Serology in the Modern Lab: Techniques and Applications in Disease Detection

The constituents of our blood are important keys to assessing our health. By undertaking a simple blood test, we can find biomarkers that not only indicate disease, but also the development of future disease. The most important assets of serological tests are the measurement of proteins, cells, and antibodies. 

Serological diagnostic tests have broad applications in detecting and monitoring a variety of diseases. For example, they are pivotal in identifying infectious diseases, such as COVID-19, where serology tests detect antibodies against the virus and can indicate duration of immunity. More recently, attention has turned to using serology to identify disease in the absence of symptoms, especially slow forming and chronic diseases such as neurodegeneration and cancer that lack efficient screening methods. 

Serological profiling is a powerful technique for identifying these complex diseases. In this article, we focus on the techniques and applications of serology for disease detection. Additionally, its potential and future in medicine will be explored. 

Key Techniques in Serological Testing

Protein Analysis Using Enzyme-Linked Immunosorbent Assay (ELISA)

In serology, ELISA is a technique used for detecting and quantifying specific antibodies or antigens from a serum sample. It relies on an enzyme-linked antigen or antibody to produce a measurable signal that is usually accompanied by a color change, indicating the presence of the target substance. 

ELISA’s high sensitivity and specificity make it a go-to method for diagnosing various conditions. Examples include viral infections, such as HIV and hepatitis, and autoimmune diseases. It can also be used to analyze inflammatory cytokines from the immune system. However, ELISA is not without limitations. It has the potential for cross-reactivity, where the assay may detect antibodies other than those specific to the target antigen. This could lead to false-positive results. This technique also requires rigorously standardized protocols and reagents to ensure accuracy and reproducibility across different laboratories.

Protein Analysis Using Western Blotting

Western blotting serves as a confirmatory test to validate the presence of specific proteins or antibodies detected by ELISA. 

Serum proteins separated by gel electrophoresis are transferred to a membrane and probed with antibodies specific to the target antigen. Western blotting is renowned for its precision in identifying specific proteins with high sensitivity. Its identification capabilities makes it invaluable for diagnosing conditions like Lyme disease and certain types of cancers. As with ELISA, however, western blotting has limitations.

It involves a highly complex workflow that requires meticulous protocol adherence and significant technical expertise. This can lead to variability in results. Western blotting also has limitations in quantifying protein abundance, offering semi-quantitative results that are influenced by the linearity of detection for both the antibody and the detection method used.

Cell Analysis Using Flow Cytometry

Flow cytometry is a powerful technique that analyzes the physical and chemical characteristics of cell types or particles found in serum. Using modern microfluidics and laser optics, cells and proteins are pushed through a beam of light. Flow cytometry can simultaneously measure multiple parameters of single cells, including the expression of different surface molecules, allowing for the detection of specific cell populations and their immune status. 

There are many uses for flow cytometry. It is essential for: 

• Diagnosing blood cancers
• Identifying immune deficiencies
• Monitoring organ transplant rejection

Some limitations of Flow Cytometry include rigorous sample preparation procedures, complex datasets that require expertise to analyze, and potential phenotypic loss due to sample preparation procedures.

Antibody Analysis Using Protein Arrays

Notably, antibodies can also be measured using techniques like protein arrays. Antibodies are created by the immune system to combat a specific threat. Therefore, they can be used during testing to identify, monitor, and treat diseases. 

Antibodies are produced by B cells in response to encounters with unique or out of place proteins called antigens. In addition to common pathogens like bacteria or viruses, diseases like cancer and Alzheimer’s disease can also stimulate production of antibodies. 

A primary benefit of measuring antibodies in the blood is that antibodies access nearly all body compartments and remain in circulation throughout the disease process.

Antibodies are induced early in disease, often before symptoms, and can also persist in the blood long after the threat has subsided. As a result, they serve as early markers of disease as well as markers of disease progression and treatment effectiveness.  

Ultimately, antibody profiles are like fingerprints, with each antibody binding to a specific antigen. By analyzing the types and quantities of antibodies present in blood samples or other body fluids, serological analyses offer valuable insights into your health. 

Serology tests can provide information on: 

• Infectious diseases: Detecting specific antibodies can confirm if you have been exposed to or are currently fighting an infection.
• Autoimmune disorders: If your immune system mistakenly attacks your own healthy cells, serology can identify the specific antibodies involved. This aids in diagnosing conditions like rheumatoid arthritis.
• Cancer: Certain antibodies can target specific cancer cells or inflammatory molecules associated with cancer growth. They provide clues for early diagnosis and the monitoring of various cancers, like non small cell lung cancer.
• Neurodegeneration: Antibodies to protein tangles and other aberrant proteins found in neurodegenerative diseases can help identify diseases before symptoms preside , like amyotrophic lateral sclerosis (ALS) and Alzheimer’s.

Protein arrays can provide a large amount of data that may require bioinformatics expertise to analyze.

The Future of Serology

Serological diagnostic tests have broad applications in detecting and monitoring a variety of diseases. They are pivotal in identifying infectious diseases, such as COVID-19, where serology tests detect antibodies against the virus and can indicate duration of immunity. More recently, attention has turned to using serology to identify disease in the absence of symptoms, especially slow forming and chronic diseases such as neurodegeneration and cancer that lack efficient screening methods. 

Ongoing advancements in technology and methodology enable researchers to capture and understand the information held by the wide range of antibodies present in serum.  The development of high-throughput serological assays, such as functional protein microarrays, enables screening of autoantibodies across large sample sizes. The integration of high throughput approaches coupled with bioinformatics deciphers the enormous volume of data, ultimately leading to more precise and directed approaches to identifying, understanding and treating disease.