Immunology Exam 1 study guide (Days 1-3)

List the WBCs and explain the role of each in the immune system

• Neutrophil—Most abundant WBC, performs phagocytosis

• Basophils—release histamine that maintain allergic reactions

• Lymphocytes—Target immune response; T, B, & NK cells

• Eosinophils—Release cytokines, phagocytosis, neutralizes products of allergic reactions

• Monocytes—cleanup crew, develop into macrophages

Differentiate between T cells, B cells, and NK cells, explaining their functions in the immune response

• T-cells: Mature in the thymus

  • T cells have 3 subsets that aid in killing infectious cells in the immune system and keep you healthy

• B-cells: Mature in the bone marrow

  • Major role in antibody production

• NK-cells: Mature in both the bone marrow and the 2nd lymphoid organs

  • kill virus infected cells

List the primary and secondary organs of the lymphoid system

• Primary: Bone Marrow, Thymus

• Secondary: Lymph nodes, Spleen, MALT, SALT

Differentiate between innate and adaptive immunity

Innate immunity:

• Prior exposure not required, memory not generated, immediate effects

Adaptive immunity:

• Memory is generated; the immune system remembers prior exposure.

List & explain the mechanisms of innate immunity

physical barriers, chemical shields, patrolling white blood cells, and blood proteins to prevent infection and alert the adaptive immune system

What are PRR’s, PAMPs, and TLRs and what is their role in the immune system

• PRRs: Pattern Recognition Receptors that are mainly found on surface of macrophages, sense cellular infection

• PAMPs: Molecules unique to infectious organisms, innate immune system quickly recognizes pathogens by using these

• TLRs: specialized sensor proteins of the innate immune system. They act as the body's alarm system, recognizing specific molecular signatures found on viruses, bacteria, and fungi to trigger a rapid inflammatory defense and activate the adaptive immune response

Steps of phagocytosis

engulf and destroy large particles, microorganisms, and cellular debris

Primary cells involved in phagocytosis

• Neutrophils

• Monocytes

• Macrophages

• Dendritic cells

What is an acute phase reactant, and how does it participate in the immune response

• Acute-phase reactants are serum proteins that increase or decrease rapidly in response to infection or injury

• Enhance contact between microbes and phagocytic cells

two key acute phase reactants

• C-reactive protein (CRP)

• Complement C3

How is adaptive immunity activated by the innate system

Antigen presentation

What steps are included in inflammation

recognition of the threat, recruitment of immune cells, removal of the harmful agent, regulation of the response, and tissue repair

List the 5 factors which affect the immune response

• Age

• Overall health

• Route of exposure to an antigen

• Antigen dose

• Genetic composition (MHC genes)

Antigen vs. Immunogen vs. Hapten

• Antigens are substances specifically recognized by the immune system

• Immunogens are substances capable of stimulating an adaptive immune response

• Haptens are small substances that are nonimmunogenic by themselves unless combined with a carrier

MHC Class I vs Class II Molecules

• MHC Class I molecules are expressed on ALL nucleated cells and process endogenous antigens

  • Highest on lymphocytes and myeloid cells

• MHC Class II molecules are found primarily on APCs and process exogenous antigens

What is the role of CD4 & CD8 T cells in immune response

• CD8 T cells bind to antigen class I MHC complex and destroy the target cell

• CD4 T cells stimulate B cells to divide and differentiate into antibody-producing plasma cells

Immunoglobulin structure

List & give characteristics for each of the different antibody classes

• IgG

  • predominant immunoglobulin in the serum, only immunoglobulin capable of crossing the placenta

• IgM

  • Largest Ig with its pentamer structure. It is the primary response antibody, first to appear during an immune response

• IgA

  • Major Ig in the body’s secretions, occurs as a dimer. present in breastmilk and transfers immunity to newborn infant

• IgD

  • Can serve as a receptor for antigen on the surface of B cells

• IgE

  • Binds to mast cells that mediates allergic reactions and defense against large parasites

Primary vs. Secondary antibody response

• Primary antibody response

  • 1st exposure to antigen: memory cells are generated; low-affinity antibody; longer lag phase

• Secondary antibody response

  • Memory response; shorter lag phase; high affinity antibody

Cell mediated immunity vs. Humoral immunity

• Cell mediated immunity

  • T Cells are the main component; cytotoxic T cells destroy cancer cells; helper T cells secrete cytokines

• Humoral immunity

  • B lymphocytes & antibodies; antibodies mark antigens for phagocytosis

What is the role of B cells in the immune response

• As plasma cells, they produce antibodies in BM & peripheral lymphoid organs

• B cells respond quickly to blood borne pathogens

What is the role of T cells (CD4 and CD8) in the immune response?

