Anatomy & Physiology II - Lecture 24: Lymphatic System and Immunity

Comprehensive vocabulary flashcards covering the components of the innate and adaptive immune systems, cytokine signaling, the complement cascade, the inflammatory response, fever physiology, and antigen presentation from Anatomy & Physiology II Lecture 24.

Interleukin (IL)

A major category of cytokines produced by T-lymphocytes, macrophages, endothelial cells, and various other cells that primarily functions to regulate immune cells.

Tumor Necrosis Factor (TNF)

A category of cytokines secreted by T-lymphocytes, macrophages, mast cells, and dendritic cells that primarily destroys tumor cells, along with executing other immune functions.

Colony-Stimulating Factor (CSF)

Cytokines produced by T-lymphocytes and monocytes that stimulate leukopoiesis in bone marrow to increase the synthesis of a specific type (colony) of leukocytes.

Interferons (IFNs)

A group of antimicrobial cytokines produced by leukocytes, fibroblasts, and virus-infected cells; includes antiviral agents ($\text{IFN-}\alpha$ and $\text{IFN-}\beta$) and a pro-inflammatory agent ($\text{IFN-}\gamma$).

Innate Immunity

The nonspecific branch of the immune system that provides an immediate response to a wide array of foreign substances via external barriers, phagocytes, antimicrobial chemicals, and physiologic responses.

Adaptive Immunity

The specific branch of the immune system characterized by specificity and memory, producing a delayed response to specific antigens through T-lymphocytes and B-lymphocytes.

Lysozyme

An antibacterial enzyme found in sweat, saliva, mucus, and lacrimal fluid that attacks the cell walls of certain bacteria, particularly Gram-positive bacteria.

Defensins

Small antimicrobial proteins found in skin, sweat, and mucous secretions that form pores in the plasma membranes of microbes to compromise their structural integrity.

Dermicidin

A small antimicrobial protein secreted by the skin that functions as an antibacterial agent against Gram-positive and Gram-negative bacteria, as well as an antifungal agent.

Sebum

An oily secretion produced by sebaceous glands containing lactate and fatty acids that creates a low $\text{pH}$ ($3\text{--}5$) on the skin surface to inhibit microbial growth.

Hyaluronic Acid

A gel-like mucopolysaccharide located in the areolar tissue of the dermis and mucous membranes that slows the migration of microbes that breach epithelial boundaries.

Vibrissae

Coarse physical hairs located inside the nasal cavity that mechanically trap foreign microbes and airborne particles.

Cerumen

A waxy secretion produced within the external auditory meatus that waterproofs the ear canal and traps microbes.

Immune Surveillance

The continuous monitoring and patrolling of bodily tissues by natural killer (NK) cells to detect and destroy bacteria, transplanted cells, virus-infected host cells, and cancer cells.

Natural Killer (NK) Cells

Innate cytotoxic lymphocytes that induce apoptosis in abnormal, infected, or cancerous host cells by secreting pore-forming perforins and protein-degrading granzymes.

Perforin

A cytotoxic protein released by natural killer cells that polymerizes to form a transmembrane pore in the membrane of an unhealthy or unwanted target cell.

Granzymes

A group of protein-degrading enzymes secreted by natural killer cells that enter target cells through perforin pores to degrade cellular enzymes and induce apoptosis.

Eosinophils

Leukocytes of the innate immune system that specialize in destroying multicellular parasites by discharging cytotoxic chemicals directly onto them.

Basophils and Mast Cells

Pro-inflammatory chemical-secreting cells that release histamine, heparin, and eicosanoids to drive vasodilation, vascular permeability, and inflammation.

Complement System

A group of at least $30$ normally inactive plasma proteins produced by the liver (making up approximately $10\%$ of serum proteins) that activate in an enzymatic cascade to mediate opsonization, inflammation, cytolysis, and immune complex elimination.

Opsonization

The immune process of coating a pathogen with an opsonin, such as complement component $\text{C3b}$ or antibodies, to enhance binding and phagocytosis by leukocytes.

Membrane Attack Complex (MAC)

A multi-protein structure formed by complement proteins $\text{C5b}$, $\text{C6}$, $\text{C7}$, $\text{C8}$, and $\text{C9}$ that creates a channel in a microbial membrane, resulting in cytolysis via fluid influx.

