Interdependency of CEACAM-1, -3, -6, and -8 induced human neutrophil adhesion to endothelial cells

Members of the carcinoembryonic antigen family (CEACAMs) are widely expressed, and, depending on the tissue, capable of regulating diverse functions including tumor promotion, tumor suppression, angiogenesis, and neutrophil activation. Four members of this family, CEACAM1, CEACAM8, CEACAM6, and CEACAM3 (recognized by CD66a, CD66b, CD66c, and CD66d mAbs, respectively), are expressed on human neutrophils. CD66a, CD66b, CD66c, and CD66d antibodies each increase neutrophil adhesion to human umbilical vein endothelial cell monolayers. This increase in neutrophil adhesion caused by CD66 antibodies is blocked by CD18 mAbs and is associated with upregulation of CD11/CD18 on the neutrophil surface. To examine potential interactions of CEACAMs in neutrophil signaling, the effects on neutrophil adhesion to human umbilical vein endothelial cells of a set of CD66 mAbs was tested following desensitization to stimulation by various combinations of these mAbs. Addition of a CD66 mAb in the absence of calcium results in desensitization of neutrophils to stimulation by that CD66 mAb. The current data show that desensitization of neutrophils to any two CEACAMs results in selective desensitization to those two CEACAMs, while the cells remain responsive to the other two neutrophil CEACAMs. In addition, cells desensitized to CEACAM-3, -6, and -8 were still responsive to stimulation of CEACAM1 by CD66a mAbs. In contrast, desensitization of cells to CEACAM1 and any two of the other CEACAMs left the cells unresponsive to all CD66 mAbs. Cells desensitized to any combination of CEACAMs remained responsive to the unrelated control protein CD63. Thus, while there is significant independence of the four neutrophil CEACAMs in signaling, CEACAM1 appears to play a unique role among the neutrophil CEACAMs. A model in which CEACAMs dimerize to form signaling complexes could accommodate the observations. Similar interactions may occur in other cells expressing CEACAMs

Levels of soluble FcγRIII correlate with disease severity in sepsis

Neutrophil activation is thought to play a crucial role in the pathogenesis of sepsis. During activation, neutrophils adhere to and migrate through the endothelium. Therefore, the amount of circulating neutrophils does not adequately reflect the total amount of neutrophils that are involved in the pathophysiologic process of this condition. In this study we test the hypothesis that the severity of sepsis is associated with the total body mass of neutrophils as reflected in the plasma concentration of soluble Fcγ receptor type III (sFcγRIII). Nineteen patients with sepsis (12 male, seven female, median age of 69 years, range 29–87 years) were included in this study. Ten healthy volunteers served as controls. Plasma sFcγRIII concentrations were measured by ELISA. Other parameters that were studied were leucocyte count, plasma concentrations of lactoferrin and soluble l-selectin, and surface expression of CD11b and CD66b on circulating neutrophils. Disease activity was measured using the Acute Physiology and Chronic Health Evaluation (APACHE) II score. Soluble FcγRIII levels were elevated in sepsis patients whereas soluble l-selectin levels were moderately decreased compared with healthy controls. Markers of cell activation were significantly increased in sepsis patients. Soluble FcγRIII correlated with disease severity as measured by the APACHE score (P < 0.05, r = 0.53), whereas the other parameters did not correlate with the APACHE score. In conclusion, this study demonstrates that soluble FcγRIII is a useful marker for disease severity in patients with sepsis

Immunotherapy Reduces Allergen-Mediated CD66b Expression and Myeloperoxidase Levels on Human Neutrophils from Allergic Patients

CD66b is a member of the carcinoembryonic antigen family, which mediates the adhesion between neutrophils and to endothelial cells. Allergen-specific immunotherapy is widely used to treat allergic diseases, and the molecular mechanisms underlying this therapy are poorly understood. The present work was undertaken to analyze A) the in vitro effect of allergens and immunotherapy on cell-surface CD66b expression of neutrophils from patients with allergic asthma and rhinitis and B) the in vivo effect of immunotherapy on cell-surface CD66b expression of neutrophils from nasal lavage fluid during the spring season. Myeloperoxidase expression and activity was also analyzed in nasal lavage fluid as a general marker of neutrophil activation. RESULTS: CD66b cell-surface expression is upregulated in vitro in response to allergens, and significantly reduced by immunotherapy (p<0.001). Myeloperoxidase activity in nasal lavage fluid was also significantly reduced by immunotherapy, as were the neutrophil cell-surface expression of CD66b and myeloperoxidase (p<0.001). Interestingly, CD66b expression was higher in neutrophils from nasal lavage fluid than those from peripheral blood, and immunotherapy reduced the number of CD66(+)MPO(+) cells in nasal lavage fluid. Thus, immunotherapy positive effects might, at least in part, be mediated by the negative regulation of the CD66b and myeloperoxidase activity in human neutrophils