Chapter 16: Non-specific Defenses of the Host (Innate Immunity)

Vocabulary-style flashcards covering key concepts, terms, and mechanisms from the chapter on non-specific (innate) immunity and the body’s first and second lines of defense.

Innate immunity

Non-specific defenses present at birth that do not distinguish between pathogen types; activated by host cell receptors and cytokine release.

Toll-like receptors (TLR)

Host cell receptors that recognize pathogen-associated patterns and trigger innate immune responses, including cytokine release.

Cytokines

Proteins involved in cell-to-cell communication during immune responses.

Macrophages

Phagocytic leukocytes that engulf pathogens (phagocytosis) and can release signals like IL-1 and TNF-α to promote inflammation.

Dendritic cells

Antigen-presenting cells that link innate and adaptive immunity.

First line of defense

Physical and chemical barriers preventing pathogen entry (e.g., skin, mucous membranes, flushing actions).

Intact skin

Skin barrier with protective keratin and a natural dryness that deters microbial growth.

Keratin

Protective protein in the epidermis that contributes to skin barrier function.

Dryness factor

Normal dry skin environment that inhibits many microbes.

Mucous membranes

Line respiratory and other tracts; trap pathogens with mucus produced by goblet cells.

Goblet cells

Cells that secrete mucus to trap particles in mucous membranes.

Cilia

Hairlike structures that beat to move mucus and trapped debris out of the airways.

Mucus

Sticky substance that traps particulates (acts as flypaper) in the respiratory tract.

Flushing actions

Physical removal of pathogens via tears, saliva, urine, perspiration, vomiting, and diarrhea.

Low pH of stomach

Stomach pH around 2–4 denatures microbial proteins and reduces infection risk.

Skin pH

Acidic skin environment (pH 3–5) that inhibits many microbes.

Sebum

Oil from sebaceous glands containing fatty acids that inhibit some bacteria.

Lysozyme

Digestive enzyme in tears and perspiration that helps break down bacterial cell walls.

Amylase

Enzyme in saliva that participates in breakdown of carbohydrates; part of defense in oral cavity.

Second line of defense

Blood plasma and lymph components (leukocytes, phagocytosis, inflammation, fever, complement, interferon).

Leukocytes

White blood cells; major players in the second line, including granulocytes and agranulocytes.

Phagocytosis

Process where leukocytes engulf and digest foreign particles.

Phagosome

Vesicle containing a engulfed pathogen inside a phagocyte.

Phagolysosome

Fusion product of phagosome and lysosome where digestion occurs.

Lysosome

Organelle with digestive enzymes that fuse with phagosomes during digestion.

Defensins

Antimicrobial peptides that disrupt pathogen membranes.

Paracrins

Paracrine signaling molecules released to alert immune cells and promote inflammation (e.g., IL-1, TNF-α).

Inflammation

Redness, heat, pain, and swelling at a site; involves vasodilation, phagocyte migration (margination and emigration), and tissue repair.

Fever

Elevated body temperature that can enhance repair and inhibit pathogen growth.

Complement

A cascade of ~30 liver-produced proteins that aid innate and adaptive immunity, often by targeting extracellular antigens.

Interferon

Cytokine-like proteins especially active against intracellular pathogens (viruses).

Antigen

Substance foreign to the body recognized by the immune system.

Capsule

Glycocalyx capsule on bacteria that can hinder recognition by phagocytes and reduce lysozyme effectiveness.