Innate Immunity II: Cellular Innate Immune Responses

Vocabulary flashcards covering key terms, receptors, cytokines, processes, and effector molecules of cellular innate immune responses.

Pattern Recognition Receptors (PRRs)

Receptors used by innate immune cells to detect conserved molecular signatures known as Pathogen-Associated Molecular Patterns (PAMPs).

Pathogen-Associated Molecular Patterns (PAMPs)

Conserved molecular signatures on pathogens detected by Pattern Recognition Receptors (PRRs).

Cytokine

A small protein released by cells that acts as a signaling molecule to regulate and coordinate immune responses, including inflammation, fever, cell recruitment, cell proliferation, and cell activation.

Phagosome

A membrane vesicle created when a pseudopod wraps around a pathogen and pinches it off inside a phagocyte.

Phagolysosome

A vesicle created by the fusion of a lysosome containing digestive enzymes with a phagosome, in which the pathogen is broken down.

Inflammation

The body's localized response to infection, injury, or harmful stimuli, characterized by redness, heat, swelling, pain, and loss of function at the site.

Fever

An elevated body temperature, typically defined as $>100.4^{\circ}\text{F}$ ($38^{\circ}\text{C}$), induced mostly by IL-1 and TNF-\alpha.

Leucine-rich repeats (LRRs)

The extracellular portion of a Toll-like Receptor (TLR).

TIR domain

The intracellular Toll/Interleukin-1 Receptor domain of a Toll-like Receptor (TLR).

TLR-4

A well-studied Toll-like Receptor that forms a complex with coreceptors MD2 and CD14 to recognize lipopolysaccharide (LPS) on Gram-negative bacteria.

IL-1\beta

A macrophage cytokine that increases vascular permeability and induces fever.

TNF-\alpha

A macrophage cytokine that increases vascular permeability and induces fever.

IL-6

A macrophage cytokine that induces the release of acute-phase proteins and induces fever.

CXCL8

A macrophage cytokine that recruits neutrophils to the site of infection.

IL-12

A macrophage cytokine that recruits and activates Natural Killer (NK) cells.

Rolling adhesion

The first stage of neutrophil migration where selectins on endothelial cells bind weakly to carbohydrate chains on neutrophil glycoproteins, allowing the neutrophil to roll along the vessel lining.

Tight binding

The second stage of neutrophil migration where CXCL8 recognition induces expression of integrins (e.g., LFA-1) that bind tightly to ICAM-1 on endothelial cells.

Diapedesis

The third stage of neutrophil migration where the neutrophil moves between endothelial cells by degrading extracellular matrix proteins with secreted proteases.

RIG-I

A widely expressed cytosolic innate receptor that binds intracellular PAMPs (e.g., viral RNA/DNA) and activates IRF3 to promote interferon expression.

Protein Kinase R

An interferon-induced enzyme in an infected cell that inhibits protein synthesis.

RNAse-L

An interferon-induced enzyme in an infected cell that destroys RNA in the cytosol.

p53

An interferon-induced protein in an infected cell that can induce apoptosis.

CD94:NKG2A

A common inhibitory Natural Killer (NK) cell receptor that binds MHC-I on healthy cells to prevent NK cell activation.

NKG2D

A common activating Natural Killer (NK) cell receptor that recognizes MIC stress ligands on infected cells.

2B4

A common activating Natural Killer (NK) cell receptor that recognizes CD48 stress ligands on infected cells.

Perforin

A cytotoxic protein released by activated Natural Killer (NK) cells that forms pores in the target cell membrane.

Granzymes

Cytotoxic molecules released by activated Natural Killer (NK) cells that enter through membrane pores and trigger apoptosis.