الفهرس 
AKNOWLEDGMENT
Sicca syndromeOnly 14 pages are availabe for public view
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Abstract
Hematopoiesis is the process of production of all types of blood cells including formation, development, and differentiation of blood cells. Prenatally, hematopoiesis occurs in the yolk sack, then in the liver, and lastly in the bone marrow.Lymphopoiesis is the production of blood cells called lymphocytes.The common lymphoid progenitor can give rise to natural killer (NK) cells, dendritic cells, and prolymphocytes.
Lymphoproliferative disorders (LPDs) refer to several conditions in which lymphocytes are produced in excessive quantities or act abnormally.LPDsare benign and malignant. Malignant of them are known as lymphoma. Lymhoma is a cancer of the immune system that affects the lymph cells which originate in the lymphatic tissues.
Lymphomas are divided into two broad categories, depending on the appearance of their cancerous (malignant) cells. These are known as Hodgkin’s lymphoma and non-Hodgkin lymphoma (NHL).There are many different types of both Hodgkin’s lymphoma and NHL.
Scientists have not yet identified what exactly makes a lymphocyte go haywire and transform into a lymphoma cell. Numerous observations implied that the pathogenesis of malignant lymphomas is multifactorial and that viruses probably play an important etiologic role. There are several examples of viruses linked to human tumours,
Hepatitis C virus causes many hepatic and extra hepatic diseases manifestations and is considered as a possible factor in the pathogenesis of lymphoproliferativediseases.Some observations have shown that anti-viral treatment appears to be effective in eliminating the clonal proliferation of B cells in patients with chronic HCV infection and treatment of HCV-associated cryoglobulinaemia
It is likely that different pathogenetic mechanisms operate in these different types of lymphomas associated with HCV infection.The first of these mechanisms is chronic antigenic stimulation This suggests that lymphomagenesis occurs when B cells proliferate in response to antigen. A second potentially lymphomagenic mechanism of HCV infection derives from the high-affinity interaction between HCV-E2 and one of its receptors, the tetraspanin CD81 and The third tumorigenic mechanism of HCV that has been proposed is direct infection of B cells .
HBV antigens can also induce chronic antigenic stimulation (CAS). Infection, integration, and CAS are proposed to be causally linked to lymphomagenesis in concurrence to other as yet undefined risk factors.