الفهرس 
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Abstract
Atopic dermatitis is a common and troublesome inflammatory skin disease, especially during childhood. For those affected and their families, this condition presents an extreme burden of personal suffering, impaired quality of life, and high direct and indirect costs. It is a heterogeneous disease, marked by chronic skin inflammation and immunological disturbances, which are characterized by accumulation of immunological cells, essentially T lymphocytes.
CD4+ T lymphocytes and particularly T helper 2 (Th2) cells have a central role in allergic inflammation, their accumulation in skin is essential for both the initiation and persistence of skin inflammation through their secreted cytokines. However, the mechanisms by which these cells accumulate within the epidermis layers of AD patients are poorly understood. Although a number of candidates, including the chemokine receptors- 4 (CCR4) have been implicated because of its preferential expression on Th2 cells.
In addition, memory CD4+ cells, particularly memory Th2 cells, are strongly involved in the pathogenesis of chronic inflammatory diseases. Though, the specific subpopulations of memory Th2 cells associated with chronic allergic disorders have not been identified due to the high heterogeneity of these cells and the limitations on the numbers of antigen-specific memory Th2 cells recoverable from tissues. However, CCR7 is a candidate marker that could help in identifying these cells.
The present study was conducted on 30 individuals who were categorized according to Hanifin and Rajka diagnostic criteria and SCORAD scale into:
group I: 20 children with atopic dermatitis.
group II: 10 age and sex matched normal children as a control group.
group I was further sub-classified into: mild, moderate and severe AD according to family history, SCORAD index. Circulating CCR4+ CD4+T cells and CCR7+CD45RO+CD4+ T cells frequencies were estimated, using flow cytometry and were correlated with IgE concentrations and different demographic, clinical and laboratory parameters.
After statistical assessment of the obtained results, we found significant increase in
circulating CCR4+CD4+ T cells percentages in AD patients (median of 1.9 %) than
control group (median of 0.10 %) (p=<0.001*). These cells percentages show also a significant direct correlation with disease severity assessed by SCORAD (p=0.017*) and a non-significant direct correlation to CRP (p=0.943) and total serum IgE levels (p=0.053).
Moreover, in our study, the percentages of CCR7+CD45RO+CD4+ T memory cells were significantly highly elevated in PBMCs of AD patients (median of 2.7 %) than control (median of 0.10 %) (p=<0.001*), with no significant difference between different SCORAD severity groups (p=0.094).
from our results, we can conclude that there is an increased frequency of CCR4+CD4+ T cells and CCR7+ CD45RO+ CD4+ T memory cells in peripheral blood of AD children, which are directly correlated to each other’s. This may indicate their emerging role in the pathogenesis of atopic dermatitis. Also, CCR7+CD45RO+ CD4+
memory T cells were positively correlated to white blood cells that may reflect the role of these memory T cells in the persistence of chronic inflammation in AD patients.
The percentage of CCR4+CD4+ T cells and CCR7+CD45RO+CD4+ T cells might have an important role in chronic AD patients, and specific blockade of the responses elicited by chemokines and chemokine receptors responsible for the pathological migration of these cells could therefore be of great therapeutic interest for the treatment of AD.
This study demonstrates that particular factors were the best fit for children with AD. Age at onset, age at diagnosis, white blood cells specifically, immune cells and their chemokines and chemokine receptors, in addition to C-reactive protein and serum total IgE level were the most influential factors that helped distinguish each cluster. These results support the heterogeneity of AD, even in early childhood, and define more homogeneous subtypes of AD.