For PD-L1 antibody immunohistochemistry in mouse tumors, which clone and retrieval conditions are recommended?

High background is not necessarily a problem with the antibody itself; endogenous peroxidase and melanin in B16F10 can both interfere. I recommend 3% H2O2 at room temperature for 15 minutes; for blocking, use 5% goat serum plus 1% BSA at room temperature for 1 hour, do not skip this step; for the secondary antibody, choose a polymer-based method such as EnVision, and avoid the streptavidin-biotin system; use 0.05% Tween-20 TBS as the wash buffer, and after incubation wash 3 times for 5 minutes each. For the primary antibody, I usually incubate overnight at 4°C, and the background is generally lower than with 1 hour at 37°C. Add an isotype control and a blank control for each round, and perform gradient dilutions of the primary antibody at 3 concentrations to assess background.

In terms of channels, 10F.9G2 from domestic BioLegend-authorized distributors such as Dakewe and Sizhengbo often has stock or a 1-2 week lead time; Abcam Shanghai stock is also relatively fast, and Thermo MIH5 can be purchased through Thermo Fisher or UNIV. Within your budget, buying the 100 μL small size is enough for 20 sections, and at a 1:200 dilution there will be plenty left over. Before ordering, require the distributor to provide the COA, lot number, and lead time, and try to choose the same lot to avoid affecting quantification due to a mid-course lot change. Do not use unknown channels; counterfeit or inconsistently aliquoted immunohistochemistry antibodies will waste even more sections.

I recommend trying 10F.9G2 first, available from both BioLegend and Abcam, as it gives relatively clean membrane localization on B16F10 paraffin sections; MIH5 can be used as an alternative. For antigen retrieval, I prefer EDTA pH9.0 heat retrieval for 15 minutes; citric acid pH6.0 does not provide sufficient signal for some lots compared with EDTA. For dilution, start 10F.9G2 at 1:200, and test MIH5 from 1:100 to 1:300. B16F10 has heavy melanin, which easily interferes with DAB development; if quantification is needed, consider switching to a magenta or blue chromogen, or perform color deconvolution.

For subsequent quantitative analysis, it is recommended to first perform antibody linearity validation: stain serial sections at 1:200, 1:400, and 1:800, and compare the positive ratio and background. Melanin in B16F10 will interfere with brightfield quantification; it is recommended to use QuPath for color deconvolution or use a fluorescent secondary antibody. H-score is more stable than positive area alone; select 3-5 discontinuous tumor regions per section, avoiding necrosis and edges. It is best to stain all 20 slides in one batch rather than splitting them across multiple batches; keep the chromogenic development time fixed. Add an isotype control to establish the threshold.