Islet cell membrane antibody

Islet cell membrane antibody (ICAS) is an autoantibody to the islet cell membrane surface antigen. It is an IgG antibody with organ specificity and not species specificity. ICAS acts on islet cell surface antigens to form antigen-antibody complexes that affect the normal function of cells. Basic Information Specialist classification: growth and development check classification: immunological examination Applicable gender: whether men and women apply fasting: not fasting Analysis results: Below normal: Normal value: no Above normal: negative: Normal: negative. Positive: Serum ICSA can be positive in patients with type 1 diabetes. Tips: Try to eat less and eat as much as possible, and arrange your diet reasonably. Normal value negative. Clinical significance Serum ICSA can be positive in patients with type 1 diabetes. Precautions Most of the insulin secreted from islet β cells is inactivated in liver and kidney, and about 40% to 50% of them are inactivated by portal vein. Therefore, liver and kidney function, especially liver function, is an important factor affecting insulin content in circulating blood. Diabetes patients often use insulin, especially animal insulin, to produce insulin antibodies in the body. Because insulin and insulin antibodies can produce a high immune response, it can affect the determination of plasma insulin. In addition, blood proinsulin, pro-proinsulin content and endocrine system diseases such as anterior pituitary, adrenal cortex, thyroid hyperthyroidism, thiazide diuretics, glucocorticoids and other drugs as well as infection, fever, surgery and other stress states It is a common factor affecting the determination of insulin. Inspection process The method is divided into three steps, namely antigen-antibody reaction, B and F separation, and radioactivity determination. (1) Reaction of antigen with antibody: The specimen (non-labeled antigen), labeled antigen and antiserum are sequentially dosed into a small test tube, and allowed to stand at room temperature (15 to 30 ° C) for 24 hours to fully compete for binding. (2) Separation of B and F: There are various separation techniques, and the precipitation method is commonly used. 1 second antibody precipitation method: also known as diabody method, after the test antigen specifically reacts with the first antibody, the corresponding second antibody is added, so that the formed antigen-first antibody-second antibody complex is co-precipitated. The labeled antigen B is separated from the free antigen F by centrifugation. This method is a specific precipitation, complete separation, low non-specific binding. However, the amount of the second antibody is large and the cost is high. In addition, the serum concentration and the presence or absence of anticoagulants can affect the results to some extent. 2 Polyethylene glycol (PEG) precipitation method: the protein is in an isoelectric point state, and the hydration layer is destroyed to cause protein precipitation. The advantage of this method is that PEG is convenient to prepare, inexpensive, and rapid to separate. The disadvantage is that there are many non-specific precipitates and the separation is incomplete. 3Second antibody-polyethylene glycol precipitation method: This method not only has the advantage of rapid precipitation of PEG method, but also maintains the effect of specific precipitation of second antibody, reduces the amount of second antibody, and reduces the concentration of PEG, so that non-specific precipitation Reduced material. 4 Activated carbon adsorption method: the free part of small molecules is adsorbed by the surface activity of activated carbon. For example, a layer of dextran is coated on the surface of the activated carbon to make a mesh having a certain pore diameter on the surface, thereby allowing small molecules of free antigen or hapten to escape and being adsorbed, while the macromolecular complex is excluded. After the antigen and the antibody are reacted, the dextran-activated carbon is added and allowed to stand for 5 to 10 minutes, so that the free antigen is adsorbed on the activated carbon particles, and the particles are precipitated by centrifugation, and the supernatant contains the labeled antigen. (3) Determination of radioactivity: After separation of B and F, the radioactivity can be measured. There are two types of measuring instruments: a liquid scintillation counter (measuring beta rays) and a crystal scintillation counter (measuring gamma rays). The unit of counting is the number of electrical pulses output by the detector in units of cpm (number of pulses/min). A standard curve is required for each measurement, and the different concentrations of the standard antigen are plotted on the abscissa, and the corresponding radioactivity measured is plotted on the ordinate. The radioactivity may be optionally B or F, and the calculated values ​​B/B+F, B/F or B/B0 may also be used. Specimens should be determined in duplicate, the average value is taken, and the corresponding antigen concentration is detected on the standard curve. Not suitable for the crowd There are no special taboos. Adverse reactions and risks There are no related complications and hazards.