What are Controls in Histology?
In the field of
histology, controls are essential for validating the results of staining and other diagnostic procedures. A control is a sample that is treated in the same way as the experimental samples but is known to either contain or lack the target of interest. This ensures that the staining methods and procedures are functioning correctly.
Validation: Ensures that the staining protocol is working as expected.
Comparability: Allows comparison between experimental and control samples to confirm the specificity of staining.
Consistency: Helps in maintaining consistent results across different experimental runs.
Types of Controls
There are various types of controls used in histology, each serving a different purpose: Positive Controls: These are samples known to contain the target antigen or molecule. They confirm that the staining procedure can detect the target.
Negative Controls: These are samples known to lack the target antigen or molecule. They ensure that any staining observed is specific to the target and not due to non-specific binding.
Internal Controls: These are parts of the same tissue section that are known to contain or lack the target antigen. They provide an internal comparison within the same sample.
Isotype Controls: These are used to detect non-specific binding of the primary antibody.
What is the Target of Interest?
Knowing what you are trying to detect is crucial. For instance, if you are looking for a specific protein, your positive control should be a tissue known to express that protein.
What Type of Staining is Being Used?
The type of staining, whether it is
immunohistochemistry,
immunofluorescence, or
H&E staining, will influence the choice of controls. For immunohistochemistry, you might need both positive and negative controls to validate antibody specificity.
Are There Known Variations in Expression?
Some antigens may have variable expression levels across different tissues or conditions. In such cases, having multiple controls with varying levels of expression can be beneficial.
Common Pitfalls in Control Selection
Even with the best intentions, mistakes can be made in selecting controls. Here are some common pitfalls: Over-reliance on a Single Control: Using only one type of control can be misleading. It's best to use a combination of positive and negative controls.
Inappropriate Tissue Selection: Ensure that the control tissue is relevant to the experimental samples. Using unrelated tissues can lead to incorrect conclusions.
Ignoring Batch Variability: Controls should be run with each batch of experiments to account for variability in staining procedures.
Conclusion
In summary, the selection of appropriate controls in histology is crucial for ensuring the validity and reliability of your results. By carefully considering the target of interest, the type of staining, and potential variations in expression, you can choose the right controls to make your experiments robust and reproducible. Always be mindful of common pitfalls and strive for a comprehensive approach to control selection.
