Pathophysiology Chapter 2: Innate and Adaptive Immunity Flashcards

100 comprehensive vocabulary flashcards testing terminology, cell types, pathways, and clinical conditions across all sections of Chapter 2.

Host resistance

The capacity to prevent microorganisms from causing disease, categorized as non-specific (protecting against many agents) or specific (targeting particular agents).

Pathogenic Bacteria

Unicellular prokaryotes causing surface or deep-tissue infections that often secrete toxins causing further cellular damage.

Pathogenic Viruses

Acellular agents that enter human cells and replicate inside them.

Pathogenic Fungi

Unicellular (yeast) or multicellular organisms damaging skin, mucous membranes, or lungs, some of which produce lethal toxins.

Helminths

Multicellular eukaryotes that infest the intestines, disrupting nutrient absorption and causing cellular damage.

Pathogenic Protozoa

Unicellular eukaryotes (e.g., Plasmodium falciparum) transmitted by mosquito bite and responsible for malaria.

Mucociliary escalator

The mechanism by which cilia sweep mucus containing trapped pathogens toward the glottis for swallowing.

Mucin proteins

Sticky proteins contained in mucus produced by goblet cells that trap debris and microbes.

Sebum

Bactericidal oil secreted by sebaceous glands containing lysozymes, antibodies, and defensins.

Defensins

Antimicrobial peptides present in sebum that disrupt bacterial and fungal structure or metabolism.

Lactoferrin

An antimicrobial protein found in vaginal secretions and seminal fluid that sequesters iron, depriving bacteria of a required resource.

Bile

An alkaline fluid produced by the liver and stored in the gallbladder containing bile salts that act as potent antimicrobial agents.

Hematopoiesis

The process of blood cell formation, which begins in the yolk sac at day 7, moves to the liver and spleen at week 7, and transitions to the bone marrow at approximately week 20.

Hemocytoblasts

Pluripotent stem cells located in the bone marrow that give rise to all blood cell types.

Erythropoietin (EPO)

A hormone secreted by the kidneys in response to low blood-oxygen levels to stimulate red blood cell production.

Retic Count

The proportion of red blood cells that are reticulocytes, normally ranging from $1\text{--}2\times 10^{-2}$ ($1\text{--}2\times 10^{-2}$ or $1\text{--}2\text{\%}$).

Hematocrit

The percentage of total blood volume made up of RBCs, averaging approximately $42\text{\%}$ in adult females and $46\text{\%}$ in adult males.

Leukopenia

A reduction in white blood cell production resulting from bone marrow disorders, autoimmune diseases, severe infections, or medications.

Thrombocytopenia

A condition characterized by reduced platelet production, leading to prolonged bleeding and petechiae.

Neutropenia

A decreased neutrophil count caused by severe infection, nutritional deficiency, congenital defects, autoimmune disease, or cancer.

Neutrophilia

An elevated neutrophil count in the blood, commonly associated with bacterial infections.

Eosinophilia

An elevated eosinophil count caused by helminth infections, allergies, or autoimmune diseases.

Lymphocytosis

An elevated count of NK cells, T lymphocytes, and B lymphocytes, typically occurring with viral infections.

Polycythemia

An elevated RBC count, which thickens blood and increases clot risk, caused by blood doping, chronic hypoxia, or dehydration.

Granulocytes

White blood cells containing large, visible granules and irregularly-shaped nuclei, including neutrophils, eosinophils, mast cells, and basophils.

Diapedesis

The process by which white blood cells perform amoeboid movement to emigrate from blood vessels into surrounding tissues.

Neutrophils

The most abundant white blood cells ($50\text{--}70\text{\%}$) with a 2–5 lobed nucleus that act as first responders to phagocytose bacteria and release NETs.

Neutrophil Extracellular Traps (NETs)

Structures composed of chromatin fibers and proteases released by neutrophils to trap extracellular pathogens.

Eosinophils

Granulocytes comprising $2\text{--}3\text{\%}$ of WBCs that exocytose toxins to kill large parasites, contain RNases, and release VEGF.

Mast Cells

Tissue-resident immune cells located in skin dermis, lung mucosa, and GI tract containing granules with heparin and histamine.

Basophils

Circulating counterparts to mast cells containing granules filled with heparin and histamine that mediate pro-inflammatory responses.

Monocytes

Immature phagocytic leukocytes circulating in blood that mature within 1–3 days into fixed macrophages, free macrophages, or dendritic cells.

