BIO 151 Notes.docx

Epithelium

Layers of keratinized cells that line organs and inner cavities such as the respiratory tract, GI tract, and urogenital tract.

Mucosal surface

The inner lining of organs that secretes mucus and has beating cilia to remove mucus and unwanted material.

Sebaceous glands

Glands located in hair follicles that secrete sebum to inhibit bacterial growth.

Antimicrobial peptides

Peptides produced by all epithelia that perturb pathogen membranes.

Tears and saliva

Body fluids that contain lysozyme, an enzyme that degrades bacterial cell walls.

Acidic environments

Environments such as the stomach, vagina, and skin that have acidic pH levels.

Innate Immune System

The body's first line of defense that responds to infections before the adaptive immune system and can extinguish localized infections within a few days.

Recognition

The process in which soluble proteins and cell-surface receptors bind to pathogens or altered cells to mark them for elimination.

Recruitment

The process in which effector mechanisms provided by effector cells, such as complement proteins, recruit other cells to kill and eliminate pathogens.

Cytokines

Soluble secreted proteins that trigger and regulate the innate immune response.

Adaptive Immune System

The immune system that adds/enhances the innate immune response, has specificity and diversity in recognizing antigens, undergoes clonal selection and expansion, and generates immunological memory.

Clonal selection

The process in which lymphocytes are selected by antigens for activation to produce specific antibodies.

Clonal expansion

The proliferation of lymphocytes specific for an antigen after exposure, increasing the number of cells with identical receptors for the antigen.

Immunological memory

The ability of the adaptive immune system to generate long-lived memory cells specific for an antigen, leading to a stronger and faster immune response upon subsequent exposures to the antigen.

Hematopoiesis

The process of blood cell formation, where leukocytes are derived from pluripotent hematopoietic stem cells.

Erythroid Lineage

The lineage that gives rise to erythrocytes (red blood cells) and megakaryocytes (platelet precursors).

Myeloid Lineage

The lineage that gives rise to granulocytes, monocytes, and macrophages, which play important roles in innate immunity.

Dendritic cells

Cells that determine whether and when the innate immune response needs support from the adaptive immune response and carry intact and degraded pathogens to lymphoid organs to initiate the adaptive response.

Mast Cells

Cells resident in all connective tissues that play a role in inflammation and have violent spasms of smooth muscle to eject parasites from respiratory and GI tracts.

Lymphoid Lineage

The lineage that includes natural killer cells, B cells, and T cells, which play roles in adaptive immunity.

Humoral Immunity

Immunity mediated by antibodies that facilitate the engulfment and destruction of extracellular microbes by phagocytes.

Lymphoid Tissues

Tissues that include the bone marrow, thymus, spleen, adenoids, tonsils, appendix, lymph nodes, and Peyer's patches, where lymphocytes develop, mature, and become stimulated.

Antibody Responses

The immune response mediated by B lymphocytes (B cells) that produce plasma cells and antibodies.

Cell-mediated Immune Responses

The immune response mediated by T lymphocytes (T cells) that recognize antigens presented by major histocompatibility complex molecules and can kill infected cells.

Spleen

An organ that filters blood to remove damaged and senescent red blood cells and defends against blood-borne pathogens.

Mucosa-associated Lymphoid Tissue (MALT)

Secondary lymphoid tissue in mucosal tissues that defends against pathogens that enter through the mucosal epithelium.

Complement System

A system of plasma proteins that opsonize bacteria and extracellular virus particles, and can damage pathogen membranes.

Thioester bond

A bond that is exposed to the hydrophilic environment upon cleavage.

Alternative Pathway

A pathway that starts with the binding of C3 with water and leads to C3 activation, deposition of C3b, and recruitment of effector mechanisms.

C3 convertase

Proteases that cleave and activate C3.

Regulatory Proteins

Proteins such as factor P, factor H, and factor I that regulate complement activation by binding to C3b and preventing its degradation or further cleavage.

Macrophage

The first effector cell to encounter invaded tissue, prevalent in connective tissues and linings of GI and respiratory tracts, and enhances phagocytosis through surface receptors.

Complement Receptor 1 (CR1)

Binds to C3b fragments on the pathogen surface and facilitates engulfment of the pathogen into endosomes or phagosomes.

Terminal Components

C5, C6, C7, C8, and C9 proteins that cooperate to form the membrane-attack complex (MAC) and disrupt the integrity of the pathogen membrane.

