Antigen overload

Packed Red Blood Cells Contain all blood products except plasma and are used to decrease circulatory overload and reduce the risk of reactions to antigens contained in plasma... 

Hereditary hemochromatosis is a common condition of spontaneous iron overload. It is a human leukocyte antigen (HLA)-linked, autosomal recessive disorder affect-... 

Serial studies of lymphocyte populations in HH patients being phlebotomized showed that abnormally low numbers of lymphocytes, particularly T CD8-f lymphocytes, were associated with a more severe iron overload (reviewed in [16]). These observations led to the discovery in 1994 of spontaneous iron overload in knock-out mice lacking expression of pi microglobulin and consequently expression of major histocompatibility complex (MHC) class I antigens and CD8-I- cells [17]. 

The precise mechanism(s) by which a non-classical MHC class I antigen or T lymphocytes can influence iron homeostasis remain(s) elusive. Recently it has been shown that the wild-type HFE protein forms a stable complex with the transferrin receptor (TfR) [23-25]. That association seems to lower the afiinity of transferrin for its receptor, a finding still under dispute (W. Sly, personal communication). The mutant protein regardless of the mutation apparently fails to lower that afiSnity. This would provide the first molecular basis for the greater iron loading of the hepatic cells, but not for the lack of iron overload seen in the intestinal epithelial cells or the macrophages of HH patients. 

Blood and blood products consist of whole blood, packed red blood cells, plasma, and albumin. Whole blood consists of all cellular and plasma components of blood. Whole blood should be used to treat severe cases of anemia—not mild cases of anemia— because one unit of whole blood elevates hemoglobin by 0.5 to 1.0 g. (By comparison, a unit of packed red bloods elevates the hematocrit— percentage of semm occupied by red blood cells—by three points.) Packed red blood cells are whole blood without plasma and are used to decrease circulatory overload and to decrease the risk of reaction to antigens contained in plasma. 

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