IMMUNOLOGY EXAM 1 STUDY GUIDE

Flashcards covering primary and secondary lymphoid organs, immune cell development, inflammation, immunoglobulin classes, and diagnostic laboratory assays including syphilis and Lyme disease testing.

What are the primary lymphoid organs and their functions?

The primary lymphoid organs are the Bone Marrow (main source of hematopoietic stem cells, site for NK & B cell development) and the Thymus (site for T cell development).

What are the functions of the Spleen's red and white pulp?

The red pulp removes and destroys old RBCs, while the white pulp is lymphoid tissue containing PALS (T cells) and primary follicles (unstimulated B cells).

Where are Interdigitating DCs and Follicular DCs located within lymph nodes?

Follicular DCs reside in the cortex’s primary follicles; Interdigitating DCs reside in the paracortex.

List the seven steps of phagocytosis in order.

1. Physical contact (chemotaxis; opsonization), 2. Cytoplasm surrounds bacteria, 3. Phagosome forms, 4. Lysosomal granules fuse, 5. Phagolysosome forms and releases contents, 6. Bacteria digested by enzymes, 7. Release of debris via exocytosis.

What are the four major signs and symptoms of inflammation?

Redness, swelling, heat, and pain.

Describe the difference between acute and chronic inflammation regarding cell types.

Acute inflammation is characterized by neutrophils drawn to the site by chemotaxis; chronic inflammation involves lymphocytes infiltrating the area, leading to tissue damage and loss of function.

What is the relative immunogenicity of synthetic polymers, proteins, and lipids?

Proteins and polysaccharides are the best immunogens; synthetic polymers (e.g., nylon) are nonimmunogenic; nucleic acids and lipids are not immunogenic unless attached to a carrier.

Define 'Hapten'.

A small molecule that reacts with products of the immune response but is not capable of stimulating an immune response unless attached to a carrier.

What is the difference between an Alloantigen and a Heteroantigen?

Alloantigens are from other members of the same species (e.g., blood fusions), whereas Heteroantigens are from other species (e.g., plants, animals).

At what stage does a B cell express surface IgM and leave the bone marrow?

The Immature B cell stage.

What markers identify Treg cells and what is their function?

Treg cells express CD4 and CD25; they suppress the immune response to self-antigens.

Which CD markers are expressed by NK cells, and what is their function?

NK cells do not express CD4 or CD8; they are large granular lymphocytes that provide the 1st line of defense against virus-infected and tumor cells by mediating cytolytic reactions without prior exposure.

What do TLR2 and TLR4 specifically recognize?

TLR2 recognizes teichoic acid and peptidoglycan (Gram-positive bacteria); TLR4 recognizes lipopolysaccharide (Gram-negative bacteria).

Which antibody class is the most abundant in serum and can cross the placenta?

IgG, with a serum concentration of $800-1600\,mg/dL$. It crosses the placenta (except IgG2) to provide immunity for the newborn.

Which antibody is the most effective activator of the classical complement pathway and is diagnostic for acute infection?

IgM.

What is the role of the Secretory Component (SC) in IgA?

It attaches to Fc portions, facilitates transport to mucosal surfaces, and provides resistance to digestion by proteolytic enzymes.

Which antibody is the least abundant and triggers degranulation of mast cells and basophils?

IgE, with a serum concentration of $0.005\,mg/dL$.

Define 'Isotype', 'Allotype', and 'Idiotype'.

Isotype: Constant region of the H chain unique to each Ig class. Allotype: Minor sequence variations in the constant region of H or L chains. Idiotype: Unique variable portions of each chain serving as the antigen-binding region.

Compare the cleavage results of Papain vs. Pepsin on an Immunoglobulin.

Papain cleaves Ig into 3 fragments (2 Fab and 1 Fc); Pepsin cleaves Ig into 2 fragments (1 Fab and 1 Fc).

Define 'Affinity' and 'Avidity'.

Affinity is the initial force of attraction between a single Fab site and a single epitope; Avidity is the sum of all attractive forces, measuring the overall stability of the Ag-Ab complex.

What occurs during the 'Prozone' and 'Postzone' in precipitation reactions?

Prozone is antibody excess (unbound antibodies, no cross-linking); Postzone is antigen excess (every epitope bound to a single antibody, no cross-linking).

How does a competitive immunoassay differ from a noncompetitive immunoassay regarding the label signal?

In competitive assays, the amount of label is inversely proportional to the patient antigen concentration; in noncompetitive assays, the amount of label is directly proportional to the patient antigen concentration.

What is the principle of a Homogeneous Enzyme Immunoassay (EMIT)?

Labeled enzyme is inactivated when bound to an antibody; if patient antigen binds the antibody instead, the enzyme remains active, making enzyme activity (color change) directly proportional to the patient antigen concentration.

Describe the symptoms and typical timing of primary syphilis.

The primary stage features a painless, solitary chancre with raised, well-defined borders developing $10-90$ days after infection (average $21$ days) and lasting $1-6$ weeks.

What components make up the antigen used in nontreponemal syphilis tests?

A combination of cholesterol, lecithin, and cardiolipin.

Which test uses charcoal particles bound to cardiolipin-containing antigen?

RPR (Rapid Plasma Reagin).

In the FTA-ABS test, what is the purpose of absorbing patient serum with the Reiter strain?

To remove antibodies against nonpathogenic treponemes.

What are the Western Blot criteria for a positive Lyme disease diagnosis?

Positive for IgM if 2 of 3 specific bands (p23, p39, p41) are present; positive for IgG if 5 of 10 assessed bands are present.

What is the causative agent of Lyme disease and how is it transmitted?

Borrelia burgdorferi, transmitted by the Ixodes tick.

What is the principle of the ASO titer?

It detects antibodies to the streptolysin O enzyme. If ASO is present, it neutralizes the enzyme’s ability to lyse RBCs; therefore, a positive result is indicated by NO HEMOLYSIS.