HTH SCI 3103: Innate Immune Roundup

Comprehensive vocabulary flashcards reviewing the innate immune roundup lecture, covering tissue-resident cells, barriers, viral and bacterial recognition pathways, complement activation, NK cell cytotoxicity, and immune modules.

Tissue-resident cells

Cells stationed continuously within tissues (such as macrophages, mast cells, and dendritic cells) that carry out homeostatic maintenance, repair, and surveillance regardless of whether an infection is present.

Epithelial tight junctions

Mechanical barrier structures that join adjacent epithelial cells across mucosal and cutaneous surfaces to block pathogen entry into deeper tissues.

RIG-I

An intracellular pattern recognition receptor (PRR) that detects viral nucleic acids inside the cytoplasm of host cells.

Interferons

Cytokines released by virally infected cells that signal neighboring tissue cells to decrease protein synthesis and stimulate nearby immune cells to adopt anti-viral states.

Damage-Associated Molecular Patterns (DAMPs)

Endogenous molecules released by host cells upon injury or viral-induced lysis that are recognized by PRRs to activate innate immune cells.

Endosomal Toll-Like Receptors (TLRs)

Innate pattern recognition receptors located within the endosomal membranes of phagocytes that detect viral nucleic acids exposed inside phagolysosomes.

M1-like polarization

A pro-inflammatory phenotype adopted by macrophages upon TLR and interferon stimulation, characterized by upregulated killing machinery and secretion of pro-inflammatory cytokines.

Alternative Pathway

A complement activation pathway that initiates spontaneously upon contact with pathogen or viral surfaces in host tissues.

Lectin Pathway

A complement activation pathway triggered when circulating mannose-binding lectin (MBL) binds to specific glycoproteins on viral or microbial surfaces.

Opsonization

The deposition of complement fragments onto a pathogen surface, facilitating recognition and uptake by phagocytic cells via complement receptors.

Membrane Attack Complex (MAC)

A multimolecular pore formed by terminal complement proteins that inserts into membranes to directly lyse viral particles or target cells.

Chemokines

Chemotactic cytokines secreted by activated macrophages and other tissue cells that establish concentration gradients guiding circulating leukocytes to the site of infection.

Extravasation

The migration of circulating leukocytes (such as monocytes, NK cells, and neutrophils) out of the bloodstream and through vascular endothelium into infected tissue.

ILC1

Group 1 Innate Lymphoid Cells that belong to the Type 1 / cytotoxic immune module and produce cytokines to amplify defenses against intracellular viral infections.

MHC Class I inhibition

The constitutive mechanism by which normal cell-surface MHC class I molecules provide an inhibitory signal to Natural Killer (NK) cells to prevent the killing of healthy host cells.

Stress ligands

Molecules upregulated on virally infected or stressed host cells that engage activating receptors on NK cells to tip the balance toward target cell lysis.

NK Cell Cytotoxic Mechanisms

The pathways employed by Natural Killer cells to induce apoptosis in target cells, consisting of granzyme/perforin-mediated killing, death receptor ligation ($\text{FasL/Fas}$), and cytokine release ($\text{TNF-}\beta$ / $\text{TNF-}\\alpha$).

Efferocytosis

The phagocytic process through which tissue macrophages engulf and clear apoptotic cells, dead host cells, and cellular debris.

Micropinocytosis

The constitutive, non-specific uptake of extracellular fluids and solutes by dendritic cells to continuously sample their microenvironment for antigens.

Costimulatory molecules

Surface molecules upregulated on dendritic cells upon pathogen recognition via TLRs that are necessary alongside antigen presentation to activate naive adaptive immune cells.

Draining lymph node

The secondary lymphoid organ connected to the tissue via lymphatic vessels where antigen-bearing dendritic cells travel to prime naive T and B lymphocytes.

ILC3

Group 3 Innate Lymphoid Cells activated during extracellular bacterial infections to release cytokines and coordinate antibacterial immune defenses.

NETosis

A specialized neutrophil death program that extrudes web-like structures composed of chromatin and antimicrobial granule proteins to physically trap and kill extracellular bacteria.

ILC2

Group 2 Innate Lymphoid Cells activated during parasitic worm/helminth infections to orchestrate the type 2 immune response.

Degranulation

The rapid exocytosis of cytotoxic proteins and inflammatory mediators from intracellular granules by activated effector cells such as mast cells, eosinophils, and basophils.