الفهرس 
The involvement of T lymphocytes in the pathogenesis ofOnly 14 pages are availabe for public view
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Abstract
Psoriasis is a common, genetically determined, chronic
inflammatory and hyperproliferative skin disease with no sex predilection.
The immune system has a prominent role in development of this disease. A
possible role of growth factors in the pathogenesis of psoriasis is suggested
through its effect on keratinocytes proliferation.
Growth factors are defined as polypeptides that stimulate cell
proliferation through binding to specific high affinity cell membrane
receptors present at the target cell surface by a receptor mediated
endocytosis. In healthy adults they act via paracrine mechanism, while in
neoplastic cells they act through autocrine stimulation of growth. Cells of
most tissue types are targets of growth factors, which mediate their effect via receptors with intrinsic tyrosine kinase activity.
Epidermal growth factor (EGF) is a growth factor that plays an important role
in the regulation of cell growth, proliferation, and differentiation. It also increases
cancer risk. Human EGF is a 6045-Da protein with 53 amino acid residues and three
intramolecular disulfide bonds. Epidermal growth factor (EGF) is a low molecular
weight polypeptide mitogen growth factor that increases the growth and persistence of
cells of epithelial (ectodermal) and endodermal origin in vivo and induces growth of
epithelial cells and fibroblasts in vitro, It is formed in the submaxillary gland and kidney tubules and is present in nanograms quantities in the plasma. EGF acts by
binding with high affinity to epidermal growth factor receptor (EGFR) on the cell
surface and stimulating the intrinsic protein-tyrosine kinase activity of the receptor
In this study, we measured EGF and epidermal thickness in the
lesions of psoriatic patients and in non lesional skin and for volunteers
Results were compared to evaluate its role in the pathogenesis of psoriasis.
The study was conducted on 30 cases, 20 psoriasis vulgaris
patients, and 10 healthy volunteers; all cases were subjected to complete history taking, clinical examination (including PASI score for psoriasis
patients) and skin biopsies. A 4 mm punch skin biopsies were obtained
from the lesional and non lesional skin of psoriasis, while 2 biopsies were
taken from control group from apparently healthy skin. Estimation of
tissue level of EGF was done by quantitative PCR. Epidermal thickness
was measured.
By measuring tissue level of EGF, our data revealed that EGF was
higher in lesional than in non lesional skin and the difference was
statistically significant (p<0.001). Both lesional and non lesional EGF
was higher than control group and the difference was significant
(P<0.001).
The difference of epidermal thickness was not significant
between non lesional skin and control group, while it was highly
significant between lesional and non lesional P<0.001, and between
lesional and control group P<001. Also, correlation of EGF and epidermal thickness was highly significant P<0.001.
We concluded that the elevated level of EGF in psoriatic play an
important role in pathogenesis of psoriasis possibly through its
hyperproliferative effect on keratinocytes.
In conclusion, our findings indicate that EGF serve as an important
regulator of cellular growth, proliferation and differentiation in
psoriasis, and this may show a unique patterns for specific dermatoses
and are not universally elevated in all skin diseases associated with
abnormal cellular proliferation and/or differentiation. It is not clear if
the rise in the level of EGF reflect the consequence of the disease or
the cause of the disease. Further studies to determine factors that
regulate EGF expression may yield important new insights into the
pathogenesis of specific skin diseases and this could help in generating
a spectrum of new therapeutic pattern specifically designed to target EGF or its receptors in such diseases.