CTLA-4 Gene Polymorphisms inBronchial Asthma

BY: Ahmed Mohsen Abd al-Rahman Faheem

Demonstrator of Medical BiochemistryMansoura Faculty of Medicine

Supervisors Prof. Dr. Souad Mohamed Aboazma Professor of Medical Biochemistry Mansoura Faculty of Medicine

Dr. Ayman Zaky El-samanoudy Dr. Naglaa Mokhtar ElsherbinyAssistant Professor of Medical Biochemistry Lecturer of Medical Biochemistry Mansoura Faculty of Medicine Mansoura Faculty of Medicine

The Main Supervisor Prof. Dr. Souad Mohamed Aboazma Professor of Medical Biochemistry Mansoura Faculty of Medicine 2013

Introduction

Asthma is now the most common chronic medical illness of children and one of the most common of adult diseases (Grunig et al., 2012).

The prevalence of asthma has increased significantly over the past 20 to 30 years

The reasons for this increase remain unclear, although it may be related to immunization, diet, or parasitic and viral infection, as well as to exposure to allergens, pollutants, or endotoxins. These potential causes act directly on the immune system or end organs to initiate and aggravate sensitization and disease (Hussein et al., 2011).

Asthma is a chronic inflammatory disorder of the airways characterized by variable airflow obstruction and bronchial hyperresponsivenes (BHR).

The pathogenesis and etiology of asthma are very complex and not fully understood, although an interaction of a variety of environmental factors and multiple genetic loci polymorphisms have been suggested as important determinants (Sohn et al., 2007).

An increasing number of chromosomal regions have shown evidence of linkage to atopic traits. One such region is on chromosome 2q32-33, harboring the candidate gene cytotoxic T-lymphocyte antigen 4 (CTLA-4) (Koppelman et al., 2002).

CTLA-4 molecule is a surface molecule on activated T cells. It has a central role as a negative costimulator in Tcell regulation and together with the surface molecule CD28 modifies both activation and differentiation of T cells when stimulated by antigen presenting cells (Bour-Jordan et al., 2003).

CTLA-4 is expressed only on activated T-cells; it binds to B7 molecules on antigen-presenting cells. CTLA-4-B7 binding delivers negative signals to the T cell, affecting T cell proliferation, cytokine production and immune responses. Breakdown in the B7-CD28/CTLA-4 pathway may alter T-cell response leading to immune-mediated diseases (Sohn et al., 2007).

Aim of the work

The main aim of the current study is to explore the relation between different CTLA-4 gene polymorphisms and serum IgE in bronchial asthma (atopic and non atopic)

Subjects and methods

This study will be carried out in the department of medical biochemistry, Faculty of medicine, Mansoura university. Patients and controls will be selected from the inpatients and outpatients clinics of thoracic medicine department, Mansoura University Hospital.

All participating individuals will be subjected to the following: 1- Thorough history taking (dyspnea, cough and chest wheeze)2- Clinical examination: with especial stress on local examination of the chest.3- Pulmonary function tests (FEV, FEV/FVC ratio)4-Skin prick test will performed for asthmatic patients to differentiate between atopic and non-atopic patients.

Diagnosed patients with bronchial asthma will be furtherly classified according to the result of skin prick test into the following subgroups:

Ia : Atopic patientsIb : Non atopic patients

Age and sex matched healthy subjects will be considered as control group

Sampling:

10 ml fasting blood will be withdrawn from all individuals of the present study by vein puncture. 5 ml on K2 EDTA used for DNA extraction preserved at temperature -20 until used.

Another 5 ml will be allowed for clotting (15 minutes) then will be centrifuged (7000 rpm) for serum preparation and preserved until used for other biochemical investigations.

Biochemical investigations:

1- Measurement of serum IgE by ELIZA

2- DNA extraction, Polymerase chain reaction and determination of CTLA-4 gene polymorphism as following: Genotyping of A/G single nucleotide polymorphism at position 49 in Exon 1 using restriction enzyme BbvI Genotyping of C/T single nucleotide polymorphism at position 60 in the 3' untranslated region using restriction enzyme HpyCH4IV

References

Bour-Jordan H, Grogan JL, Tang Q, Auger JA, Locksley RM, Bluestone JA. (2003): CTLA-4 regulates the requirement for cytokine-induced signals inT(H)2 lineage commitment. Nat Immunol; 4:182-8.Grunig G, Corry D B, Reibman J, Wills-Karp M (2012): Interleukin 13 and the evolution of asthma therapy. Am J Clin Exp Immunol;1(1):20-27.Heinzmann A, Plesnar C, Kuehr J, Forster J, Deichmann KA. (2000): Common polymorphisms in the CTLA-4 and CD28 genes at 2q33 are notassociated with asthma or atopy. Eur J Immunogenet;27:57-61.Hussein Y M, Ahmad AS, Ibrahem MM, Elsherbeny HM, Shalaby SM, El-Shal AS, Sabbah NA (2011): Interleukin 13 Receptors as BiochemicalMarkers in Atopic Patients. J Investig Allergol Clin Immunol; Vol. 21(2): 101-107.

Koppelman GH, Stine OC, Xu J, Howard TD, Zheng SL, Kauffman HF,et al.(2002): Genome-wide search for atopy susceptibility genes in Dutch families with asthma. J Allergy Clin Immunol;109:498-506.Lee SY, Lee YH, Shin C, Shim JJ, Kang KH, Yoo SH, et al.(2002): Association of asthma severity and bronchial hyperresponsiveness with a polymorphism in the cytotoxic T-lymphocyte antigen-4 gene. Chest;122:171-6.Sohn M.H, Kim S-H, Song T-W, Kim K-W, Kim E-S, Park H-S, Kim K-E(2007): Cytotoxic T Lymphocyte-Associated Antigen-4 GenePolymorphisms Confer Susceptibility to Atopic Asthma in Korean Children. Pediatric Pulmonology 42:542547.Yang KD, Liu CA, Chang JC, Chuang H, Ou CY, Hsu TY, et al.( 2004):Polymorphism of the immune-braking gene CTLA-4 (+49) involved ingender discrepancy of serum total IgE levels and allergic diseases. ClinExp Allergy;34:32-7.

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