预期应用
ELISA法定量测定人血清、血浆或其它相关液体中sCD28含量。
实验原理
本试剂盒应用双抗体夹心酶标免疫分析法测定标本中sCD28水平。用纯化的抗体包被微孔板，制成固相抗体，往包被单抗的微孔中依次加入sCD28抗原、生物素化的抗人sCD28抗体、HRP标记的亲和素，经过彻底洗涤后用底物TMB显色。TMB在过氧化物酶的催化下转化成蓝色，并在酸的作用下转化成最终的黄色。颜色的深浅和样品中的sCD28呈正相关。用酶标仪在450nm波长下测定吸光度（OD值），计算样品浓度。
Intended use
This immunoassay kit allows for the specific measurement of human sCD28 concentrations in serum and plasma.
Introduction
The cluster of differentiation (CD) antigen CD28 is a 44kDa, disulphide-bonded, homodimeric glycoprotein, which is constitutively expressed on the surface of the majority of T-cells.
CD28 is structurally very closely related to another molecule expressed in activated T-cells, CTLA-4. In particular, the hinge region is completely conserved for both molecules. Also CTLA-4 and CD28 were shown to be very similar at the message and at the gene structure level. The corresponding genes co-map on human chromosome 2q33.
Ligation of CD28 by its counter receptor, B7, expressed on the surface of antigen presenting cells, has been shown to induce signals that, in synergy with those derived from engagement of the T-cell receptor by an antigen bound to a major histocompatibilty complex, enhance proliferation and cytokine production. Manipulation of this interaction can have dramatic effects on the outcome of T-cell activation. Considerable research has been done on the CD28/B7 costimulatory pathway. Blocking thereof results in immunosuppression with implications for the treatment of autoimmune diseases, allergy, organ transplantation and graft versus host disease.
Activating the CD28/B7 pathway could be useful for including the immune system to recognize and eliminate tumors that evade the immune system
Test principle
This assay employs the quantitative sandwich enzyme immunoassay technique. A monoclonal antibody specific for sCD28 has been pre-coated onto a microplate. Standards and samples are pipetted into the wells and any sCD28 present is bound by the immobilized antibody. An enzyme-linked monoclonal antibody specific for sCD28 is added to the wells. Following a wash to remove any unbound antibody-enzyme reagent, a substrate solution is added to the wells and color develops in proportion to the amount of sCD28 bound in the initial step. The color development is stopped and the intensity of the color is measured.
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