Staphylococcus epidermidis - virulence factors and innate ... - Munin

Specific aspects in neonates
There is both a qualitative and quantitative impairment of the cellular response in neonates. A
diminished precursor storage pool of both neutrophils and monocytes in the neonatal blood, and a
reduced ability of the bone marrow of the newborn child to efficiently up-regulate the production
of leukocytes during an inflammation cause a quantitative defect in the cellular innate immune
response (201-204). There are also several qualitative impairments of neutrophils, such as
deficiencies in the ability to accumulate leukocytes at the site of the infection (reduced
chemotaxis, rolling, adhesion and transmigration) (204-208), reduced expression and function of
surface molecules (such as CR2 and L-selectin) (209, 210), and reduced microbiocidal function
(such as reduced up-regulation of oxidative burst) (206, 207, 211, 212). Neonatal neutrophils also
respond differently to G-CSF and CM-CSF compared to adults. This may be of importance when
considering treatment with CSF to improve the immune function of preterm infants (213). They
also display different responses to other stimuli, such as hyporesponsivenes to LPS stimulation,
maybe due to failure of TLR-4 up-regulation (214).
Macrophages do not have reduced phagocytic and intracellular killing capacity in term infants,
but their capacity to further amplify the signal and activate the adaptive immune system seems to
be diminished (215, 216).
1.2.5 Effector - Cytokines
Cytokines are small proteins synthesized and secreted from a variety of immune cells (e.g.
monocytes, lymphocytes, neutrophils) and non-immune cells (e.g. endothelial cells) (217, 218).
Cytokine production/secretion is most often mediated by binding of an agonist to a TLR (197) or
other PRRs. This leads to transmission of signals through intracellular messenger systems,
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