Complement and neutrophil activation during cardiopulmonary bypass: a study in the complement-deficient dog.

Cardiopulmonary bypass (CPB) is known to cause complement and neutrophil activation, but the relative importance and interaction of these components in CPB-induced inflammation is unknown. In this study, a strain of dogs genetically deficient in the third component of complement (C3) was used to determine the contribution of C3 to neutrophil activation and pulmonary injury after CPB. Eleven dogs (5 C3-deficient and 6 controls) underwent 150 minutes of hypothermic CPB (28 degrees C) followed by 2 hours of observation. Before CPB, C3 levels were normal in controls and less than 1% of normal in C3-deficient dogs. In control dogs, functional activity of C3 decreased to 53.2% of baseline after 1 hour of CPB and there was immunohistochemical evidence of C3 deposition in lung after CPB; C3-deficient dogs had no C3 deposition in lung. Although similar degrees of neutropenia occurred during CPB in the two groups, expression of neutrophil adhesion molecule subunit CD18 was significantly lower in C3-deficient dogs than controls after 1 hour of CPB (45.9 +/- 3.7 versus 82.9 +/- 10.0 mean fluorescence units; p < 0.02). Postbypass lung tissue myeloperoxidase content was also less in C3-deficient dogs (43.8 +/- 4.6 versus 71.1 +/- 8.6 mumol x 10 mg-1 x min-1; p < 0.03). Cardiopulmonary bypass-associated lung injury (assessed by alveolar-arterial oxygen gradient, pulmonary vascular resistance, percent lung water, and light and electron microscopic appearance) was similar between groups. These results demonstrate that (1) C3 is deposited on pulmonary vascular endothelium during CPB and (2) C3 mediates increased expression of neutrophil CD18 and neutrophil sequestration in lung after CPB.(ABSTRACT TRUNCATED AT 250 WORDS)

Increased soluble endothelial adhesion molecules in rheumatoid arthritis correlate with circulating cytokines and depletion of CD45RO+ T-lymphocytes from blood stream.

Endothelial cells express adhesion molecules and release free forms (e.g., sELAM-1, sGMP-140, sICAM-1 and sVCAM-1). Compared with controls, the serum levels of these soluble adhesion molecules (SAM) were significantly increased in patients with rheumatoid arthritis. We investigated whether this was associated with the circulating cytokines and changes in peripheral blood T-lymphocyte (T-PBL) subsets. In healthy subjects, sELAM-1 correlated with the serum levels of Il-1 beta, Il-1 receptor antagonist (Il-1RA) and Il-6, while sGMP-140 was associated with Il-8, and sVCAM-1 was related to Il-7 and Il-8. Thus, already in controls, relations exist between the levels of SAM and circulating cytokines. The rheumatoid arthritis patients with low and high serum levels of IgA- and/or IgM-rheumatoid factors (RF) were separately analyzed. They have different cytokine profiles and showed distinct correlations. In patients with low RF, sGMP-140 and sVCAM-1 correlated with Il-1 beta, while sICAM-1 was associated with Il-7 and TNF-alpha. In patients with high RF, sELAM-1 correlated with Il-1RA, and sGMP-140 was associated with many cytokines (e.g., GM-CSF, MIP-1 alpha and TNF-alpha). In addition, lymphopenia (less than 1000 lymphocytes/microliters) was shown in 30% of the patients, and 20% (mostly with low RF levels) had reduced levels of "primed" CD45RO+ cells among T-PBL. In controls, cytokines (Il-7, Il-8 and GM-CSF), but not SAM, were associated with less CD45RO+ T-PBL. In patients with low RF only, sGMP-140 and sELAM-1 correlated with the depletion of "primed" CD4+ and CD8+ T-PBL respectively. In such patients, Il-1 beta and GM-CSF also correlated with less CD8+, CD45RO+ T-PBL. Thus, particularly in patients with low RF, increased SAM, possibly released by the endothelial cells, might reflect the cytokine-induced activation of the vascular endothelium and the extravasation of some CD45RO+ T-PBL.

Canine leukocyte integrins: characterization of a CD18 homologue.

The major characteristics of the canine CD18 leukocyte antigen family, defined by a murine monoclonal antibody CA1,4E9, are described. The overall molecular organization of this family of leukocyte integrins was similar to the human counterpart, and consisted of a common beta subunit of 95 kD (CD18) and non-covalently linked alpha subunits of 150 kD (CD11C), 165 kD (CD11b) and 180 kD (Cd11a). Conservation of CD18 epitopes between dog, human, feline, equine and bovine was observed. CD18 expression in lymphoid tissue had a characteristic pattern which was based on differences in the intensity of expression observed in different cell types. The expression of LeuCAMs in canine epidermotropic lymphosarcoma (mycosis fungoides) was also explored since LeuCAMs might be expected to play a major role in the tissue tropism of this tumor. Intense CD18 expression was observed in the malignant T cells which infiltrated the epidermis; these cells differed phenotypically from dermal T cells in that they often lacked Thy-1 expression. The potential pathogenetic significance of LeuCAM expression in canine mycosis fungoides is discussed.