Innate Immunity: Anatomical and Physical Barriers

Vocabulary flashcards covering key terms related to innate immunity and anatomical/physical barriers as presented in the notes.

Innate immunity

Natural or native immunity present from birth; non-specific, immediate defense that does not generate immunological memory.

Adaptive immunity

Specific immune response targeting particular antigens, involving lymphocytes and antibodies, with immunological memory.

First line of defense

Non-specific physical and chemical barriers (e.g., skin, mucous membranes) that prevent pathogen entry.

Second line of defense

Innate responses such as phagocytosis, complement, interferon, inflammation, and fever.

Physical barriers

Structural barriers (skin, mucous membranes) and their secretions that block pathogen entry.

Mechanical defenses

Physical processes that remove pathogens (e.g., skin shedding, ciliary movement, peristalsis, tearing).

Chemical factors

Chemical components like low pH, fatty acids, enzymes (lysozyme, pepsin), and antimicrobial peptides that inhibit microbes.

Microbiological barriers

Normal flora (commensal bacteria) that compete with pathogens and aid host defense.

Mucociliary clearance

Movement of mucus by cilia to remove particulates from the respiratory tract (mucociliary escalator).

Mucus

Sticky secretions coating epithelia to trap pathogens and facilitate removal.

Cilia

Hair-like projections that beat to move mucus and trapped particles out of the airways.

Lysozyme

Antimicrobial enzyme in tears, saliva, milk, and mucus that disrupts bacterial cell walls.

Defensins

Antimicrobial peptides that form pores in microbial membranes, causing cell lysis.

Lactoferrin

Iron-binding protein in milk and secretions that limits bacterial growth by sequestering iron.

Lactoperoxidase

Enzyme generating reactive oxygen species to damage microbes.

Paneth cells

Intestinal cells that secrete defensins, contributing to gut innate immunity.

HCl (gastric acid)

Acidic stomach secretion (pH ~2) that kills ingested microbes.

Bile and pancreatic detergents

Digestive secretions with detergent activity that disrupt microbes in the gut.

Normal flora

Residents of mucosal surfaces that competitively inhibit pathogen growth.

Commensal organisms

Nonpathogenic microbes that reside on body surfaces and aid defense; can influence immunity.

Opsonins

Molecules that coat pathogens to enhance phagocytosis.

Pattern recognition receptors (PRRs)

Innate receptors that detect conserved microbial motifs and trigger defense.

PAMPs (pathogen-associated molecular patterns)

Microbial motifs recognized by PRRs to activate innate immune responses.

Phagocytosis

Process by which phagocytes engulf and digest microbes and debris.

Complement system

Cascade of serum proteins that promotes lysis, opsonization, and inflammation.

Inflammation

Localized tissue response to injury or infection that recruits immune cells and mediators.

Fever

Systemic elevation of body temperature aiding pathogen control during infection.

Interferon

Cytokines that induce antiviral states and modulate immune responses.

NK cells

Natural killer cells; innate lymphocytes that destroy infected or abnormal cells.

Keratin

Structural protein in skin forming a waterproof, protective barrier.

Sebum

Skin oil creating an acidic, water-repellent surface that inhibits microbes.

Desquamation

Shedding of outer epithelial cells, helping remove adherent microbes.

Tears and lacrimal secretions

Eye secretions containing antimicrobial enzymes (e.g., lysozyme).

Mucosal secretions

Secretions (mucus, tears, saliva) that trap and flush pathogens.