Soluble Proteins

S protein, clusterin, and factor J that prevent the association of the C5b, C6, and C7 complex with cell membranes.

Inflammatory Peptides

C3a and C5a fragments that act as ligands for receptors on phagocytes, endothelial cells, and mast cells, increasing inflammation at the site of complement activation.

Plasma Proteins

Proteins involved in the coagulation system and kinin system, which are activated in response to vessel damage by pathogens and promote blood clot formation and vasodilation.

Protease inhibitors

Proteins that inhibit the activity of microbial proteases, preventing them from hiding from the immune system.

Defensins

Antimicrobial peptides that neutralize toxins and promote unfolding of microbial toxins, making them susceptible to proteases.

Lectins

Carbohydrate-specific receptors found in macrophages that recognize structural features on microbes and trigger phagocytosis and elimination.

Pattern-recognition receptors (PRRs)

Receptors that recognize pathogen-associated molecular patterns (PAMPs) and damage-associated molecular patterns (DAMPs) to identify pathogens and initiate immune responses.

Scavenger receptors

Receptors that trigger phagocytosis, cell adhesion, and intracellular signaling to identify and eliminate microbes and unwanted macromolecules.

Toll-like Receptors

Receptors that recognize specific pathogen-associated molecular patterns (PAMPs) and initiate immune responses.

Toll-like receptors (TLRs)

Signaling receptors present on immune cells that respond to a range of microbial and viral products.

TLR4

The main macrophage receptor for LPS (lipopolysaccharide) that recognizes the lipid A component of LPS.

LPS

Lipopolysaccharide, a component of the outer membrane of Gram-negative bacteria.

Leucine rich repeat region (LRR)

Repeated leucine residues in the pathogen-recognition domain of TLR4 that give each type of TLR a different ligand specificity.

TIR domain

Toll/interleukin-1 receptor domain, the cytoplasmic domain of TLR4 that signals the macrophage to transcribe genes encoding proteins needed for the innate immune response.

CD14

A protein at the macrophage surface that forms a complex with TLR4 and MD2 to recognize and deliver LPS.

MyD88

An adaptor protein that interacts with the TIR domain of TLR4 and engages IRAK4 to initiate TLR4 signaling.

IRAK4

Interleukin-1 receptor-associated kinase 4, a protein kinase that is phosphorylated by MyD88 and activates TRAF6.

TRAF6

Tumor necrosis factor receptor-associated factor 6, a protein that is phosphorylated by IRAK4 and leads to the activation of the IKK kinase complex.

IKK

Inhibitor of kappa-B kinase, a kinase complex that phosphorylates inhibitor of kappa-B (IkB) to release nuclear factor kappa-B (NFkB) and initiate the transcription of genes encoding cytokines and adhesion molecules.

NEMO Deficiency

NFkB Essential Modulator Deficiency, a condition caused by the loss of the y subunit (NEMO) of IKK, which impairs the activation of NFkB and macrophages by TLR4 signaling.

TLR Sensing

Receptors on the plasma membrane and within endosomal vesicles that recognize various ligands on pathogens and distinguish them from human DNA and RNA.

NOD Proteins

Intracellular receptors that recognize bacterial degradation products in the cytoplasm and initiate signaling pathways leading to the activation of NFkB and the production of inflammatory cytokines.

RIG-I-like receptors (RLRs)

Cytoplasmic proteins that detect viral nucleic acids and produce Type I Interferons to interfere with viral replication and alert the immune system.

Inflammasomes

Protein complexes formed by NLRs that detect infection and cleave pro-IL-1B into active IL-1B, which is then released by macrophages to initiate inflammation.

Pyroptosis

A form of programmed cell death characterized by cytokine release, pore formation, and the death of macrophages.

IL-1a

An interleukin involved in homeostasis that is constitutively expressed by healthy cells.

Autoinflammatory Diseases

Chronic and recurrent bouts of systemic inflammation mediated by cells of the innate immunity and not involving adaptive immunity.

Macrophage

Long-lived immune cells that reside in tissues and work from the start of infection to raise the alarm and improve the efficiency of pathogen capture and digestion.

Neutrophils

Short-lived immune cells that circulate in the blood and are recruited to infected tissues by macrophages to defend against pathogens.

IL-1B

Interleukin-1B, a master regulator of inflammation that is released by activated macrophages and has various effects on immune cells.

CXCL8

A chemokine released by macrophages to attract neutrophils to the site of infection.

