Red blood cell (RBC) transfusion is a common therapeutic approach, and almost 85 million packed red blood cells (pRBCs) are transfused annually worldwide.Transfusion efficacy largely depends on the patient's general health, but the composition of transfused pRBCs also can have an impact.

Red blood cell (RBC) transfusion is a common therapeutic approach, and almost 85 million packed red blood cells (pRBCs) are transfused annually worldwide.Transfusion efficacy largely depends on the patient's general health, but the composition of transfused pRBCs also can have an impact. pRBCs are prepared from donated whole blood and can be stored for up to 35 days.During storage, modifications of RBCs occur and affect product quality. Among other changes, these "storage lesions" induce microparticle (MP) formation. MPs are membrane particles measuring 0.1 to 1 µm produced by stimulated or apoptotic cells through modulation of membrane lipid organization and cytoskeleton reorganization. MPs can be produced from any cell type and express antigens characteristic of their original cell. Blood contains platelet-derived MPs (PMPs), which are the most frequent; RBC (erythrocyte)-derived MPs (ERMPs), representing 4% to 8% of total blood MPs; and, more rarely, MPs produced by endothelial cells and leukocyctes. In vivo, aging RBCs release ERMPs over their whole life cycle as a preventive effect of phagocytosis by macrophages. It seems that MPs quickly spread through the body, leading to a variety of biological effects by contact and interactions with many cells. MPs are well-known bioeffectors that mediate strong procoagulant potential, mainly because of phosphatidylserine and tissue factor expression. In this way, MPs are involved in coagulation disorders associated with atherothrombosis and cardiovascular diseases.Their ability to modulate inflammatory and immune responses is increasingly being studied as well as their capacity to carry and transport RNA, DNA, major histocompatibility complex molecules, and infectious agents. Moreover, depending on the type of stimulation that induces MP production, the size and biological functions of the MP can vary.

Inclusion Criteria:

• Donors who met criteria of Egyptian National Transfusion Services.
• Serological assays for all blood donors (HBsAgs, HCV antibodies, HIV Ag/Ab and Syphilis antibodies) on Architect i 2000 SR or Centaur XPT (chemoluminescence).

Exclusion Criteria:

• Donors who not met criteria of Egyptian National Transfusion Services.
• Reactive serology.

Group 1: 30 filtered backed RBCs. Group 2: 30 non-filtered backed RBCs.