What is the Difference Between Immunoprecipitation and Coimmunoprecipitation

The key difference between immunoprecipitation and coimmunoprecipitation is that immunoprecipitation is a technique that precipitates a protein out of the solution using a specific antibody, while coimmunoprecipitation is a technique that precipitates intact protein complexes out of the solution using a specific antibody.

Antigen-antibody interaction is a specific chemical interaction between antibodies produced by B cells and antigens (proteins) during an immune reaction. Normally, soluble antigens combine with soluble antibodies in the presence of an electrolyte at soluble temperature and pH in order to make an insoluble visible complex. This is called a precipitation reaction. Therefore, immunoprecipitation and coimmunoprecipitation are two types of precipitation reactions that are routinely used in labs to identify proteins such as antigens.

CONTENTS

1. Overview and Key Difference
2. What is Immunoprecipitation 
3. What is Coimmunoprecipitation
4. Similarities – Immunoprecipitation and Coimmunoprecipitation
5. Immunoprecipitation vs Coimmunoprecipitation in Tabular Form
6. Summary – Immunoprecipitation vs Coimmunoprecipitation

What is Immunoprecipitation?

Immunoprecipitation is a technique of precipitating a protein out of a solution using a specific antibody. Sometimes, this technique is also known as individual protein immunoprecipitation. Immunoprecipitation uses an antibody to isolate a selected protein of interest from cell lysate. The antibody purifies its specific target protein or antigen from a mixture. The antibody binds to the protein, and the antibody-antigen complex is pulled out of the sample. In the experimental setup, the antigen-antibody complex is pulled out using protein A/G coupled agarose or magnetic beads. Later, the beads are washed, and the protein of interest is eluted. The purified protein or antigen obtained by immunoprecipitation is verified by a variety of techniques such as enzyme-linked immunosorbent assay (ELISA) and western blot (WB).

Figure 01: Immunoprecipitation

Furthermore, isolated proteins or antigens can be quantified and identified through mass spectrometry by using enzymatic digestion patterns based on the primary sequence. There are certain considerations before starting an immunoprecipitation experiment: method format choice, binding proteins and beads, choosing the right primary antibody and isotype, and negative control.

What is Coimmunoprecipitation?

Coimmunoprecipitation is a technique of precipitating intact protein complexes out of the solution using a specific antibody. Coimmunoprecipitation generally works by selecting a specific antibody that targets a known protein (antigen) which is believed to be a member of a larger complex of proteins. By targeting the known member with a specific antibody, it is possible to pull the entire protein complex out of the solution. This enables the identification of the unknown members of the complex. The concept of pulling protein complexes out of solution is sometimes referred to as “pull-down” mechanism.

Figure 02: B Coimmunoprecipitation

Coimmunoprecipitation is a powerful technique that is used to analyze protein-protein interactions. The main purpose of coimmunoprecipitation is the identification of interacting partners such as ligands, cofactors, or signalling molecules to the protein of interest. Moreover, coimmunoprecipitation is an effective technique that is used to separate proteins from serum, cell lysate, homogenized tissue, or conditioned media.

What are the Similarities Between Immunoprecipitation and Coimmunoprecipitation?

  • Immunoprecipitation and coimmunoprecipitation are two types of precipitation reaction-based techniques.
  • Both techniques can be used to identify target antigen through a specific antibody.
  • Both techniques strongly depend on antigen-antibody interaction.
  • They are routinely used in clinical laboratories.

What is the Difference Between Immunoprecipitation and Coimmunoprecipitation?

Immunoprecipitation is a technique that precipitates a protein out of the solution using a specific antibody, while coimmunoprecipitation is a technique that precipitates intact protein complexes out of the solution using a specific antibody. Thus, this is the key difference between immunoprecipitation and coimmunoprecipitation. Furthermore, immunoprecipitation is more commonly used in laboratories, while coimmunoprecipitation is not commonly used in laboratories.

The below infographic presents the differences between immunoprecipitation and coimmunoprecipitation in tabular form for side by side comparison.

Summary – Immunoprecipitation vs Coimmunoprecipitation

Immunoprecipitation and coimmunoprecipitation are two types of precipitation reaction-based techniques that depend on antigen-antibody interaction. The immunoprecipitation technique precipitates a protein out of the solution using a specific antibody, while the coimmunoprecipitation technique precipitates intact protein complexes out of the solution using a specific antibody. So, this summarizes the difference between immunoprecipitation and coimmunoprecipitation.