Common Issues, Cause Analysis, and Solutions in Immunohistochemical Staining Techniques
| Frequently Asked Questions | Cause Analysis | Solutions | |
| Negative Staining | Positive control staining is valid, but the test tissue shows negative staining. | The target antigen is absent in the test tissue. | Handle as a negative staining result; no need to repeat the experiment. |
| Positive control staining is invalid, and the test tissue shows negative staining. | Improper antigen retrieval operation. For example: ① Antigen retrieval is not recommended, but antigen heat retrieval was performed (e.g., Maixin product RAB-0090, HBcAg); ② Antigen enzyme digestion retrieval is recommended, but antigen heat retrieval or no retrieval was performed (e.g., Maixin product MAB-0280, MOC31). | Perform correct antigen retrieval according to the method recommended in the primary antibody instruction manual. | |
| Species mismatch between the primary antibody and the secondary antibody detection system. | Select a compatible secondary antibody detection system based on the species of the primary antibody. For example, when testing human tissue specimens: if the primary antibody is mouse anti-, choose an anti-mouse or anti-mouse/rabbit secondary detection system; if the primary antibody is rabbit anti-, choose an anti-rabbit or anti-mouse/rabbit secondary detection system. | ||
| Errors occurred during experimental operation, such as omitting a reagent or incorrect reagent addition sequence. | Strictly follow the experimental method recommended in the reagent instruction manual. | ||
| For concentrated reagents, unqualified diluents may have been used. An acidic primary antibody diluent can affect the binding ability of the primary antibody to the antigen; if the secondary antibody detection system diluent contains preservatives like sodium azide, it can affect the binding ability of the detection system to the primary antibody. | Use qualified diluents for concentrated reagents. | ||
| Incorrect primary antibody selection; an antibody suitable only for frozen tissue but not for paraffin-embedded tissue was chosen. | Select a primary antibody suitable for paraffin-embedded tissue. | ||
| Primary antibody, secondary antibody detection system, or chromogenic reagent is contaminated, expired, or ineffective. | Use uncontaminated, within-expiry-date, and well-performing reagents for the experiment. | ||
| Mismatch between the secondary antibody detection system and the chromogenic reagent. | Select the corresponding chromogenic reagent based on the type of secondary antibody detection system. For example, horseradish peroxidase (HRP) detection systems can use DAB or AEC chromogenic reagents; alkaline phosphatase (AP) detection systems can use BCIP/NBT or AP/Red chromogenic reagents, etc. | ||
| Antigen content is too low. | Use a secondary antibody detection system with higher amplification effect for the experiment. | ||
| Reagent concentration is too low, too high, or incubation time and temperature are inappropriate. | Select reagents with appropriate concentrations and follow the incubation method recommended in the instruction manual. | ||
| Water-soluble chromogen staining was followed by use of alcohol-containing counterstain or dehydration with ethanol and clearing with xylene (e.g., AEC, BCIP/NBT, AP-Red chromogenic reagents). | Restain using water-soluble counterstain and mounting medium. | ||
| Weak Staining | Positive control staining is valid, but the test tissue shows weak staining. | Improper use of fixative, damaging antigens in the tissue specimen. | Refer to the primary antibody instruction manual or relevant literature, and use the recommended fixative (e.g., 10% neutral buffered formalin). |
| Antigens are damaged during tissue processing such as fixation and embedding. | Fix fresh tissue promptly to prevent autolysis; choose an appropriate fixative with proper fixation time; use low-melting point soft paraffin (around 58°C) for embedding, with embedding temperature not exceeding 60°C. | ||
| Baking temperature too high or time too long. | Baking temperature should be 3-5°C above the melting point of the embedding paraffin (or 65-70°C), with baking time of 1-2 hours. | ||
| Low antigen content in the test tissue. | Use a secondary antibody detection system with higher amplification effect for the experiment. | ||
| Both positive control and test tissue show weak staining. | Incorrect or omitted antigen retrieval. For example, retrieval time, temperature, or pH of retrieval buffer did not meet requirements, or antigen retrieval was required but not performed. | Perform antigen retrieval according to the method recommended in the primary antibody instruction manual. Ensure correct retrieval process: retrieval temperature and time meet requirements, and appropriate retrieval buffer is used. | |
