Sodium citrate antigen repair solution (50×) has the ability to repair the protein crosslinking caused by fixed liquid such as paraformaldehyde. Whether it is paraffin, frozen section or cell crawl, as long as the sample is fixed with paraformaldehyde, formaldehyde or other aldehyde reagents, the antigen repair will effectively remove the cross-linking between proteins, fully expose the antigen epitope, and greatly improve the immunostaining effect. Procedure: 1. Before the reagent is ready to use, the sodium citrate antigen repair solution (50×) must be diluted with distilled water or ultra-pure water, and the antigen repair solution (1×) must be prepared. 2. Antigen Repair 2.1 For paraffin sections: 2.1.1 Dewaxing: Sections are dewaxed in xylene for 2×5min. Anhydrous ethanol 2×5min. 90% ethanol 2×5min, 70% ethanol 5min. Distilled water 2×5min. 2.1.2 Antigen repair: The section is immersed in antigen repair solution (1×) and heated at 95-100°C for about 10~30min(the best heating time should be determined according to different samples and target proteins). Note: Antigen repair solution (1×) should be preheated to 95-100°C before use. Heat can be done in a water bath or microwave. If using microwave oven heating, pay attention to avoid the repair solution boiling. Then cool to room temperature in about 20 to 30 minutes. Wash with immunostaining detergent 1~2 times, 3~5min each time. Subsequent immunostaining steps such as blocking can be performed. 2.2 Frozen section: The section was washed with immunostaining detergent for 5min. The process of antigen repair such as the process of antigen repair in paraffin sections. 2.3 The antigen repair of other samples can be carried out by referring to the steps of paraffin section. Tips: For your own safety, please take good protection before using the reagent, such as wearing a lab coat, wearing gloves, etc.