Innate Immunity – Nonspecific Defense of the Host (Chapter 16, Part 1)

Vocabulary flashcards covering key terms and definitions from the lecture on innate immunity and the first line of defense.

Innate Immunity

Inborn, nonspecific defenses that include the first and second lines of defense against pathogens.

Adaptive Immunity

Acquired, specific immune response characterized by specificity, memory, and constituting the third line of defense.

First Line of Defense

Innate physical, chemical, and microbiota-based barriers that prevent pathogen entry.

Second Line of Defense

Innate internal defenses such as phagocytosis, inflammation, fever, antimicrobial substances, and NK cells.

Third Line of Defense

Adaptive immune responses—humoral and cell-mediated immunity—that target specific pathogens.

Physical Barriers

Structural features (skin, mucous membranes, ciliary escalator, etc.) that block pathogen entry.

Chemical Factors

Antimicrobial chemicals (sebum, lysozyme, gastric juice, etc.) associated with barriers that inhibit microbes.

Normal Microbiota

Resident microorganisms that protect the host by competitive exclusion and microbial antagonism.

Phagocytosis

Engulfment and digestion of microbes by cells like neutrophils and macrophages (second line defense).

Inflammation

Localized tissue response to injury or infection featuring redness, heat, swelling, and pain.

Fever

Systemic rise in body temperature that enhances immune function and inhibits pathogens.

Antimicrobial Substances

Broad category including complement, interferons, antimicrobial peptides, and iron-binding proteins.

Complement

Serum proteins that enhance phagocytosis, inflammation, and cell lysis.

Interferon

Cytokines that interfere with viral replication and modulate immune responses.

Antimicrobial Peptides

Short peptides that disrupt microbial membranes and are part of innate immunity.

Iron-Binding Proteins

Molecules (e.g., transferrin) that sequester iron to limit microbial growth.

Natural Killer (NK) Cells

Lymphocytes that kill virus-infected and tumor cells without prior sensitization.

Humoral Response

Adaptive immunity mediated by antibodies produced by B cells.

Cell-Mediated Response

Adaptive immunity involving T cells that destroy infected or abnormal cells.

Toll-Like Receptors (TLRs)

Host receptors that recognize PAMPs and trigger cytokine release to shape immune responses.

Pathogen-Associated Molecular Patterns (PAMPs)

Conserved microbial molecules recognized by TLRs (e.g., LPS, flagellin).

Cytokines

Small proteins released by cells that regulate intensity and duration of immune responses.

Skin

Primary physical barrier composed of dermis and keratinized epidermis that sheds and remains dry.

Dermis

Inner layer of skin made of connective tissue providing strength.

Epidermis

Outer layer of tightly packed epithelial cells containing keratin; forms a tough barrier.

Keratin

Protective, water-proofing protein in epidermal cells that resists microbial invasion.

Mucous Membranes

Epithelial linings of GI, respiratory, and genitourinary tracts that secrete mucus.

Mucus

Viscous glycoprotein that traps microbes and keeps mucous membranes from drying out.

Lacrimal Apparatus

Structures that produce and drain tears, mechanically washing the eye.

Ciliary Escalator

Ciliated mucosal mechanism that propels mucus-trapped microbes away from lungs.

Earwax

Cerumen that traps particles and inhibits microbe entry into the ear canal.

Urine Flow

Mechanical flushing action that cleanses the urethra of microbes.

Vaginal Secretions

Fluids that flush microbes out of the vaginal tract.

Peristalsis

Muscular contractions of GI tract that move contents and expel pathogens.

Sebum

Oily secretion forming a protective film on skin and lowering pH to 3–5.

Lysozyme

Enzyme in tears, saliva, perspiration, and urine that breaks down bacterial cell walls.

Gastric Juice

Stomach fluid with pH 1.2–3.0 that destroys most microbes and toxins.

Microbial Antagonism

Inhibition of pathogens by normal microbiota through competition and production of harmful substances.

Competitive Exclusion

Normal microbiota outcompeting pathogens for nutrients and space.

Probiotics

Live microbial cultures administered to confer a health benefit to the host.