🔅 Serology is the scientific study of serum and other body fluids, especially for the detection of antibodies and antigens that are associated with certain diseases or conditions.

Serological tests are laboratory procedures that use serological reactions to diagnose or monitor various diseases, infections, immune responses, and blood types.

Serological tests have many applications in medicine, microbiology, immunology, transfusion medicine, and forensic science.

The history of serology dates back to the late 19th and early 20th centuries, when several scientists made important discoveries and contributions to the field. Some of the pioneers of serology include:

1). Jules Bordet; who discovered the complement system and its role in bacteriolysis and immune reactions.

2). Karl Landsteiner; who identified the ABO blood group system and the Rh factor, and developed the first serological test for syphilis.

3). August von Wassermann; who improved the serological test for syphilis and developed the complement-fixation test.

4). Paul Ehrlich; who coined the term "antibody" and proposed the concept of "side-chain theory" to explain antibody-antigen interactions.

5). Elvin Kabat; who discovered the structure and function of immunoglobulins and their role in antibody diversity.

Types of serological tests

– There are different types of serological tests, depending on the methods and principles used to detect antibodies and antigens. Some of the common types of serological tests are:

🔅 Agglutination tests

These measure the clumping of particles (such as red blood cells or bacteria) caused by antibodies binding to antigens on their surface.

Examples of agglutination tests include: blood typing, Widal test, and latex agglutination test.

🔅 Precipitation tests

These measure the formation of insoluble complexes of antibodies and antigens in a solution.

Examples of precipitation tests include: Ouchterlony test, radial immunodiffusion test, and immunoelectrophoresis.

🔅 Neutralization tests

These measure the ability of antibodies to inhibit or neutralize the biological activity of antigens (such as toxins or viruses).

Examples of neutralization tests include: toxin-antitoxin test, viral neutralization test, and antistreptolysin O test.

🔅 Complement-fixation tests

These measure the consumption of complement proteins by antibody-antigen complexes in a solution.

Examples of complement-fixation tests include: Wassermann test, Mazzini test, and C-reactive protein test.

🔅 Fluorescent antibody tests

These, use fluorescent dyes or markers to label antibodies or antigens and detect them by fluorescence microscopy or flow cytometry.

Examples of fluorescent antibody tests include: direct fluorescent antibody test, indirect fluorescent antibody test, and fluorescence in situ hybridization.

🔅 Enzyme-linked immunosorbent assays (ELISAs)

These tests, use enzymes to catalyze colorimetric or chemiluminescent reactions that indicate the presence or quantity of antibodies or antigens in a solution.

Examples of ELISAs include: sandwich ELISA, competitive ELISA, and indirect ELISA.

🔅 Western blotting

This test uses electrophoresis to separate proteins by size and transfer them to a membrane, where they are detected by specific antibodies labeled with enzymes or radioisotopes. Western blotting is often used to confirm the results of ELISAs or other screening tests.

Serological tests have many applications in diagnosis and monitoring of various diseases and conditions. Some of which are:

1). Serological tests can be used to diagnose infectious diseases caused by bacteria, viruses, fungi, parasites, or prions. Some examples of infectious diseases that can be diagnosed by serological tests include: syphilis, hepatitis, tuberculosis, Lyme disease, COVID-19, and Creutzfeldt-Jakob disease.

2). Serological tests can be used to determine the immune status or immunity of an individual to certain diseases or vaccines. Some examples of immunity tests include: measles IgG test, rubella IgG test, varicella-zoster virus IgG test, tetanus antitoxin test, and rabies antibody test.

3). Serological tests can be used to detect autoantibodies that are produced by the immune system against self-antigens in autoimmune diseases. Some examples of autoimmune diseases that can be diagnosed by serological tests include: rheumatoid arthritis, systemic lupus erythematosus, Sjögren's syndrome, celiac disease, and myasthenia gravis.

4). Serological tests can be used to determine the blood type and compatibility of donors and recipients in transfusion medicine. Some examples of blood group systems that can be tested by serological tests include: ABO.

5). Serological tests can be used to identify biological evidence and establish the identity or relationship of individuals in forensic science. Some examples of forensic serology tests include: blood typing, DNA profiling, paternity testing, and semen analysis.