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Abstract
Psoriasis is an immunologically mediated, probably autoimmune disease in which T helper type 1 cytokine play
an important role. It has been suggested that natural killer
(NK) and natural killer- T (NK-T) cells may play an important role in the pathogenesis of these diseases and
numbers of circulating NK cells are significantly reduced in these conditions.
NK cells are subpopulation of cytotoxic lymphocytes that express the activation markers CD16, CD56 and the inhibitory marker CD158a, and CD94, which can be either inhibitory or activatory depending on the ligand.
The main function of natural killer cells is to recognize and lyse virally infected cells and malignant cells, which do not express major histocompatibility complex (MHC) class 1
alleles.
NK-T cells are lymphocytes that express NK receptors but unlike NK cells also express T-cell receptors such as
CD3,T cell receptor-alpha and beta and the V beta receptors.
Narrowband UVB is an established and effective treatment for psoriasis. NB-UVB uses a special lamp (the philipis TL01 lamp). In psoriatic patients, TL-0l photo therapy lowers peripheral natural killer cell activity, lymphoproliferation and immunoregulatory cytokine production by both Th1 (IL-2. IFN-γ) and Th2 (IL,-10) T-cell populations. The PASI score has been used to give an objective quantification of severity of psoriasis after treatment with NB-UVB.
The aim of our work was to study the effect of NBUVB on natural killer T cells CD3 CD56+ in patients with
psoriasis before and after treatment.
The study included ten male patients of psoriasis and five apparently healthy males as a control group. The age of
the study subjects ranged from 20 to 35 years with a mean value of SD 25.96±5.6133.The patients and control group are matched as regard age.
Samples of peripheral blood were taken from patients with psoriasis before and after treatment with narrow band
UVB to determine the number of CD3+, CD56+ and CD3+ CD56 NK-T cells.
Our results revealed that there was a significant decrease in the number of CD3+CD56+ in the peripheral blood of patients with psoriasis and that the percentage of these cells increased after treatment with NB-UVB but
remained significantly lower than those found in healthy controls. However, there was no statistically significant
difference in the mean of CD3+ and CD56+ between psoriatic patients and controls.
On studying the severity of psoriasis before and after treatment using PASI score, there were no severe or moderate
patients after treatment, only symptomless and mild patients.
The fact that many factors are implicated in the pathogenesis of psoriasis can explain the variability in the results produced by different studies. Since we did not study
NK-T cells in the skin,we couldn’t exclude that the decrease in NK T cells in the peripheral blood might come from the differential homing of NK T cells to the skin lesions. Further studies are needed to elucidate the direct role of NK T cells in the skin of patients with psoriasis.