Quantitative aspects of immunogold labeling in embedded and in nonembedded sections

Area of Science:

• Cell Biology
• Immunocytochemistry
• Biochemistry

Background:

• Immunogold labeling in ultrathin cryosections is affected by differential immunoreagent penetration.
• This penetration difference leads to variable labeling efficiency across cell structures.
• Consequently, labeling densities in nonembedded sections are limited to measuring antigen concentration within a single cell structure.

Purpose of the Study:

• To develop a method for quantifying antigen concentration at subcellular levels.
• To overcome limitations of differential reagent penetration in immunolabeling.
• To establish a reliable in situ protein measurement technique.

Main Methods:

• Tissue embedding in 30% polyacrylamide (PAA) to equalize immunoreagent penetration.
• Utilizing immunogold labeling procedures on PAA-embedded sections.
• Comparing Ig-gold and protein A-gold for antigen detection sensitivity and specificity.

Main Results:

• Polyacrylamide embedding negated differences in labeling efficiency caused by reagent penetration.
• This equalization enabled accurate in situ protein concentration measurement at subcellular levels.
• Protein A-gold was preferred over Ig-gold due to lower nonspecific labeling and more precise antigen detection.

Conclusions:

• Polyacrylamide embedding is a crucial step for accurate quantitative immunocytochemistry.
• The developed method allows for reliable in situ measurement of protein concentrations in subcellular compartments.
• Protein A-gold offers superior performance for precise antigen detection in this quantitative immunocytochemical approach.