L2:Innate Immunity: Leukocytes, Inflammation, Fever, and Complement Activation

Comprehensive vocabulary flashcards covering leukocytes, inflammation mechanisms, fever regulation, and complement cascade pathways based on lecture notes.

Granulocytes

White blood cells characterized by visible colored speckles or granules (vesicles functioning as storage compartments) in their cytoplasm when stained with eosin and methylene blue.

Eosinophils

Granulocytes whose vesicles absorb eosin to appear red; they fight multicellular parasites (such as hookworms or pinworms) by degranulating peroxides and digestive enzymes directly onto them.

Basophils

Granulocytes whose vesicles absorb methylene blue; they are packed with histamine to trigger inflammation and heparin to prevent clotting.

Heparin

An anticoagulant released by basophils that prevents blood clots from forming inside damaged blood vessels, maintaining blood flow to keep damaged tissue alive.

Neutrophils

The most abundant white blood cells; eukaryotic phagocytes with purple vesicles that absorb both eosin and methylene blue.

Phagosome

An internal membrane bubble containing an engulfed foreign particle, created when a phagocyte's plasma membrane ruffles, folds around the target, and pinches off.

Lysosome

A low-pH digestive organelle filled with peroxides and enzymes that is dragged along microtubules to fuse with a phagosome and destroy ingested particles.

Agranulocytes

White blood cells lacking stained granules because their vesicles do not absorb eosin or methylene blue; includes lymphocytes, monocytes, macrophages, and dendritic cells.

Lymphocytes

Agranulocytic white blood cells responsible for specific adaptive immunity.

Macrophages

Agranulocytic phagocytes capable of leaving the bloodstream and migrating into surrounding tissues to engulf foreign threats.

Monocytes

Immature macrophages circulating within the bloodstream.

Dendritic cells

A type of phagocyte characterized by surface spikes resembling neuronal dendrites, primarily involved in adaptive immunity.

Natural Killer (NK) Cells

Innate immune lymphocytes that respond to interferon by releasing perforin and granzyme to trigger apoptosis in infected host cells.

Interferon

A cytokine distress signal secreted by virally infected cells to warn neighboring cells to synthesize antiviral proteins and to recruit natural killer cells.

RNases

Antiviral enzymes produced by cells in response to interferon that degrade viral RNA or cellular RNA required for viral transcription and translation.

Perforin

A protein secreted by natural killer cells that inserts into the plasma membrane of a target cell, forming a pore that permits granzyme entry.

Granzyme

A protein released by natural killer cells that enters through perforin pores to initiate apoptosis inside the target cell.

Apoptosis

An orderly, controlled program of self-destruction in which a cell breaks into membrane-bound compartments that are safely consumed by phagocytes without releasing viral particles.

Edema

Swelling that occurs when inflamed capillaries become leaky and lose fluid faster than the lymphatic system can reclaim it, waterlogging the tissue.

Hypothalamus

The master endocrine gland located at the base of the brain that monitors the bloodstream for inflammatory signals and secretes prostaglandins to induce fever.

Prostaglandins

Cytokines released by the hypothalamus in response to circulating inflammatory signals that command the body to raise its internal thermostat.

Lipopolysaccharide (LPS)

An endotoxin lipid found in the outer leaflet of the outer membrane of Gram-negative bacteria whose toxicity is decreased by fever.

Complement System

A defensive cascade of over 30 inactive serum proteins circulating in the liquid portion of the blood that activate sequentially to combat infections.

C3a

A cleavage fragment of complement protein C3 that triggers mast cells to degranulate histamine, initiating inflammation.

C3b

A cleavage fragment of complement protein C3 that performs opsonization by adhering to bacterial surfaces, and also activates complement protein C5.

Opsonization

The process of coating a pathogen or foreign structure with molecules (such as C3b) to mark it for recognition and ingestion by phagocytes.

C5a

A cleavage product of complement protein C5 that activates mast cells and promotes positive chemotaxis by attracting macrophages toward the site.

Membrane Attack Complex (MAC)

A large, donut-shaped multiprotein structure made of one copy each of C6, C7, and C8, plus a ring of 12 to 16 copies of C9 that inserts into plasma membranes to cause cytolysis.

Cytolysis

Cellular destruction caused by the insertion of the membrane attack complex, allowing cellular contents to leak out and extracellular fluid to rush in.

Classical Pathway

The complement activation pathway initiated when an antibody binds a specific foreign target and activates complement protein C1, which then cleaves C2 and C4.

Heterodimer (C2a-C4b complex)

A two-part protein complex formed by the binding of complement fragments C2a and C4b that activates multiple copies of complement protein C3.

Alternative Pathway (Properdin Pathway)

The complement activation pathway in which Factor P (properdin), Factor B, and Factor D directly recognize and bind bacterial structures to activate C3.

Factor P (Properdin)

The primary complement protein of the alternative pathway that, alongside Factor B and Factor D, recognizes bacterial structures to activate complement protein C3.

Mannose-Binding Lectin

A liver-synthesized protein that binds mannose on bacteria or mannan on fungal cell walls, subsequently activating complement proteins C2 and C4.

Mast Cells

Histamine-containing cells of distinct cellular origin from basophils that release histamine when triggered by complement fragments C3a or C5a to drive inflammation.