Foundations II - Immunology Overview and Innate Immunity

Vocabulary flashcards covering essential terms and concepts from Foundations II: Immunology, focusing on innate immunity, barriers, cells, mediators, inflammation, and early host responses to viruses.

Immune system

System of cells, tissues, and soluble molecules that recognize and remove harmful entities and protect against pathogens, while surveilling for cancer and damaged cells.

Innate immunity

Non-specific, rapid first line of defense; constitutive barriers and inducible components; lacks immunological memory.

Adaptive immunity

Specific immune response with immunological memory, comprising humoral (B cells) and cell-mediated (T cells) components.

PAMP

Pathogen-associated molecular pattern; conserved microbial structures recognized by pattern recognition receptors (PRRs).

DAMP

Damage-associated molecular pattern; molecules released by stressed or dying cells that trigger inflammation.

PRR

Pattern recognition receptor; receptors that detect PAMPs and DAMPs to activate innate immune responses.

TLR

Toll-like receptor; a family of PRRs on cell surfaces or endosomes that detect microbial components and trigger signaling.

NLR

Nod-like receptor; cytosolic PRR that forms inflammasomes to activate inflammatory cytokines.

RLR

Rig-like receptor; cytosolic PRR recognizing viral RNA to trigger antiviral responses.

MALT

Mucosa-associated lymphoid tissue; lymphoid tissue at mucosal sites (including GALT, NALT, BALT, SALT).

SALT

Skin-associated lymphoid tissue; immune components in the skin.

GALT

Gut-associated lymphoid tissue; lymphoid tissue in the gut (e.g., Peyer’s patches) with secretory IgA involvement.

NALT

Nasopharynx-associated lymphoid tissue; includes tonsils and adenoids in the upper respiratory tract.

BALT

Bronchus-associated lymphoid tissue; lymphoid tissue in the bronchial airways.

M cell

Microfold cell; transports antigens across epithelium to underlying immune cells in gut-associated tissue.

Primary lymphoid tissue

Bone marrow and thymus; sites of lymphocyte production and maturation.

Secondary lymphoid tissue

Sites of initiation of immune responses (activation of lymphocytes); includes nodes, spleen, tonsils, Peyer’s patches, and MALT.

APC

Antigen-presenting cell; processes and presents antigens to T cells via MHC molecules.

Cytokine

Soluble mediator proteins that regulate immune responses; include interleukins, interferons, TNF, and growth factors.

Chemokine

A chemotactic cytokine that directs the migration of immune cells.

Antigen

Structure that elicits an immune response; can be a protein or polysaccharide.

Immunogen

Substance that elicits an immune response (distinct from a mere antigen in some contexts).

Antibody

Immunoglobulin produced by B cells that specifically binds an antigen; central to humoral immunity.

Antigen receptor

TCR or BCR; receptor complexes that recognize specific antigens; often require co-receptors for MHC interaction.

TCR

T cell receptor; recognizes antigen presented by MHC on APCs.

BCR

B cell receptor; membrane-bound antibody that recognizes specific antigens.

CD4

Co-receptor on helper T cells that stabilizes interaction with MHC II and supports T cell activation.

CD8

Co-receptor on cytotoxic T cells that stabilizes interaction with MHC I and supports killing of infected cells.

LFA-1

Leukocyte function-associated antigen-1; integrin on leukocytes that binds ICAM-1 to promote adhesion.

ICAM-1

Intercellular adhesion molecule-1; endothelial ligand for LFA-1 during leukocyte adhesion.

NK cell

Natural killer cell; innate lymphoid cell that kills virus-infected and tumor cells and secretes IFN-γ.

Neutrophil

Primary granulocytic WBC; first responders to infection; phagocytose microbes and release antimicrobial factors.

Macrophage

Phagocytic APC derived from monocytes; phagocytose pathogens, present antigen, and produce cytokines.

Dendritic cell

APC specialized in antigen presentation to T cells; bridges innate and adaptive immunity; types include plasmacytoid DCs producing Type I IFN.

Mast cell

Myeloid cell in tissues that releases histamine and other mediators during allergic reactions and inflammation.

Eosinophil

Granulocyte defending against parasites and involved in allergic responses; contains major basic protein and peroxidases.

Basophil

Granulocyte involved in allergic responses and parasite immunity; contains histamine and heparin.

Complement

Group of ~30 hepatic proteins activated via classical, MB-lectin, or alternative pathways; promotes lysis, opsonization, and inflammation.

Classical pathway

Complement activation triggered by antigen–antibody complexes.

MB-lectin pathway

Complement activation triggered by mannose-binding lectin binding to microbial surfaces.

Alternative pathway

Complement activation initiated by spontaneous C3 hydrolysis on microbial surfaces.

MAC

Membrane attack complex; C5b–C9 forms pores causing lysis of targeted microbes.

Opsonization

Coating of pathogens by C3b or antibodies to enhance phagocytosis.

Acute inflammation

Rapid, coordinated response delivering immune cells and mediators to tissue to eradicate pathogens and repair damage.

IL-1

Proinflammatory cytokine promoting fever and acute-phase responses.

IL-6

Proinflammatory cytokine driving fever and acute-phase protein production.

TNF-α

Proinflammatory cytokine involved in fever, inflammation, and vascular activation.

IL-10

Anti-inflammatory cytokine that dampens immune responses.

TGF-β

Anti-inflammatory cytokine that promotes regulation and tissue remodeling.

Type I interferons

IFN-α/β; antiviral state induction, upregulation of MHC I, and NK cell activation.

IFN-γ

Interferon gamma; activates macrophages and supports Th1 responses; enhances antigen presentation.

Perforin

Pore-forming protein used by NK cells and cytotoxic T cells to lyse target cells.

Granzyme

Serine proteases delivered by cytotoxic cells to induce target cell apoptosis.

ADCC

Antibody-dependent cellular cytotoxicity; NK cells kill Ab-coated targets via Fc receptors.

NETs

Neutrophil extracellular traps; extracellular DNA webs that trap and kill pathogens.

sIgA

Secretory IgA; IgA isotype in mucosal secretions, preventing pathogen adherence.

Peyer’s patches

Lymphoid aggregates in the ileum part of GALT; sites of antigen sampling and M-cell activity.

Lymph node

Secondary lymphoid organ where APCs present antigen to lymphocytes; contains subcapsular sinus and cortex.

MHC-I

Major histocompatibility complex class I; presents endogenous peptides to CD8+ T cells on all nucleated cells.

MHC-II

Major histocompatibility complex class II; presents exogenous peptides to CD4+ T cells on APCs.

M-cells (transcytosis)

Specialized epithelial cells in Peyer’s patches that transport antigens to underlying immune cells.

TLR4

TLR that detects LPS from Gram-negative bacteria; activates NF-κB signaling.

Inflammasome

Cytosolic multiprotein complex (often NLR-based) that activates caspase-1 and processes IL-1β and IL-18.

CXCL-8 (IL-8)

Chemokine that recruits neutrophils to sites of infection.

PAMP examples

LPS, peptidoglycan, lipoteichoic acid, flagellin, nucleic acids—molecular patterns recognized by PRRs.

DAMP examples

Uric acid crystals, heat shock proteins, ATP, DNA—endogenous danger signals triggering inflammation.