary leak and associated pulmonary dysfunction. Neutrophils sequester in the lungs and may contribute to functional endothelial damage. The endothelial adhesion molecules, E-selectin and intercellular adhesion molecule-1 (ICAM-1), mediate sequential steps in adhesion by binding to leucocyte ligands. Circulating forms of these proteins have been identified. We studied changes in the plasma concentrations of soluble E-selectin and soluble ICAM-1 using fixed phase immunoassays, and associated leucocyte counts in 10 paediatric patients undergoing CPB. Concentrations of soluble L-selectin and soluble ICAM-1 consistently fell during CPB from preoperative levels of 89 ± 17 ng/ml (mean ± 2SEM) and 218 + 61 ng/ml, respectively, to 39 ± 7 ng/ml and 84 ± 24 ng/ml, respectively at the beginning of maximum hypothermia. The haemodilution that occurred during CPB largely explained this fall, but not the more marked decrease in white cell counts that also occurred over this period (6.7 ± 1.1 to 1.7 ± 0.5 × 109/l) which may reflect increased leucocyte sequestration. By 24 h postoperatively, levels of both soluble adhesion molecules approached preoperative concentrations, as did lymphocyte counts. In marked contrast, neutrophil counts rose appreciably towards the end of CPB, and continued to rise to a maximum of 10.9 ± 3.1 ×109/l during the immediate postoperative period and remained at these elevated levels 24 h later. Major consistent changes in circulating leucocyte numbers which occur early in cardiopulmonary bypass may reflect changes in adhesion to the endothelium and consequent sequestration. Alterations in the levels of soluble adhesion proteins may influence these processes.

Changes in leukocyte counts and soluble ICAMI and E-selectin during cardioputmonary bypass in children

A consequence of cardiopulmonary bypass (CPB) in young children is postoperative capillary leak and associated pulmonary dysfunction. Neutrophils sequester in itic lungs during CPU and may contribute to functional endothelial damage. Endothelial adhesion molecules E-selectin and ICAMI mediate sequential steps in adhesion by binding to leukocyte ligands. Circulating forms of these proteins have recently been identified. We therefore studied changes in the plasma concentrations of soluble E-selectin and soluble ICAMI using fixed phase immunoassays, and associated leukocyte counts in 10 pediatric patients undergoing CPB for corrective cardiac surgery. Preoperative concentrations of soluble E-selectin and soluble ICAM-1 consistently fell during CPB from 89±27ng/ml (mean ± 2SE) and 218±70ng/ml respectively, to 39±12ng/ml and 84 ± 28ng/ml respectively at the beginning of maximum hypothermia during CPB, The haemodilution that occurred during CPB largely explained this fall, but not a more marked decrease in while cell counts that also occurred over this period (6.66±1.23 to 1.73±1.73×109/l) which may reflect increased leukocyte sequestration. By 24 hours postoperatively, levels of both soluble adhesion molecules approached preoperative concentrations, as did lymphocyte counts. In marked contrast neutrophil counts rose appreciably at the end of CPB and during llie immediate postoperative period and remained at these elevated levels 24 hours later. Major consistent elungcs in circulating leukocyte numbers which occur early in CPB may reflect changes in adhesion to endothelium and consequent sequestration. Alterations in the levels of soluble adhesion proteins may influence these processes.