Applications of Immunology

Vaccinations
- Used to immunize individuals against diseases.
Types of Vaccines:
- Live attenuated vaccines:
- Pathogen is weakened through chemical treatments or culturing in unsuitable environments.
- These vaccines multiply in the host body and provoke an immune response.
- Inactivated vaccines:
- Pathogens are killed by heat or chemicals.
- Vaccine components still promote an immune response.
- Toxoids:
- Inactivated toxins used to immunize against specific toxins (e.g., tetanus and diphtheria toxoids).
- Acellular vaccines:
- Use only fragments of the pathogen to promote an immune response, minimizing potential adverse reactions.
- Subunit vaccines:
- Produced by recombinant DNA technology (e.g., Hepatitis B, Recombivax®) by cloning viral proteins into yeast cells to use as vaccines.

CDC recommendations for childhood and adult vaccinations:
- Vaccination schedule varies by age from birth to ≥65 years old, with several recommended vaccines:
- Children: Hepatitis B, DTaP (diphtheria, tetanus, pertussis), MMR (measles, mumps, rubella), IPV (inactivated polio), etc.
- Adults: Boosters such as Tdap (tetanus, diphtheria, pertussis) and Td (tetanus and diphtheria) recommended every 10 years.
- There are catch-up immunization schedules for those who miss vaccinations.

Serological Testing:
- Serum from patients is tested for antibodies/antigens to determine exposure, ongoing infection, or vaccination against specific antigens.
Immunodiagnostics Techniques:
- Various tests rely on the binding of antibodies to antigens, including:
  - Agglutination
  - Hemagglutination
  - Precipitation
  - Fluorescent antibody methods
  - ELISA assays (Enzyme Linked Immunosorbent Assay)
  - Complement fixation tests

Patient antibodies bind to specific antigens in solution, leading to visible precipitation, indicating a positive reaction.
Primarily qualitative (yes/no) assessment.

Agglutination occurs when viruses agglutinate RBCs if antibodies against the virus are absent; it will not occur if antibodies are present.
Can also be quantitative to determine antibody titers through serial dilutions of patient serum.

Commercially available antibodies labeled with radioactive, fluorescent, or enzyme markers are utilized to identify specific antigens from patient samples.
UV microscopy is used for viewing the fluorescent antibodies.

A classic test for diagnosing diseases (e.g., syphilis).
Performed in vitro by adding patient serum to an antigen, and complement fixation is detected using sheep erythrocytes.

Utilizes plastic microtiter plates for detecting either antibodies (indirect ELISA) or antigens (direct ELISA).
Steps for Indirect ELISA:
1. Antigen is attached to the well in a plate.
2. Blocking protein (gelatin) is added to prevent uncoated surfaces from binding.
3. Patient serum is added, allowing antibodies to bind to the antigen.
4. Enzyme-linked anti-antibody is added to bind to the bound antibody.
5. A substrate for the enzyme is added, leading to a color change indicating a reaction.

Key for many diagnostic tests; made by fusing sensitized mouse B-cells with myeloma cells in vitro to form hybridomas, producing specific antibodies continuously in culture.

Technique used to identify antigens in patient samples (e.g., HIV testing).
Involves separating proteins via electrophoresis, transferring them to a nitrocellulose membrane, and probing with a specific solution to check for the presence of HIV antigens.

Uses dipstick techniques where antibodies are linked to colloidal metals; visible color change indicates the presence of specific antigens (e.g., Strep A test).

Test Types and Uses:
- Immunodiffusion, agglutination, viral neutralization, complement fixation, ELISA, and Western blot, each serving specific diagnostic purposes related to various infections and conditions.