Abstract
In inflammatory reactions, eosinophils and neutrophils constitute the
major classes of granulocytes that emigrate from the bloodstream into the
tissues. The recruitment of inflammatory cells constitutes a multi-step
process that includes sequential adhesion and transmigration through, the
endothelial lining, the underlying basement membrane and a variety of
extracellular matrix components. This thesis examines the adhesion and
transmigration properties of neutrophil and eosinophil during different
inflammatory processes.
We have investigated the in vitro effect of eotaxin on human peripheral
blood eosinophils (PBE) with respect to CD11b/CD18 expression and
adhesion properties to the matrix protein fibronectin. We demonstrate
that eotaxin is involved in the quantitative up-regulation of CD11b/CD1 8
expression and increases the adhesion properties in primed, but not
resting, human eosinophils. We hypothesise that eotaxin and IL-5, but not
MP, act synergistically in these respects.
The adhesion and transmigration assays were set up to simultaneous
analysis of eosinophil and neutrophil adhesion and transmigration in
mixed granulocyte cell populations, based on analysis of eosinophil
cationic protein (ECP) and myeloperoxidase (WO) as markers for
eosinophils and neutrophils, respectively. These models can be useful
tools in exploring the mechanisms whereby neutrophils and eosinophils
integrate chemotactic signals, communicate and to evaluate the impact of
this communication on the overall leukocyte accumulation at disparate
inflammatory sites.
We examined the capacity of circulating neutrophils, collected before,
during and after hemodialysis with cuprophan, low- and high-flux
polysulfone dialyzers, to transmigrate through a fibronectin covered
membrane in vitro. The high-flux polysulfone treatment, as opposed to
low-flux and cuprophan dialyzers, ameliorates the transmigration
properties of circulating neutrophils, despite similar effects on
adhesion molecule phenotypes.
Eosinophils in the neonatal period possess an enhanced responsiveness
against the bacterialrelated peptide MP, as judged by enhanced
transmigration capacity and CD11b upregulation, presumably due to the
ability to express the fMLP receptor. We therefore suggest that
eosinophils in the neonatal period represent a first line of cellular
defence that might be triggered by bacterial antigen stimulation
initiated by the early colonisation of the surfaces of the mucosa.
We demonstrate that PBE in allergic, but not in healthy children possess
an increased spontaneous, as well as eotaxin-induced capacity to
transmigrate in vitro. This increased capacity is further enhanced within
2 hours after an allergen challenge in vivo without accompanying signs of
eosinophil activation in terms of increased PBE counts or ECP levels.
These observations are probably related to the phenomenon designated
"priming".
