Es (sheep erythrocytes)

Absorbance: A412 nm = 0.87 at 1/50 dilution in deionized waterGeneral DescriptionSheep red blood cells which have been washed free of sheep complement proteins, but were not coated with hemolysin antibodies. These cells have traditionally been used as negative controls for assays of the human classical and alternative complement pathways in serum samples (Morgan, B.P. (2000); Dodds, A.W. and Sim, R.B. (1997)). Most human serum samples have small amounts of natural antibodies (usually IgG) to sheep antigens and at high concentrations of serum will agglutinate Es and activate the classical pathway leading to lysis. This rarely occurs at dilutions used in the CH50 titration assay where serum is diluted more than 1/100. Es are supplied at assay-ready concentrations in the traditional buffer used in CH50 assays (GVB⁺⁺). They can usually be used for 2 weeks after preparation. They are shipped cold, but are not harmed by extended periods at room temperature (note that they circulate 60-90 days a 37℃ in vivo). They should be washed once before each use (5 min at 500 to 1000 x g at 4℃) and resuspended in GVB++ to reduce background. This procedure may also be used to concentrate the cells.Physical CharacteristicsEs are natural uncoated erythrocytes that do not activate complement under typical assays conditions. They do not have IgG or IgM on their surface, however, there are natural antibodies in most animal serum. In the most sensitive assays it has been estimated that as few as 10 IgM/EA can cause lysis while this requires approximately 1000 IgG/EA (Ross, G.D. (1986)). This is primarily because in IgM there are five closely spaced Fc domains in fixed positions on each molecule. The spacing of IgG molecules is more random and it is relatively rare to find two or more IgG in the correct positions on the surface of a cell.ApplicationsEs cells are primarily used as controls for CH50 assays and for specialized tests requiring uncoated erythrocytes. Natural antibodies present in human blood to animal antigens may cause agglutination of the cells and lysis if the serum is used at high concentrations, however, this does not interfere with the CH50 titers because EA used in these assays already carry high levels of IgM antibodies and serum is diluted 100-fold or more. IgG antibodies are 100-fold less active than IgM and most of the cross-reactive antibodies in human blood are IgG.RegulationSheep erythrocytes (Es) are used for human complement assays partly for convenience, but also because they lack membrane-bound regulators of human complement. No significant level of functional DAF, CD59 or CR1 exists on Es for human complement. Thus, Es are useful for their lack of membrane regulatory activities. Specifications and Purity: 5 x 10⁸ cells/mL. Related Document: https://ald-pub-files.oss-cn-shanghai.aliyuncs.com/aladdinsci/pdp/sds/1/E501223-SCI_26f8808def14889ca681e16fcf6ca9ed.pdf.