| Peroxidase blocking reagent or serum blocking time too long, or reagent concentration inappropriate. | Use commercially available ready-to-use reagents and follow the incubation method recommended in the instruction manual. | ||
| Primary antibody, secondary antibody detection system, or chromogenic reagent concentration too high or too low, or incubation time too short. | Adjust reagent concentration or use commercially available ready-to-use reagents and follow the incubation method recommended in the instruction manual. | ||
| Use of expired reagents. | Use well-performing reagents within their expiry date for the experiment. | ||
| Incubation temperature too low (below 15°C). | Extend incubation time; or incubate in a 37°C incubator, but shorten incubation time (30 minutes). | ||
| Excessive residual buffer (or serum) on the tissue when adding reagents, causing dilution of added reagents. | Remove buffer (or serum) from the tissue before each reagent addition, but avoid drying of the tissue. | ||
| Over-counterstaining. | Counterstain lightly for nuclei (different hematoxylin formulations require different staining times; optimize staining time). | ||
| Reuse of antigen retrieval buffer (may alter pH or introduce impurities, affecting antigen retrieval efficacy). | Use freshly prepared antigen retrieval buffer each time, adjusting its pH to the required range. | ||
| Chromogenic reagent incubation time too short or incorrect reagent preparation (e.g., inappropriate hydrogen peroxide concentration or excessive chromogen when preparing DAB). | Prepare chromogenic reagents strictly according to the method recommended in the instruction manual; if possible, observe and control staining time under a microscope. | ||
| Positive control staining is valid, but the test tissue shows “yin-yang face” staining. | Reagent did not completely cover the tissue when added. | After each reagent addition, carefully check to ensure the reagent completely covers the tissue. | |
| Uneven experimental bench or incubation box, causing the slide to tilt; added reagent flows to the lower side, leaving the other side uncovered or with little reagent, resulting in “yin-yang face” staining. | Ensure the experimental bench and incubation box are level during the experiment. | ||
| Bubbles present when adding reagent to the tissue and not removed. | After adding reagent, check carefully; if bubbles are present, be sure to remove them. | ||
| Insufficient tissue fixation time, leading to inadequate fixation in the central area. | Tissue fixation time should meet standard requirements. | ||
| Background Staining | Background staining in control and test tissues, or in tissue components like fat, connective tissue, and epithelium. | Incomplete slide deparaffinization. | Use fresh xylene or its substitutes for deparaffinization. |
| Over-retrieval of antigens. | Strictly control antigen retrieval time and temperature; follow the method recommended in the primary antibody instruction manual or develop a more suitable retrieval method for your own laboratory. | ||
| Primary antibody concentration too high, incubation time too long, or incubation temperature too high. | Reduce primary antibody concentration, shorten incubation time, control incubation temperature. Typical primary antibody incubation conditions: room temperature for 1h, 4°C overnight, or 37°C for 30min (adjust according to laboratory conditions). | ||
| Secondary antibody detection system concentration too high, incubation time too long, or incubation temperature too high. | Reduce reagent concentration and follow the incubation method recommended in the reagent instruction manual. | ||
| Chromogenic reagent incubation time too long. | Shorten chromogenic reagent incubation time; preferably observe and control staining time under a microscope. | ||
| PBS buffer reused multiple times or insufficient slide washing. | Use fresh PBS buffer each time; ensure thorough slide washing; Tween-20 at 0.025-0.05% can be added to the buffer. | ||
| Use of incorrect blocking serum. | Blocking serum should generally be of the same species as the secondary antibody detection system, or use serum-free protein block; do not use serum from the same species as the primary antibody. | ||
| Adhesive on the slide is too thick. | Re-prepare adhesive and make new adhesive-coated slides. | ||
| Background staining in test tissue and negative reagent control, while positive and negative tissue controls stain validly. | Delayed tissue fixation, causing antigen diffusion and retention within the tissue. | Fix tissue promptly. | |
| During tissue collection, use of a dull blade causes tissue compression and deformation, leading to serum protein diffusion and retention within the tissue. | Use a sharp blade for tissue collection. | ||
| Test tissue has areas of necrosis, damage, or compression. | Ignore these physically damaged areas when observing staining results or re-collect tissue. | ||
