Innate Immunity Practice Flashcards

A complete set of vocabulary flashcards covering the components, mechanisms, and recognition pathways of the innate immune system as described in the lecture notes.

Innate (Nonspecific) Immunity

The first and second lines of host defense, including physical barriers like skin, phagocytic cells, natural killer cells, inflammation, and fever.

Adaptive (Acquired) Immunity

The third line of defense involving specialized lymphocytes ($T$ cells and $B$ cells) and antibodies, characterized by a specific memory response.

PAMPs

Pathogen-associated molecular patterns; molecular structures characteristic of microbial pathogens, such as peptidoglycan or lipopolysaccharide, recognized by the innate immune system.

DAMPs

Damage-associated molecular patterns; endogenous molecules produced by or released from damaged and dying cells.

PRRs

Pattern Recognition Receptors; cellular or soluble receptors that recognize PAMPs and DAMPs.

Toll-like receptors (TLRs)

An evolutionarily conserved family of signaling PRRs expressed on leukocytes and other cell types that play essential roles in innate immune responses.

TLR4

A cell surface receptor that recognizes Gram-negative bacterial Lipopolysaccharide ($LPS$).

TLR5

A cell surface receptor that recognizes bacterial flagellin.

TLR3, 7, 8, and 9

Endosomal receptors that recognize microbial nucleic acids, such as $dsRNA$, $ssRNA$, and unmethylated $CpG$ DNA.

Neutrophils

The most abundant population of circulating white blood cells with a segmented nucleus of $3$ to $5$ lobules; they mediate the earliest phases of inflammatory responses.

Mast cells

Cells present in the skin and mucosal epithelium that express high-affinity receptors for $IgE$ and contain granules with vasoactive amines like histamine.

Küpffer cells

The specific name for tissue-resident macrophages located in the liver.

Alveolar dust cells

The specific name for tissue-resident macrophages located in the lung.

Dendritic cells

Antigen-presenting cells ($APC$) that capture antigens and present them to $T$ cells in the lymph nodes to bridge innate and adaptive immunity.

Opsonization

The process of coating a microbe with molecules like antibodies or complement proteins ($C3b$) to promote phagocytosis.

Phagolysosome

A cytoplasmic body formed by the fusion of a phagosome with a lysosome, where microbes are digested by enzymes.

Respiratory burst

A process in which phagocytes increase oxygen consumption to produce reactive oxygen species ($ROS$), such as superoxide anion ($O_2^-$) and hydrogen peroxide ($H_2O_2$), to kill microbes.

Chronic granulomatous disease (CGD)

A genetic defect in phagocyte oxidase components (most commonly $gp91$) that prevents the production of reactive oxygen species.

Natural Killer (NK) cells

Large granular lymphocytes that kill infected cells or cells lacking $MHC$ class $I$ molecules and secrete cytokines like IFN\text{-}\text{\textgamma}.

Perforin

A protein in $NK$ cell granules that forms pores in the target cell membrane.

Antibody-dependent cell-mediated cytotoxicity (ADCC)

A process where $NK$ cells bind to antibody-coated cells via $Fc$ receptors and destroy them.

Complement System

A group of serum proteins that interact in a cascade (Classical, Alternative, or Lectin pathways) to cause cell lysis, opsonization, and inflammation.

Membrane attack complex (MAC)

The terminal complex of the complement system ($C5b$, $C6$, $C7$, $C8$, and $C9$) that causes the lysis of certain pathogens.

C3a and C5a

Peptide mediators (anaphylatoxins) of inflammation and phagocyte recruitment produced during complement activation.

Acute phase proteins

Proteins produced by the liver in response to cytokines like $IL\text{-}6$, including $C\text{-}reactive$ protein and mannose-binding lectin.

Acute inflammation

The localized response of tissue to injury or infection, characterized by four symptoms: pain, swelling, redness, and heat.

Interferon-alpha (IFN\text{-}\text{\textalpha}) and Interferon-beta (IFN\text{-}\text{\textbeta})

Type $I$ interferons produced in response to viral infections that induce an antiviral state by blocking viral replication.

Costimulator

A second signal required for lymphocyte activation; for example, the membrane protein $B7$ on an $APC$ is required to activate naive $T$ cells.