fa عمومى General پژوهشي Research One of the most common leukemia in the world is chronic lymphocytic leukemia (CLL). CLL, as an incurable malignant disorder of B-lymphocytes. CD200, formerly known as OX-2, is a type I glycoprotein that is expressed on a variety of cell types. CD200 plays a vital role in the modulation of the immune system and is upregulated on the surface of numerous tumors, including chronic lymphocytic leukemia. In several studies, it is noted that CD200 was upregulated 1.6- to 5.4-fold in B cells from all patients with B-CLL and may suggest that CD200 upregulation is an early event in the B-CLL disease process. It might conclude that CD200 blocking therapy may be beneficial, and several studies have proven this. We can conclude that CD200 is an excellent prognostic factor that expresses in most CLL patients, and antiCD200 therapeutic interventions can be useful. This literature review article was conducted with the purpose of role of CD200 Expression in the Diagnosis of Chronic Lymphocytic Leukemia. Chronic Lymphocytic Leukemia, Prognosis, CD200, diagnosis 16 22 http://intjmi.com/browse.php?a_code=A-10-1-286&slc_lang=fa&sid=1 Mohammad Zahedi 10031947532846003230 10031947532846003230 No 1- Department of Laboratory Sciences, School of Allied Medical Science, Student Research Committee, Mazandaran University of Medical Sciences, Sari, Iran Seyedeh Saeede Kadkhodazade Khorasani 10031947532846003231 10031947532846003231 No 1- Department of Laboratory Sciences, School of Allied Medical Science, Student Research Committee, Mazandaran University of Medical Sciences, Sari, Iran. Amirreza Nasirzadeh 10031947532846003232 10031947532846003232 No 2- Student of Basic Sciences in Nursing, Student Research Committee, Gonabad University of Medical Sciences, Gonabad, Iran. Reza Abouali 10031947532846003233 10031947532846003233 No 3- Department of Laboratory Sciences, School of Allied Medical Science, Student Research Committee, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran Mahdi Abounoori 10031947532846003234 10031947532846003234 No 4- Medical Student, Student Research committee, Mazandaran University of Medical Sciences, Sari, Iran Parham Mortazavi 10031947532846003235 10031947532846003235 No 5- School of pharmacy, Student Research Committee, Mazandaran University of Medical Sciences, Sari, Iran. Reza Sadeghnezhad 10031947532846003236 10031947532846003236 No 6- Environmental Health Engineering, student research committee, Faculty of Health, Health Sciences Research, Mazandaran University of Medical Sciences, Sari, Iran. Ali Reza Mohseni 10031947532846003237 10031947532846003237 Yes 7- Thalassemia Research Center, Hemoglobinopathy institute, Mazandaran University of Medical Sciences, Sari, Iran