Endogenous biotin: Biotin is a kind of vitamin and participates in carboxylation as a coenzyme. In human tissues, the vast majority of biotin is related to mitochondrial pyruvate carboxylase. Therefore, mitochondrial-rich cells are rich in endogenous biotin, such as kidney, liver, and some tumor cells. If a biotin / albumin detection system is used, since the avidin can strongly bind to biotin irreversibly, it will inevitably cause non-specific staining. Heat-mediated antigen repair can significantly "resurrect" endogenous biotin, so this is exacerbated by Non-specific background staining. In addition to changing to a non-biotin detection system, the following simple method can also be used to block endogenous biotin. First, endogenous biotin was blocked with egg white in egg white (one egg white was added to 100ml of PBS), and then 5% milk powder was used as a biotin substitute (5g of milk powder was added to 100ml of PBS / TBS) to block egg white. The unbound sites in the element can be added with primary antibody after washing. Endogenous peroxidase Tianjiudi Generally, the peroxidase content in red blood cells and neutrophils is relatively high, which will cause non-specific staining. Inactivation method of endogenous peroxidase: 0.3% -3% H2O2, prepared with PBS (pH7.4) or distilled water or methanol. Flushing step The immunohistochemical staining step includes multiple flushing processes. If any step is not cleaned, background staining may occur. The solution is to add Tween 20 to the rinsing solution. Generally, add 0.2 ml of Tween 20 to the 1000ml rinsing solution. Mouse monoclonal antibody is used in mouse tissue. Because mouse tissue may contain endogenous IgG, the detection system will recognize these antibodies, resulting in non-specific staining. The solution is to either block the endogenous IgG or use a commercially available Mouse-to-Mouse test kit. Failure to fix in time can cause protein diffusion and ectopic staining. During the incubation of dry slices, if there is no wet box or too little liquid added or the incubation time is too long, local (especially edge) dry slices will be caused and should be avoided. Excessive repair of antigens (especially with EDTA) sometimes causes ectopic staining of the nucleus. For antibodies against the nucleus staining, this photo should be screened White board,Umbrella Stand,Mobile Partition,Book shelf,Magazine rack Feat Top International(China) CO.,LTD , https://www.nbfeattop.com