Innate Immunity – Vocabulary Flashcards

A comprehensive set of vocabulary flashcards covering key terms, cells, molecules, and mechanisms involved in the innate immune response.

Innate Immunity

Natural, non-specific immune defense present from birth; responds within minutes and lacks immunologic memory.

Adaptive (Acquired) Immunity

Specific immune defense that develops after exposure to antigens and possesses immunologic memory.

Antigen

Any foreign molecule recognized as “non-self” by the immune system, triggering an immune response.

Humoral Immunity

Branch of immunity mediated by soluble molecules in body fluids, such as antibodies and complement.

Cell-Mediated Immunity

Immune protection carried out by cells, chiefly T lymphocytes and phagocytes, rather than soluble factors.

Physical Barriers

First-line defenses such as skin, mucous membranes, cilia, and the flushing action of tears, saliva, urine, and peristalsis.

Chemical Barriers

First-line antimicrobial factors including stomach HCl, lysozyme in tears, lactic and fatty acids in sweat, and vaginal acidity.

Normal Flora

Commensal microorganisms that compete with pathogens and secrete inhibitory substances like colicins or acids.

Pattern-Recognition Receptor (PRR)

Innate immune receptor that detects conserved microbial structures (PAMPs) or host damage signals (DAMPs).

Pathogen-Associated Molecular Pattern (PAMP)

Conserved microbial component (e.g., LPS, viral dsRNA) recognized by innate PRRs.

Damage-Associated Molecular Pattern (DAMP)

Endogenous molecule released by damaged or stressed cells, triggering innate immune responses.

Toll-Like Receptors (TLRs)

Family of membrane or endosomal PRRs (TLR1-TLR9) that detect diverse microbial molecules.

NOD-Like Receptors (NLRs)

Cytosolic PRRs (e.g., NOD1/2, NLRP inflammasomes) that sense bacterial peptidoglycan and cellular stress.

RIG-Like Receptors (RLRs)

Cytosolic sensors (RIG-I, MDA-5) that detect viral RNA and induce antiviral responses.

C-Type Lectin Receptors (CLRs)

Surface PRRs (e.g., Dectin-1, mannose receptor) that bind carbohydrate structures on microbes.

Natural Killer (NK) Cell

Large granular lymphocyte that kills virus-infected or tumor cells via perforin and granzymes; activated by IL-12 and secretes IFN-γ.

Perforin

Pore-forming protein released by NK cells that facilitates granzyme entry into target cells.

Granzyme

Serine protease delivered by NK cells to induce apoptosis in infected or malignant cells.

Phagocyte

Cell (e.g., neutrophil, macrophage, dendritic cell) that engulfs and destroys microbes through phagocytosis.

Phagocytosis

Process by which phagocytes ingest particles, form phagosomes, fuse with lysosomes, and kill microbes using ROS and enzymes.

Opsonin

Molecule such as antibody or complement protein that coats pathogens to enhance phagocytosis.

Opsonization

The coating of microbes with opsonins leading to more efficient binding and ingestion by phagocytes.

Reactive Oxygen Species (ROS)

Toxic oxygen metabolites generated by phagocyte oxidase that help kill engulfed microbes.

Inducible Nitric Oxide Synthase (iNOS)

Enzyme in activated phagocytes that produces nitric oxide, a microbicidal molecule.

Complement System

Cascade of plasma proteins that opsonize pathogens, recruit inflammatory cells, and can lyse microbes directly.

Acute-Phase Protein

Plasma protein (e.g., C-reactive protein, properdin) whose levels rise rapidly during inflammation and enhance host defense.

Interferon (Type I)

Cytokines IFN-α and IFN-β produced by virus-infected cells; induce antiviral state and up-regulate MHC I.

Inflammation

Localized protective response featuring vasodilation, increased vascular permeability, leukocyte recruitment, and mediators release.

Vasodilation

Expansion of blood vessels during inflammation, increasing blood flow, redness, and heat at the injury site.

Edema

Tissue swelling caused by leakage of plasma proteins and fluid during inflammatory response.

Chemotaxis

Directed movement of leukocytes toward chemical gradients (e.g., C5a, chemokines) at infection sites.

Neutrophil

Most abundant leukocyte; first responder phagocyte that releases antimicrobial granules and ROS.

Macrophage

Phagocyte derived from monocytes; engulfs pathogens, presents antigens, and produces cytokines such as TNF and IL-1.

Dendritic Cell

Antigen-presenting cell that captures microbes and migrates to lymph nodes to initiate adaptive immunity.

Mast Cell

Granulocyte in connective tissue that releases histamine and heparin, mediating allergic and inflammatory reactions.

Histamine

Vasoactive amine released by mast cells causing vasodilation and increased vascular permeability.

Tumor Necrosis Factor (TNF)

Pro-inflammatory cytokine from macrophages/T cells that activates endothelium, induces fever, and may cause cachexia.

Interleukin-1 (IL-1)

Cytokine that activates endothelium, induces fever, and promotes synthesis of acute-phase proteins.

Interleukin-6 (IL-6)

Cytokine stimulating acute-phase protein production in liver and promoting B-cell antibody responses.

Interleukin-12 (IL-12)

Cytokine that drives Th1 differentiation and activates NK cells to secrete IFN-γ.

Chemokine

Small cytokine that directs cell migration; examples include IL-8 and CCL2.

Fever (Pyrexia)

Elevated body temperature that accelerates immune functions and inhibits pathogen replication.

Peristalsis

Wave-like muscular contractions that propel contents along the gastrointestinal tract, expelling microbes.

Lysozyme

Enzyme in tears, saliva, and other secretions that hydrolyzes peptidoglycan in bacterial cell walls.

C-Reactive Protein (CRP)

Acute-phase protein that binds microbial phosphocholine, opsonizes pathogens, and activates complement.

Properdin

Complement component that stabilizes the alternative pathway C3 convertase, enhancing complement activation.

Beta-Lysin

Antibacterial protein released from platelets during coagulation.

Lactoperoxidase

Antimicrobial enzyme in saliva and milk that produces reactive iodine and hydrogen peroxide derivatives.