الفهرس 
Vitamin DOnly 14 pages are availabe for public view
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Abstract
Vitamin D has two forms: the inactive form 25(OH) D which is the main circulating form that undergoes hydroxylation in the kidney under the influence of 1α-hydroxylase enzyme to yield the biologically active form 1, 25(OH)2D. Vitamin D plays a primary physiological role in maintaining extracellular calcium ion levels in the human body, primarily by controlling the absorption of calcium from the intestine, through direct effects on bone and also through its effects on PTH secretion.
Vitamin D has an important role in both innate and adaptive immune responses as receptors for vitamin D are present in various immune cells, including monocytes, macrophages and dendritic cells, as well as T and B lymphocytes. Vitamin D exerts an inhibitory action on the immune system. In the adaptive immune system, 1, 25(OH)2 D suppresses proliferation of B cells and immunoglobulin production and retards the differentiation of B cell precursors into plasma cells. It also inhibits T cell proliferation, in particular the Th1 cells capable of producing IFN-γ and IL-2. These actions prevent further antigen presentation and recruitment of T lymphocytes (role of IFN-γ), and T lymphocyte proliferation (role of IL-2). In contrast IL-4, IL-5, and IL-10 production can be increased, shifting the balance to a Th2 cell.
Methods
All subjects in the study were subjected to the following:
1. History taking laying stress on residence, occupation, sun exposure and previous intake of vitamin D or treatment.
2. Laboratory investigations:
• Assessment of Serum 25(OH) vitamin D level using enzyme immunoassay kit (Immunodiagnostic, Mainzer Landstrasse 49 60329 Frankfurt, Germany).
• Serum PTH level by Electrochemiluminescence approach using cobas e 411 analyzer (Roche Diagnostics, Germany).
• Serum calcium level, creatinine, AST and ALT using Beckman Synchron CX9 ALX Chemistry analyzer (Diamond Diagnostics, USA).
• Peripheral blood mononuclear cell separation, stimulation by Phytohemagglutin (PHA) and culture in absence and presence of vitamin D in culture (Jing et al., 2013, with minor modifications).
• IL-10 assessment in culture supernatant in absence and presence of vitamin D in culture using enzyme-linked immunosorbent assay (ELISA) kit (Wkea med supplies, 206 No.6 Building, Chenguang Gardon, Qianjian Street, Chaoyang District, Changchun 130012, China).
Results
The present study demonstrated a high prevalence of low vitamin D status among the study group (80% of our study candidates) ranged from 5 to 65 ng/ml with 21.32 mean±14.98 2SD. Moreover, it defined some risk factors for hypovitaminos D as working indoors and absence of outdoor activities (60% of our study candidates). It also showed a high significant differences in the supernatant IL-10 levels between cultures in absence and presence of vitamin D. Also, there was significant negative correlation between sufficient serum 25(OH) D levels group and IL-10 levels in culture supernatant pretreated with vitamin D. There was significant negative correlation between serum 25(OH) D and PTH levels. On contrast, it revealed no significant correlation between serum 25(OH) D levels and age, sex and serum calcium levels.
Key words: Vitamin D, IL10: interleukin 10, DC: denteritic cells, ELISA: Enzyme-linked immunosorbent assay, T-reg: T-regulatory lymphocytes, VDR: vitamin D receptor .