Immunology

Humoral effector mechanisms: compare antigen’s use of Fab regions and Fc regions

a) via Fab region: bind specifically to target antigens

b) via Fc regions: recruit secondary immune effectors (e.g macrophages/neutrophils to drive phagocytosis, NK cells to trigger perforin/granzyme release, C1 to initiate classical cascade and assemble MAC)

SCID and HIV are examples of which of the three paradigms the development of immunological principles relies on?

Accidents of Nature:

a) SCID: genetic failure of lymphocyte development

b) HIV/AIDS: pathological infection revealing central orchestrating role of CD4+ T Helper cells through their selective depletion

Dr. Edward Jenner is associated with which example of “Leap of faith paradigm”?

Small-pox vaccination: observed that milkmaids exposed to cowpox were protected from smallpox; inoculating individuals with cowpox material successfully induced protective cross-immunity

Who discovered antibiotic penicillin and what immunological paradigm is this associated with?

Alexander Fleming observed that contaminating mould (Penicillin) inhibited bacterial growth revealing antibiotic nature

Primary Lymphoid organs

1. Bone Marrow: Stem cells, B-cell production & maturation (T-cell origin only)

2. Thymus: T-cell maturationSe

Secondary Lymphoid organs

1. Spleen: filters blood, clears RBCs

2. Lymph nodes: filter lymph

3. Nodules: MALT, tonsils, Peyer’s patches

Where do immune precursors undergo antigen-independent development

Primary (central) lymphoid organs

Bi-lobed organ located superior to the heart

Thymus

Which lymphoid organ contains dendritic cells and macrophages while being the site of self-tolerance selection.

Thymus

Wich lymphoid organ atrophies post-puberty

Thymus

Lymph nodes are abundant in which wbc?

Macrophages and Dendritic cells

Which cells originate from the lymphoid lineage?

1. B-cells

2. T-cells

3. NK cells

Macrophages and Dendritic cells belong to which WBC lineage?

Myeloid lineage

Granulocytes (neutrophils, eosinophils, and basophils) belong to which wbc lineage?

Myeloid

Which secondary lymphoid organ filters systemic blood circulation, removing blood-borne pathogens and clearing aged or damaged erythrocytes

Spleen

What are Lymphoid Nodules / Mucosal-Associated Lymphoid Tissues (MALT)?

1. Their structural characteristic (how they differ from organs like lymph nodes or the spleen)

2. Their primary anatomical location

3. Three major anatomical examples

• Structural Characteristic: unencapsulated, dense aggregations of lymphocytes (unlike encapsulated secondary lymphoid organs such as lymph nodes and the spleen).

• Anatomical Location: environmental interfaces (mucosal boundaries) to continuously monitor, filter, and protect mucosal surfaces exposed to external antigens.

• Three Key Examples:

  1. Tonsils (oral/pharyngeal cavity)

  2. Peyer's Patches (small intestine)

  3. Appendix (junction of the small and large intestine)

ISF, pathogens or antigen-laden dendritic cells drain via afferent lymphatic vessels into organ?

regional secondary lymph nodes

Primary function of Macrophages residing in lymph nodes

Phagocytosis of microbes that enter lymph fluid

Primary function of Macrophages residing in lymph nodes

Dendritic cells in lymph nodes primarily activate naïve T cells by presenting antigen–MHC complexes.

What dual filtering role does the spleen perform in the circulatory and immune system?

The spleen removes pathogens from blood and destroys old erythrocytes

How does routing tissue fluid through secondary lymphoid organs prevent systemic sepsis?

Routing lymph through secondary lymphoid organs filters and traps local tissue pathogens via resident phagocytes before fluid reaches bloodstream

Primary function of eosinophils

Eosinophils are specialized in destroying multicellular parasites and participating in allergic reactions

What is the major distinction between Cytotoxic T cells (Tc) and NK cells?

Like Cytotoxic T cells, NK cells release perforin and granzymes to induce target cell apoptosis, however Cytotoxic T cells require specific antigen recognition through their TCR. NK cells do not require specific antigen recognition. Instead, they detect abnormal patterns, such as reduced MHC I expression or cellular stress; NK cells belong to innate (non-specific) immunity.

Three major phagocytic cell types and their primary location.

1. Fixed Tissue Macrophages: permanent residents of tissues that monitor for pathogens and tissue damage

2. Neutrophils: circulate in blood; rapidly recruited to sites of infection/injury

3. Monocytes: immature in blood; enter tissue to differentiate into Macrophages and Dendritic cells

which chemical mediators are released by basophils in the bloodstream

Basophils release inflammatory chemical mediators including histamine and prostaglandins.

What is CTLA-4, and what role does it play in T-cell activation?

CTLA-4 is an inhibitory receptor expressed on T cells. When it binds B7 on APCs, displacing CD28, it delivers an inhibitory signal that suppresses T-cell activation.

What are two major functions of fixed-tissue macrophages?

They phagocytose pathogens/debris and present antigens to T cells via MHC II.

Which immune cell is most associated with pus formation, and why?

Neutrophils; they are rapidly recruited to sites of infection and accumulate with dead cells and debris.

Why does an identical twin provide the lowest risk of kidney transplant rejection?

Because it is extremely unlikely that unrelated individuals express identical MHC Class I and II profiles; identical twins have essentially identical HLA/MHC molecules, so the immune system is unlikely to recognize the kidney as foreign.

A person develops immunity after recovering from a viral infection. What type of immunity is this, and why?

Natural active immunity; natural infection stimulates the person’s own immune system to produce antibodies and memory cells.

What antibodies are naturally present in type O blood, and why?

Anti-A and anti-B antibodies are present because type O RBCs lack both A and B antigens.

What antigens are found on AB-type RBCs?

Both A and B antigens are present; anti-A and anti-B antibodies are absent because because those antibodies would attack their own RBCs.

True or false; you normally make antibodies against the ABO antigens you do NOT have

What is main antibody isotype in mucosal secretions (e.g breast milk)

IgA (dimer; tetravalent)

Which immunoglobulin isotype (antibody class) is most abundant in serum?

IgG (monomer;divalent)

What antibody (Ig) region determines antibody isotype/class?

Fc region (constant domain of heavy chain)

What distinguishes an antigen from an antibody?

An antigen is the immune target; an antibody is the B-cell protein that specifically binds to it

What triggers cellular innate immune responses?

Recognition of PAMPS by Pattern Recognition Receptors (PRRs) including Toll-like receptors (primary family of integral transmembrane PRRs)

What are endogenous antigens? Provide an example

Endogenous antigens are proteins synthesized inside a host cell. When a virus infects a cell, it produced viral proteins intracellularly. These viral fragments are displayed on surface MHC Class I molecules to be recognized by Cytotoxic T cells (CD8+)

What is the role of Toll-like receptor’s extracellular domain and intracellular domain?

Extracellular domain: PAMP ligand binding

Intracellular signaling domain: activates downstream pathways to initiate secretion of pro-inflammatory cytokines, mounting innate immune response