chapter 18: practical applications of immunology

introduction: practical applications of immunology

• test “applications” = “uses”

  • use of substances (Ag) that trigger immune response (humoral/CMI)

    • ex. vaccines: inject Ag → make Ab → dz PREVENTION

  • testing/analysis of pt’s blood (serum) sample

    • ex. serological testing: look for Ag’s or Ab’s in blood (pt sample) → accurate + timely dx

history of immunity & vaccination

inoculation of Cowpox virus to prevent Smallpox (1st vaccine)

vaccine

injection of substances (antigens) into the body → induce immune response

• ex. make Ab’s (humoral immune response)

vaccination

(“vacca” = cow)

1. provokes a primary immune response → leads to formation of memory B cells and Ab’s (b/c just completed clonal selection & clonal expansion)

2. produces a rapid & intense secondary immune response

immunogen

a substance (Ag) that stimulates the immune system

herd immunity

protection for most of the population

desirable criteria for an ideal vaccine

1. vaccine safety: never pathogenic or toxigenic

2. vaccine effectiveness: strong immunogen & stimulate immune system

3. vaccine w/ oral administration: preferred over injectable vaccine

4. vaccine requires only one injection or combination preferred

5. vaccine is affordable & easy access

types of vaccines (live, inactivated, toxoid)

• live, attenuated (weakened) vaccines: weakened pathogens, closely mimic actual infection (mild SE)

  • ex. MMR vaccine

• inactivated, killed vaccines: killed pathogens, safer than live vaccines

  • ex. polio & influenza vaccines

• toxoid vaccines: inactivated toxin, immune response will target toxin (make Ab → antitoxin)

  • ex. Td vaccine

types of vaccines (conjugated, subunit, mRNA)

• conjugated vaccines: main vaccine component combined w/ strong immunogen (protein) → strong immune response

  • ex. pneumococcal vaccine (capsule + protein)

• subunit vaccines: use antigenic fragments to stimulate immune response

  • ex. hep B & pertussis vaccines (DTaP)

• mRNA (nucleic acid) vaccines: inject only bacterial/viral nucleic acid

  • inject mRNA into host cells → make protein Ag’s → stimulate (STRONG) host immune response

  • ex. COVID-19 vaccines

common vaccines and preventable diseases (summary)

serological testing

• serology: study or diagnostic examination of blood serum (see how immune system responds to pathogens or substances introduced into body)

  • tested: serum w/ no clotting factors (vs. plasma w/ clotting factors)

  • look for Ag (pathogen) or Ab (IgM)

  • purpose: accurate & timely diagnosis

• positive test: yes Ag or Ab → yes dz

• negative test: no Ag or Ab → no dz

desirable criteria for an ideal serological test

• high specificity/accuracy: unambiguous (1 interpretation → 100% +/-), reliable (no false +/-)

  • ex. pregnancy test, HIV test, athlete drug doping test

• high sensitivity: use small sample size; detect small quantities Ag’s or Ab’s

• easy set-up & interpretation: simple, easy to read

• high throughput: ability to simultaneously test hundreds or thousands of samples (many @ one time d/t machine automation)

• affordable cost & easy access: available to most & reasonable cost

serological tests: direct vs indirect testing methods

• direct serological test: look for Ag (pathogen)

  • lab test (Ab) + pt. sample (Ag)

• indirect serological test: look for Ab (IgM)

  • lab test (Ag) + pt. sample (Ab)

• some exist as both direct/indirect tests (4 outcomes)

  • patient serum sample → lab test → make diagnosis

common examples of serological tests

1. Precipitation Reactions & Agglutination Reactions

2. Neutralization Reactions

3. Fluorescent-Antibody Techniques

4. Compliment-Fixation Reactions

5. ELISA

precipitation reactions

• involve