Serology is the branch of immunology concerned with the study of serum and other body fluids to detect the presence of antibodies, antigens and other immune-related substances. It underpins many diagnostic tests used to determine past or current infection, immunity status and blood group compatibility.
Explanation
Serum is the clear fluid that remains after blood has clotted and cells and clotting factors have been removed. It contains antibodies produced by B lymphocytes and soluble antigens from pathogens. Serological tests exploit antigen‑antibody reactions to identify specific antibodies or antigens in a patient sample. Techniques include agglutination assays, enzyme-linked immunosorbent assays (ELISA), immunofluorescence, and western blotting. The detection of pathogen-specific antibodies can indicate previous exposure or ongoing infection; for example, serology is essential for diagnosing diseases such as syphilis, HIV infection and various viral hepatitis types. Measurement of antibody titers can help determine immunity after vaccination or natural infection, while detection of autoantibodies aids the diagnosis of autoimmune disorders. Serology also plays a central role in blood transfusion medicine through blood typing and crossmatching. Interpretation of serological results requires consideration of timing (early infection may yield false negatives), cross-reactivity and the difference between IgM and IgG responses. Despite limitations, serological testing remains a cornerstone of diagnostic and research laboratories due to its specificity and ease of use.
Applications and Examples
- Blood group determination and compatibility testing for transfusion or transplantation.
- Diagnosis of infectious diseases by detecting pathogen-specific antibodies or antigens (e.g., HIV, syphilis, COVID‑19, Lyme disease).
- Assessment of immune status after vaccination by measuring antibody titers.
- Detection of autoantibodies in conditions such as systemic lupus erythematosus, rheumatoid arthritis and autoimmune thyroiditis.
- Screening of donor blood and tissues for infectious agents to ensure safety of transfusions and transplants.
Through precise detection of antigen‑antibody interactions, serology provides invaluable information for clinical decision making, epidemiological surveillance and research.
Related Terms: Antibody, Antigen, Immunoassay, ELISA, Seroconversion