Microglia

Fixed macrophages specifically located in brain tissue.

Dust cells

Fixed macrophages situated within lung tissue.

Kupffer cells

Fixed macrophages residing in the liver.

Langerhans cells

Fixed macrophages located in the skin.

Dendritic Cells

Antigen-presenting cells residing in skin and mucosa that migrate to lymph nodes upon activation to stimulate T and B lymphocytes.

Natural Killer (NK) cells

Cytotoxic innate lymphocytes ($5\text{--}20\text{\%}$ of lymphocytes) that lyse target cells lacking self-antigens.

Perforin

A protein released by NK cells and CD8+ T cells that creates portals in target cell membranes.

Granzymes

Proteases released by NK cells and CD8+ T cells that enter target cells through perforin pores to induce apoptosis or cleave microbial proteins.

Chemotaxis

The directed migration of phagocytes and leukocytes following chemical gradients to sites of infection or tissue injury.

Opsonins

Molecules such as antibodies, lectin, and complement proteins that coat pathogens to facilitate phagocyte adherence and binding.

Phagosome

An internal cellular vesicle formed when a phagocyte extends pseudopods to encircle a pathogen.

Phagolysosome

A cytoplasmic vesicle formed by the fusion of a phagosome with a lysosome where lytic enzymes digest the pathogen.

Complement system

A collection of over 30 liver-produced blood proteins that participate in opsonization, MAC formation, and mast cell activation.

Membrane Attack Complex (MAC)

A pore structure assembled from complement proteins C5–C9 on bacterial cell walls, causing osmolytic swelling and cell rupture.

Classical pathway

A complement cascade initiated when C1 binds two antibodies complexed with surface antigens on a pathogen.

Lectin pathway

A complement pathway triggered when liver-produced Mannose-Binding Lectin (MBL) binds to mannose on microbial surfaces.

Alternate Pathway

An antibody-independent complement pathway initiated by Properdin, Factor B, and Factor D directly recognizing pathogens.

Alpha Interferons (Type I)

Signalling glycoproteins produced by virally-infected host cells that induce AVP production in neighbouring cells to block viral replication.

Beta Interferons (Type I)

Anti-inflammatory interferons produced by fibroblasts released in preparation for tissue healing after infection.

Gamma Interferons (Type II)

Interferons released by NK cells, CD8+ cytotoxic T cells, and CD4+ helper T cells that stimulate macrophage activity.

Chemokines

Cytokines that direct white blood cell migration and recruitment to infection or injury sites.

Lymphokines

Cytokines produced by T lymphocytes to attract macrophages and stimulate B lymphocytes.

Interleukins

Helper T cell-derived cytokines that activate macrophages, induce fever, promote lymphocyte differentiation, and stimulate hematopoiesis.

Bradykinin

A vasoactive peptide produced from kininogen cleavage that induces vasodilation, increases capillary permeability, and stimulates nociceptors.

Exudate

Protein- and cell-rich plasma fluid that leaks from capillaries into damaged tissue spaces during inflammation.

Hyperemia

Increased local blood flow to a tissue bed causing the characteristic redness associated with inflammation.

Serous exudate

Watery inflammatory fluid containing minor proteins and WBCs, commonly seen in unruptured burn blisters.

Fibrinous exudate

Thick, sticky inflammatory fluid containing fibrin, associated with severe injuries and increased scar tissue formation.

Purulent exudate

Thick, yellow-green fluid containing WBCs, dead microorganisms, and tissue debris (pus), characteristic of bacterial infections.

Hemorrhagic exudate

Inflammatory fluid containing red blood cells resulting from severe damage to local blood vessels.

Systemic Inflammatory Response Syndrome (SIRS)

A life-threatening condition caused by a cytokine storm leading to massive vasodilation, capillary leakage, hypotension, and circulatory shock.

Fever of unknown origin (FUO)

A systemic febrile response thought to result from inflammatory responses to undetected cellular damage, trauma, infection, or drug reactions.

Endogenous Pyrogens

Body-derived cytokines (such as interferons and interleukins) that stimulate the hypothalamus to elevate the body's temperature set point.

Exogenous Pyrogens

Foreign fever-inducing substances, such as lipopolysaccharides (LPS) from bacterial cell walls.

Prodromal stage

The initial onset phase of a fever where pyrogens begin circulating and an individual starts feeling unwell.

Chills stage

The fever phase during which the hypothalamic set point is raised, causing cold sensations, shivering, vasoconstriction, and goosebumps.