• T cells interact with APCs to initiate adaptive immune response

• T cells circulate throughout the bloodstream

What is the role of T regulatory cells?

• Suppress immune response to self-antigens and harmless antigens

• Secrete inhibitory cytokines that inhibit proliferation of other T-cell populations

Define affinity and avidity

• Affinity

  • Initial attraction force between a single Fab site on an antibody molecule and a single epitope on an antigen

• Avidity

  • Sum of attractive forces between an antigen and an antibody

Explain the Zone of Equivalence, Prozone, and Postzone in agglutination reactions.

• Zone of Equivalence

  • Number of multivalent sites of antigen and antibody is approximately equal

• Prozone

  • Antibody excess; no cross-linkages are formed; Antigen combines with only one or two antibody molecules

• Postzone

  • Antigen excess; No lattice network is formed; Small aggregates are surrounded by excess antigen

Explain the difference between Radial Immunodiffusion and Ouchterlony double diffusion.

Radial immunodiffusion is a single diffusion technique whereas Ouchterlony double diffusion is a double diffusion technique with three possible patterns as results

Explain Immunofixation electrophoresis

• Proteins in patient serum are electrophoresed, then antibody is applied directly to gel

• Precipitates form where antigen-antibody combination has taken place

Differentiate between Immunoturbidimetry and Nephelometry

Immunoturbidity involves decreasing light transmission as antigen concentration increases leading to turbidity. Nephelometry is light that is scattered at a measured angle, indicating the amount of an antigen or antibody present

Identify the following patterns

Explain the following agglutination methods:

a. Direct agglutination

b. Passive agglutination

c. Reverse passive agglutination

d. Agglutination inhibition

• Direct agglutination

  • Uses particles coated with naturally occurring antigens to test for antibodies in patient serum

• Passive agglutination

  • Uses particles coated with antigens not normally found on their surface; Antigen is attached to carrier particle, agglutination occurs if antibody is present

• Reverse passive agglutination

  • Antibody is attached to carrier protein, agglutination occurs if antigen is present in patient serum

• Agglutination inhibition

  • Competition between particulate antigens vs. soluble antigens in the patient sample for limited antibody-combining sites; Bacteria serves as the carrier of antibody

List the five general ways used to detect the causative agent of a bacterial infection

1) Culture of causative agent

2) Microscopic examination

3) Biochemical testing

4) Detection of bacterial antigens

5) Molecular detection of bacterial DNA or RNA

Pharyngitis symptoms and lab tests

• Symptoms

  • throat pain, difficulty swallowing, fever, and swollen lymph nodes

• Lab tests

  • Throat culture, Mononucleosis Test, RADT

impetigo symptoms and lab tests

• Symptoms

  • red sores that quickly burst, leaking fluid and forming distinctive amber or "honey-colored" crusts

• Lab tests

  • Blood or urine tests, biopsy, skin or nasal swab

Scarlet fever symptoms and lab tests

• Symptoms:

  • a distinctive sandpaper-like red rash, a high fever, and a swollen "strawberry" tongue

• Lab tests:

  • Throat cultures

  • Blood or antibody tests

Rheumatic fever symptoms and lab tests

• Symptoms

  • Fever, joint pain, inflammation of the heart

• Lab tests

  • ASO titer

  • Rapid strep test

Poststreptococcal glomerulonephritis symptoms and lab tests

• Symptoms

  • Malaise, abdominal discomfort, edema

• Lab tests

  • Urinalysis, serum complement levels

Explain the principle, interpretation, and clinical significance of the antistreptolysis O (ASO).

• Principle

  • Nephelometric methods are currently used that measure light scatter produced by immune complexes formed after binding of patient ASO to streptolysin-coated particles

• Interpretation

  • Generally (<200) IU/mL for adults and (<150 - 200) IU/mL for children, though this varies slightly by laboratory.

• Clinical significance

  • acute rheumatic fever (where \(>80\%\) of patients have elevated ASO) and post-streptococcal glomerulonephritis

Explain the principle, interpretation, and clinical significance of the streptozyme tests.

