Difference Between Flow Cytometry and Immunohistochemistry

The key difference between flow cytometry and immunohistochemistry is that flow cytometry is a technique that utilizes a laser beam to detect and measure physical and chemical characteristics of a population of cells or particles, while immunohistochemistry is a technique that uses monoclonal and polyclonal antibodies to detect specific antigens in tissues.

Flow cytometry and immunohistochemistry are two techniques that are used to diagnose diseases, especially cancers. Flow cytometry utilizes a laser beam to characterize the physical and chemical properties of cells. Immunohistochemistry utilizes monoclonal and polyclonal antibodies for the detection of specific antigens in tissue sections.

CONTENTS

1. Overview and Key Difference
2. What is Flow Cytometry 
3. What is Immunohistochemistry
4. Similarities Between Flow Cytometry and Immunohistochemistry
5. Side by Side Comparison – Flow Cytometry vs Immunohistochemistry in Tabular Form
6. Summary

What is Flow Cytometry?

Flow cytometry is a popular technique in cell biology. This technique detects and measures the physical and chemical characteristics of a cell population. Flow cytometry is widely used in the fields of immunology, molecular biology, bacteriology, virology, cancer biology and infectious disease monitoring. It utilizes a laser as a light source to count, sort, and profile cells in a fluid mixture. Therefore, it provides a rapid multi-parametric analysis of cells in a solution.

This technique begins with injecting a cell sample into the flow cytometer. Flow cytometer has three core systems: fluidics (a flow cell), optics (various filters, light detectors, and light source), and electronics (flow cytometer instrumentation). Prior to that, the sample should be treated with specific dyes depending on the cells being analyzed. Therefore, it utilizes a variety of fluorescent reagents such as fluorescently conjugated antibodies, DNA binding dyes, viability dyes, ion indicator dyes and fluorescent expression proteins, etc. This instrument allows the flow of one cell at a time through the laser beam. When light scatters through the cell and its components, it emits bands of different wavelengths. In this way, tens of thousands of cells can be quickly examined, and the data gathered are processed by a computer.

What is Immunohistochemistry?

Immunohistochemistry is a technique that utilizes monoclonal and polyclonal antibodies to determine the tissue distribution of an antigen of interest. It is a common technique in histopathology. It is a microscopy-based, immunostaining technique. This technique facilitates the selective identification and localization of antigens in cells of a tissue based on the specific binding with fluorescently labelled antibodies. This technique is widely used for the diagnosis of cancers since specific tumor antigens are expressed de novo or up-regulated in certain cancers. This technique is very useful in predicting therapeutic response in two important tumors, i.e. carcinoma of the breast and prostate. In addition to disease diagnosis, immunohistochemistry is used in the fields of drug development and biological research. Moreover, immunohistochemistry is useful when detecting and confirming infectious agents in tissues.

This technique requires biopsies, and they are processed into sections with a microtome, and then the sections are incubated with an appropriate antibody. The sites of binding of antigen-antibodies are visualized under light or fluorescent microscope.

What are the Similarities Between Flow Cytometry and Immunohistochemistry?

• Flow cytometry and immunohistochemistry are two techniques that use fluorescently labelled antibodies.
• Both techniques can detect antigens on the cell surface or within cells.
• Hence, both techniques allow detecting diseases, specifically infectious diseases and cancer.

What is the Difference Between Flow Cytometry and Immunohistochemistry?

Flow cytometry is a laser-based technique that detects and measures the physical and chemical characteristics of a cell population. Immunohistochemistry is a microscopy-based technique that allows selective identification and localization of antigens in cells of a tissue. So, this is the key difference between flow cytometry and immunohistochemistry. Moreover, flow cytometry uses a laser beam, while immunohistochemistry needs antibodies. Flow cytometer is the main instrument required in flow cytometry, while immunohistochemistry needs a light or fluorescent microscope.

Below is a summary of the difference between flow cytometry and immunohistochemistry in tabular form.

Summary – Flow Cytometry vs Immunohistochemistry

Flow cytometry needs a flow cytometer, while immunohistochemistry needs an ordinary or fluorescent microscope. Moreover, flow cytometry utilizes a laser beam, while immunohistochemistry utilizes monoclonal and polyclonal antibodies. In addition, the cost of immunohistochemistry is relatively low compared to flow cytometry. Thus, this is the summary of the difference between flow cytometry and immunohistochemistry. Both techniques are useful in diagnosing diseases such as cancers and infectious diseases.

Reference:

1. McKinnon, Katherine M. “Flow Cytometry: An Overview.” Current Protocols in Immunology, U.S. National Library of Medicine, 21 Feb. 2018, Available here.
2. Duraiyan, Jeyapradha, et al. “Applications of Immunohistochemistry.” Journal of Pharmacy & Bioallied Sciences, Medknow Publications & Media Pvt Ltd, Aug. 2012, Available here.

Image Courtesy:

1. “FACS-buisje” By Biol – Own work (Public Domain) via Commons Wikimedia
2. “Immunohistochemistry of the breast” By Nakos histopathology – Own work (CC BY-SA 4.0) via Commons Wikimedia