Adhesion molecules

Proteins on the surface of leukocytes and tissue cells that mediate their interaction and facilitate the migration of neutrophils from the blood to infected tissues.

Diapedesis

The process by which neutrophils leave the blood by squeezing between cells.

Pyogenic bacteria

Bacteria that cause the formation of pus.

Neutrophil Granules

Intracellular compartments in neutrophils that contain antimicrobial components and are released upon activation to kill pathogens.

Respiratory burst

An increase in oxygen consumption by neutrophils that leads to the generation of reactive oxygen species to kill pathogens.

NADPH oxidase

An enzyme complex in neutrophil granules that facilitates the respiratory burst and raises the pH of the phagosome to kill pathogens.

Neutrophils

White blood cells that deliver granules and undergo apoptosis after delivering them.

Apoptosis

Programmed cell death that occurs in neutrophils after delivering granules.

NETosis

A process in which neutrophils release neutrophil extracellular traps (NETs) to capture and kill pathogens.

NETs

Neutrophil extracellular traps that are released by neutrophils to capture and kill pathogens.

Nucleus swell and burst

The swelling and bursting of the nucleus in neutrophils during the process of NETosis.

Chronic Granulomatous Disease (CGD)

A genetic syndrome caused by defective genes encoding NADPH oxidase subunits, resulting in the inability to produce functional NADPH oxidase and respiratory burst.

NADPH oxidase

An enzyme complex responsible for the respiratory burst in neutrophils.

Phagosome

A vesicle formed during phagocytosis that contains the engulfed pathogen.

Granulomas

Nodules formed by the concentration of infected macrophages that are unable to digest infected neutrophils.

Fever

An increase in body temperature caused by the release of cytokines IL-1B, IL-6, and TNF-a, which act on temperature-control sites in the hypothalamus and muscle and fat cells to generate heat.

Pyrogens

Cytokines IL-1B, IL-6, and TNF-a that act as fever-inducing agents.

Acute-Phase Response

The production of plasma proteins by the liver in response to IL-6, resulting in changes in the levels of acute-phase proteins.

Acute-phase proteins

Proteins that increase or decrease in concentration during the acute-phase response, such as C-reactive protein (CRP) and serum amyloid A.

C-reactive protein (CRP)

An acute-phase protein that targets phosphorylcholine of lipopolysaccharide (LPS), acts as an opsonin, and triggers the classical pathway of complement activation.

Serum Amyloid A

An acute-phase protein that interacts with Toll-like receptors (TLRs) and scavenger receptors (SRs) to activate cells to produce inflammatory cytokines.

Lectin Pathway

An innate immune response induced by infection and initiated by the acute-phase protein mannose-binding lectin (MBL) binding to the pathogen surface.

Mannose-binding lectin (MBL)

An acute-phase protein that binds to mannose-containing carbohydrates on the pathogen surface, acting as an opsonin and facilitating the uptake of the pathogen by monocytes.

Classical Pathway

A complement activation pathway that requires the binding of antibody or C-reactive protein to the pathogen surface, leading to the cleavage and activation of complement components and the formation of classical C3 convertase.

NK cells

Cytotoxic innate lymphoid cells that circulate in the blood and enter infected tissues to provide type I immunity.

Helper Innate Lymphoid cells (ILCs)

Innate lymphoid cells that function similarly to adaptive CD4 T cells and secrete cytokines to activate effector cells such as macrophages and granulocytes.

Innate Lymphocyte Precursor

A common lymphocyte precursor cell that gives rise to various types of innate lymphocytes, including NK cells, helper ILCs, LTi cells, and ILC1-3.

NKp

Precursor of NK cells derived from the common precursor of all innate lymphocytes.

CHILp

Precursor of all innate helper lymphocytes derived from the common precursor of all innate lymphocytes.

LTIp

Precursor of lymphoid-tissue inducer (LTi) cells derived from the common precursor of all innate lymphocytes.

ILCp

Common precursor of ILC1-3 derived from the common precursor of all innate lymphocytes.

NK Cytotoxicity

The ability of NK cells to kill infected cells by inducing apoptosis.

TLR3, TLR7, TLR8

Toll-like receptors expressed by NK cells that recognize viral RNA and activate signaling pathways leading to the production of interferons.

Dendritic Cells

Antigen-presenting cells that interact with NK cells and play a role in the initiation of adaptive immune responses.

Immunoglobulin

A general term for proteins produced by B cells that recognize antigens, with antibodies being the free-floating form.