• Principle

  • The test uses sheep red blood cells (RBCs) coated with a cocktail of five key streptococcal exoantigens

• Interpretation

  • Positive Result: The presence of visible clumping or agglutination of the red blood cells indicates the presence of antibodies to one or more of the streptococcal antigens. Results can be reported qualitatively (positive/negative) or as a titer depending on the dilution. [1, 2, 3, 4]

  • Negative Result: A smooth, homogeneous suspension of cells without any clumping indicates the absence of these streptococcal antibodies (or levels below the limit of detection

• Clinical significance

  • The Streptozyme test is highly useful as a screening tool to identify past or recent Group A streptococcal infections, especially when evaluating patients for post-streptococcal complications

What disease state is associated with an elevated cold agglutinin titer and what is the minimum titer needed to be considered significance

CAD, minimum titer is ≥1:64

What are cryoglobulins and what disease are they associated with

• abnormal antibodies (immunoglobulins) in the blood that clump together, or precipitate, at cold temperatures and dissolve again when the body warms up

• Cryoglobulinemia

Name two Rickettsial infections and how they are transmitted

• RMSF

  • Transmitted by ticks

• Murine Typhus

  • Flea-borne disease

What testing methodology is used as the gold standard for Rickettsial diseases?

IFA

Name the two most common spirochete diseases?

• Syphilis

• Lyme Disease

List the clinical stages of syphilis and the symptoms present.

• Primary stage

  • Development of a chancre

• Secondary stage

  • Malaise, Fever, rash

• Latent stage

  • Asymptomatic

• Tertiary stage

  • Neurosyphilis

What syphilis testing is used for:

a. CSF =

b. Serum=

C. Confirmatory testing=

a.) Neurosyphilis

b.) Routine syphilis screening

c.) initial syphilis screenings

Distinguish treponemal from nontreponemal tests for Syphilis

• Nontreponemal

  • These tests do not look for antibodies against the syphilis bacterium itself. Instead, they detect "reagin" antibodies, which are produced by the body in response to cellular damage and lipids (such as cardiolipin) released during a syphilis infection

• Treponemal

  • These tests detect antibodies that specifically target the proteins of the syphilis bacterium

Explain the testing methodology associated with the VDRL and RPR

• VDRL

  • Patient serum is mixed on a slide with a cardiolipin-lecithin-cholesterol antigen suspension and clumping is used to identify the results

• RPR

  • Patient serum is mixed on a card with charcoal particles with cardiolipin antigen

Differentiate between the FTA-ABS and TP-PA treponemal tests

• FTA-ABS

  • A manual, indirect immunofluorescence assay. Patient serum is placed on a slide containing killed T. pallidum bacteria. If the patient has syphilis antibodies, they bind to the bacteria. A fluorescently tagged anti-human antibody is added, causing the spirochetes to glow under a fluorescence microscope

• TP-PA

  • An agglutination assay. Patient serum is mixed with gelatin particles coated with T. pallidum antigens. If antibodies are present, they cause the particles to clump (agglutinate) together and form a flat mat at the bottom of a microtiter well, whereas a negative result causes the particles to settle into a tight button

Which organism causes lyme disease?

B. burgdorferi, (black legged ticks)

What are the clinical manifestations of Lyme disease and what test method is most often used for identification?

• Stage 1

  • Localized rash

• Stage 2

  • Early dissemination

• Stage 3

  • Late dissemination with arthritis or neurologic symptoms

• Tests

  • EIA or IFA

Explain the differences between competitive and non-competitive binding in immunoassay.

• Competitive binding

  • All reactants are mixed together simultaneously; The amount of bound label is inversely proportional to the concentration of the labeled antigen

• Non-competitive binding

  • Patient antigen is captured by antibody bound to a solid phase; the amount of label is directly proportional to the amount of antigen in the patient sample

Differentiate between heterogeneous and homogeneous assay

• Heterogenous

  • Involves physical separation of bound and free components

• Homogenous

  • Do not require a physical separation step

Explain the following testing methodologies for immunoassay:

A. Enzyme immunoassay (EIA)

B. Radioimmunoassay (RIA)

C. Chemilluminescent immunoassay (CLIA)

D. Immunoflourescent assay (IFA

A. Highly sensitive assays that use enzymes as labels, which react with suitable substrates to produce breakdown products that may be chromogenic fluorescent, or luminescent

B. Measures trace amounts of analytes that are small in size. Is extremely sensitive and precise

C. Combines antigen-antibody immune reactions with chemiluminescent detection to quantify or qualify specific target molecules (like hormones, tumor markers, and infectious diseases) in patient samples

D. uses fluorescently labeled antibodies to detect specific antigens or antibodies in a sample

What is a capture or sandwich assay

a highly sensitive laboratory method used to detect and measure specific target proteins or antigens in a sample

What is a High-dose hook effect?

an analytical error in immunoassays (like an ELISA or pregnancy test) where extremely high concentrations of a target substance paradoxically produce a falsely low or negative result