Kinins

Active peptides (such as bradykinin) converted from plasma kininogen during injury that promote vasodilation, increase capillary permeability, elevate CAM production, and stimulate pain receptors.

Leukotrienes (SRS-A)

Eicosanoids synthesized from arachidonic acid in mast cells and basophils that mimic the effects of histamine but are released later and remain active longer.

Prostaglandins

Arachidonic acid-derived eicosanoids produced by mast cells and basophils that induce vasodilation, reset hypothalamic set points to generate fever, and sensitize pain receptors.

Margination

The inflammatory step in which circulating leukocytes slow down and adhere to cell-adhesion molecules (CAMs) displayed on the endothelial lining of blood vessels.

Diapedesis

The migration of recruited leukocytes as they squeeze between contracted endothelial cells of capillary walls into surrounding injured tissues.

Chemotaxis

The directed migration of immune cells along an increasing chemical gradient toward the source of inflammatory mediators and pathogens.

Exudate

Fluid, plasma proteins, and immune elements that leak into interstitial spaces at an injury site, washing the area before draining into lymphatic capillaries.

Pyrexia

An abnormal elevation of core body temperature (fever) triggered by trauma, infection, drugs, or tumors as an adaptive defense to accelerate repair and inhibit pathogen proliferation.

Exogenous Pyrogens

Fever-producing substances originating outside host cells, such as glycolipids located on bacterial and viral surfaces.

Endogenous Pyrogens

Host-derived fever-producing chemical messengers (including interleukins and interferons) released by active macrophages and neutrophils to stimulate the anterior hypothalamus.

Prostaglandin $E_2$ ($PGE_2$)

A local lipid mediator secreted by neurons in the anterior hypothalamus in response to pyrogens that raises the thermostat set point for body temperature.

Antipyretic

A drug or agent that reduces elevated body temperature by inhibiting the enzymatic synthesis of prostaglandin $E_2$ ($PGE_2$).

Stadium

The period of a fever during which core body temperature oscillates around the elevated hypothalamic set point while metabolic defenses are engaged.

Defervescence

The final stage of a fever marked by the return of the hypothalamic thermostat to its normal set point, causing body temperature to drop via heat dissipation.

Reye Syndrome

A serious condition in children under $15$ following acute viral infection that features brain neuron swelling, fatty visceral infiltration, and a $30\%$ mortality rate, typically triggered by aspirin use.

Cellular (Cell-Mediated) Immunity

The arm of adaptive immunity involving T-lymphocytes that directly attack and destroy foreign cells or diseased host cells harboring intracellular pathogens inaccessible to antibodies.

Humoral (Antibody-Mediated) Immunity

The arm of adaptive immunity mediated by B-lymphocytes and plasma cells that produce antibodies to neutralize pathogens present in extracellular body fluids.

Natural Active Immunity

Acquired resistance resulting from an individual's own direct production of antibodies or T-lymphocytes after natural exposure to a living pathogen.

Artificial Active Immunity

Acquired resistance produced by administering vaccines containing dead or attenuated pathogens to stimulate host antibody production and immunological memory.

Natural Passive Immunity

Temporary resistance achieved when a recipient acquires antibodies produced by another individual via maternal transfer through the placenta or breast milk.

Artificial Passive Immunity

Temporary protection conferred by the clinical injection of concentrated immune serum or antivenom harvested from an immunized human or animal donor.

Antigen

Any complex molecule with a molecular weight typically over $10{,}000\text{ amu}$ that can be recognized as foreign by the immune system and trigger an immune response.

Epitope

A specific structural domain or antigenic determinant on an antigen molecule that is recognized and bound by antigen receptors or antibodies.

Hapten

A small molecule that is non-immunogenic by itself but can stimulate an immune reaction after combining covalently with an endogenous host macromolecule.

Major Histocompatibility Complex (MHC)

A group of transmembrane self-antigen glycoproteins expressed on host cells that present antigenic peptides, enabling T-lymphocytes to differentiate self from foreign cells.

Antigen-Presenting Cells (APCs)

Specialized immune cells (including dendritic cells, macrophages, and B cells) that internalize exogenous antigens, digest them into peptides, and display them on surface MHC molecules.