Flush stage

The period during a fever when core body temperature reaches or exceeds $37.2^\text{o}\text{C}$ and remains elevated.

Defervescence stage

The defervescence or sweating stage of fever where pyrogens decline, resetting the thermostat to $37^\text{o}\text{C}$ via sweating and vasodilation.

Primary lymphoid organs

Anatomical sites (bone marrow and thymus) responsible for immune cell production and maturation.

Secondary lymphoid organs

Lymphoid structures (lymph nodes, spleen, MALT) that serve as main sites for lymphocyte activation and antigen screening.

Cisterna chyli

A sac-like lymphatic vessel situated below the diaphragm that collects lymph from the gut and lower body before entering the thoracic duct.

Thoracic Duct

The main lymphatic trunk draining lymph from most of the body into the left subclavian vein.

Right Lymphatic Duct

The lymphatic duct responsible for draining lymph specifically from the right upper limb, right thorax, and right sides of the head and neck.

GALT

Gut-Associated Lymphoid Tissue (including Peyer's patches and the appendix) that monitors mucosal surfaces in the digestive system.

MALT

Mucosa-Associated Lymphoid Tissue consisting of immune cells distributed throughout mucosal linings of respiratory, GI, and urogenital tracts.

T Cell Receptor (TCR)

A specialized antigen-binding surface protein generated on T cells through somatic recombination in the thymic cortex.

Positive Selection (T cells)

A thymic cortex selection process where T cells displaying weak or moderate binding to self-MHC survive and express CD4 or CD8 co-receptors.

Negative Selection (T cells)

A thymic medulla process where T cells binding strongly to self-peptides undergo apoptosis to eliminate autoreactive cells.

Regulatory T (Treg) cells

T cells generated from moderate self-antigen binding during negative selection that actively suppress effector T cell proliferation.

Self-restriction

The functional requirement that mature T cells bind foreign antigens only when displayed on self-MHC molecules.

Self-tolerance

The state of immunological unresponsiveness preventing mature lymphocytes from reacting against the body's own antigens.

MHC Class I

Cell surface molecules present on nearly all nucleated host cells that present intracellular antigens to CD8+ cytotoxic T cells.

MHC Class II

Surface molecules expressed exclusively on APCs (macrophages, dendritic cells, B cells) that present processed extracellular antigens to CD4+ helper T cells.

Cell-mediated immunity

Adaptive immune defenses driven directly by activated CD8+ and CD4+ T cells targeting intracellular pathogens and abnormal host cells.

Humoral immunity

Adaptive immunity mediated by B cells and circulating antibodies targeting extracellular pathogens and soluble toxins.

APC Licensing

Feedback signaling from activated CD4+ helper T cells to APCs that upregulates CD80/CD86 ligands to enhance cytotoxic T cell activation.

Plasma cells

Effector B cells specialized in secreting large quantities of antigen-specific antibodies into circulation.

Agglutination

An antibody action where antibodies cross-link pathogens into large clusters, preventing contact with healthy cells.

Neutralization

An antibody mechanism where antibody binding directly blocks viral attachment sites or inactivates bacterial exotoxins.

Hemostasis

The rapid physiological process consisting of vascular spasm, platelet plug formation, and blood coagulation to prevent blood loss.

Vascular spasm

The initial phase of hemostasis where vasoconstrictors induce smooth muscle contraction to narrow the lumen of damaged blood vessels.

Coagulation

The third stage of hemostasis in which soluble plasma fibrinogen is converted into insoluble fibrin threads that fortify the platelet plug.

Fibrinolysis

The breakdown of a fibrin clot by active plasmin, which is activated from plasminogen by tissue-type plasminogen activator (tPA).

Albumin

The predominant plasma protein ($60\text{\%}$) produced by the liver, responsible for generating colloid osmotic pressure and transporting lipid-soluble molecules.

C-reactive protein (CRP)

An acute-phase liver protein that binds dead cells and microbes to activate complement, serving as a serum biomarker for inflammation.

Erythrocyte Sedimentation Rate (ESR)

A diagnostic blood test measuring the rate at which RBCs settle, which accelerates in the presence of elevated inflammatory plasma proteins.

Fibrosis (Replacement)

A tissue repair outcome in non-regenerative tissues where functional parenchyma is permanently replaced by scar tissue produced by fibroblasts.

Granulation tissue

Fragile, vascularized pink repair tissue formed during proliferation containing new capillaries, fibroblasts, and collagen.