| Tissue section too thick. | Formalin-fixed, paraffin-embedded tissue sections are typically 3-5μm thick; frozen sections should not exceed 10μm. | ||
| Negative reagent control is invalid, while positive and negative tissue controls and test tissue stain validly. | Negative control serum concentration inappropriate. | Use negative control serum at appropriate concentration. For monoclonal antibodies, dilute negative control serum so its IgG content is similar to the primary antibody; for polyclonal antibodies, dilute so its protein content is similar to the primary antibody. | |
| Negative control serum is contaminated and cross-reacts with proteins in the test tissue. | Use uncontaminated negative control serum for the experiment. | ||
| Control staining is valid, but test tissue shows focal background staining. | During mounting, water not fully drained, forming bubbles causing tissue protrusion; reagents seep into this area during the experiment and are difficult to wash off, leading to over-staining. | Ensure water is fully drained during mounting. | |
| Water in the water bath used for mounting is contaminated with bacteria or yeast. | Regularly clean the water bath and ensure clean water is used each time. | ||
| When preparing APES-coated slides, APES concentration too high, leaving white spots after drying; these spots stain during chromogenic reaction. | Prepare adhesive-coated slides strictly according to the method recommended in the reagent instruction manual. | ||
| Tissue sections have folds, tears, knife marks, etc., preventing thorough washing of reagents during the experiment, leading to over-staining. | Ensure test tissue sections are intact, without folds, tears, knife marks, etc. | ||
| Control staining is valid, but test tissue shows edge effect. | Tissue edges not firmly adhered to the slide; after antigen heat retrieval or subsequent buffer washes, edge tissue loosens and floats, making it difficult to wash reagents beneath during each wash, leading to over-staining in this area. | Standardize tissue pre-processing (especially dehydration), ensure section thickness is appropriate, use slides with good adhesive properties, and avoid direct washing onto the tissue. | |
| When adding reagent, it does not fully cover the tissue, leaving edges with little or no reagent; during incubation, this area dries first, causing higher concentration than central tissue and resulting in over-staining. | Ensure reagent fully covers the tissue each time (you can draw a circle 3mm from the tissue edge with an immunohistochemistry pen before adding reagent). | ||
| Control staining is valid, but test tissue shows non-specific nuclear staining. | Inappropriate tissue pre-processing, such as prolonged immersion in xylene, improper fixative use; tissue drying, incorrect pH or time of antigen retrieval buffer, or excessive evaporation during retrieval leaving part of tissue unimmersed. | Strictly follow standard operating procedures. | |
| When using a biotin-based secondary antibody detection system, endogenous biotin in tissue causes staining. | This non-specific staining often occurs in high-metabolism organ tissues. After antigen heat retrieval, endogenous biotin in tissue links with streptavidin-peroxidase in the biotin detection system, causing non-specific staining, mostly localized in cytoplasm and highly misleading. | Use endogenous biotin blocking reagent for blocking; or use non-biotin detection systems, such as Maixin’s MaxVisionTM, MaxVisionTM 2, EliVisionTM plus, EliVisionTM Super. | |
| When using horseradish peroxidase (HRP) secondary antibody detection system, endogenous peroxidase in tissue causes staining. | This staining often occurs in red blood cells, necrotic tissue, and inflammatory cells, due to incomplete or absent blocking of endogenous peroxidase with appropriate blocking reagent. | Use peroxidase blocking reagent, appropriately extend blocking time; or use alkaline phosphatase (AP) detection system. | |
| Tissue Detachment | Inappropriate tissue processing and paraffin block selection. | Follow “Clinical Technical Operation Specifications – Pathology Volume” for tissue processing, ensure thorough dehydration, and avoid tissues with high fat content when possible. | |
| Poor adhesive properties of the slide. | Use slides with good adhesive properties. | ||
| Incorrect antigen retrieval, such as over-retrieval or rapid cooling after retrieval. | Perform correct antigen retrieval according to the method recommended in the primary antibody instruction manual. | ||
| Tissue sections too thick, uneven, folded, etc. | Tissue section thickness should be 3-5μm, sections should be complete, uniform, and without folds. | ||
| Baking conditions: temperature too low, time too short, etc. | Baking temperature should be 3-5°C above the melting point of the embedding paraffin (or 65-70°C), with baking time of 1-2 hours. | ||
| Incorrect washing method, such as washing directly onto the tissue. | Master the correct washing method. | ||