Comprehensive Microbiology Review: Key Vocabulary from Chapters 11-21

A set of vocabulary flashcards covering the essential terms, cells, molecules, pathways, diseases, and clinical concepts highlighted across the microbiology lecture chapters on innate immunity, adaptive immunity, immune disorders, and representative infectious diseases.

Innate Immunity

Immediate, non-specific first line of host defense that lacks memory but rapidly contains pathogens and activates other immune responses.

Physical Barrier

Structural feature (e.g., skin, mucous membranes) that prevents pathogen entry into the body.

Chemical Barrier

Antimicrobial substance (e.g., low pH, lysozyme, defensins) that inhibits or destroys microbes at body surfaces.

Skin (as a barrier)

Keratinized, tightly packed epithelial layer with acidic, salty secretions and normal microbiota that blocks microbial invasion.

Mucous Membrane

Epithelial lining producing mucus; traps pathogens and employs cilia, lysozyme, and low pH for defense.

Normal Microbiota

Resident microbes that competitively exclude pathogens and contribute to host defense on skin and mucosa.

Phagocytosis

Cellular process in which phagocytes ingest, kill, and digest microbes through phagosome-lysosome fusion.

Neutrophil

Most abundant WBC; short-lived first responder that performs potent phagocytosis and releases antimicrobial NETs.

Macrophage

Long-lived phagocyte derived from monocytes that acts as an antigen-presenting cell and cytokine producer.

Dendritic Cell

Highly phagocytic APC in skin and mucosa that bridges innate and adaptive immunity by activating naïve T cells.

Natural Killer (NK) Cell

Lymphocyte that kills virus-infected or tumor cells lacking normal MHC I by inducing apoptosis.

Basophil

Granulocyte that releases histamine during allergic reactions and parasitic infections; similar mediators as mast cells.

Mast Cell

Tissue resident cell with histamine-rich granules that triggers inflammation and allergy upon IgE cross-linking.

Eosinophil

Granulocyte specialized for attacking helminths and participating in allergic responses via toxic granule proteins.

Complement System

Cascade of ~30 plasma proteins that opsonize pathogens, promote inflammation, and form membrane attack complexes.

Opsonization

Coating of microbes (e.g., with C3b or antibodies) to enhance recognition and phagocytosis.

Membrane Attack Complex (MAC)

Complement components C5b-C9 that polymerize to form lethal pores in pathogen membranes.

Classical Pathway

Antibody-dependent complement activation route that links adaptive and innate immunity.

Lectin Pathway

Complement activation initiated by mannose-binding lectin binding microbial carbohydrates.

Alternative Pathway

Antibody-independent complement activation triggered by spontaneous C3 hydrolysis on microbial surfaces.

Cytokine

Small secreted protein that mediates communication and regulation among immune cells.

Chemokine

Cytokine subgroup that directs cell chemotaxis toward infection or injury sites.

Interleukin (IL)

Cytokine family primarily facilitating communication between white blood cells.

Interferon (IFN)

Cytokine type with potent antiviral effects and ability to activate immune cells.

Tumor Necrosis Factor (TNF)

Pro-inflammatory cytokine that can induce fever, apoptosis, and septic shock when overproduced.

Acute-Phase Protein

Liver-derived plasma protein (e.g., CRP, MBL) whose levels rise rapidly during inflammation and infection.

Lactoferrin

Iron-binding protein that limits microbial growth by sequestering free iron.

Defensin

Cationic antimicrobial peptide that disrupts bacterial, fungal, and viral membranes.

Inflammation

Localized tissue response to damage or infection characterized by redness, heat, swelling, pain, and loss of function.

Cardinal Signs

Classic clinical indicators of inflammation: rubor, calor, tumor, dolor, functio laesa.

Diapedesis

Process by which leukocytes squeeze through endothelial gaps to reach infected tissue.

Pattern Recognition Receptor (PRR)

Innate immune sensor (e.g., TLR, NLR) that detects conserved microbial PAMPs and triggers defense signaling.

Toll-like Receptor (TLR)

Surface or endosomal PRR that recognizes specific microbial molecules and activates innate immunity.

NOD-like Receptor (NLR)

Cytoplasmic PRR detecting intracellular bacterial components to induce inflammatory responses.

RIG-I-like Receptor (RLR)

Cytoplasmic sensor that recognizes viral RNA and promotes interferon production.

Pathogen-Associated Molecular Pattern (PAMP)

Conserved microbial structure (e.g., LPS, flagellin) recognized by innate receptors.

Fever

Systemic rise in body temperature induced by pyrogens that inhibits microbes and boosts immunity.

Pyrogen

Substance (e.g., IL-1, LPS) that resets hypothalamic thermostat to elevate body temperature.

Antigen

Molecule capable of being recognized by adaptive immune receptors and eliciting a response.

Epitope

Specific antigenic determinant bound by an antibody or T-cell receptor.

Immunoglobulin (Antibody)

Y-shaped protein produced by plasma cells that binds antigens and mediates effector functions.

IgG

Most abundant antibody in serum; provides long-term immunity and crosses placenta.

IgM

Pentameric antibody produced first in a primary response; effective at agglutination and complement activation.

IgA

Dimeric antibody found in mucosal secretions (saliva, milk) that protects external surfaces.

IgE

Antibody class that binds mast cells and basophils, mediating allergic reactions and parasitic defense.

IgD

Membrane-bound antibody serving mainly as a B-cell receptor for antigen recognition.

Major Histocompatibility Complex Class I (MHC I)

Molecule on all nucleated cells that presents endogenous peptides to CD8⁺ cytotoxic T cells.

Major Histocompatibility Complex Class II (MHC II)

Molecule on professional APCs that presents exogenous peptides to CD4⁺ helper T cells.

TH1 Cell

CD4⁺ T-helper subset that activates macrophages and promotes cell-mediated immunity via IFN-γ.

TH2 Cell

CD4⁺ T-helper subset that stimulates B-cells and eosinophils, important for humoral and parasitic responses.

TH17 Cell

CD4⁺ T-helper subset producing IL-17 to recruit neutrophils against extracellular pathogens.

Regulatory T Cell (Treg)

T-cell subset that dampens immune responses and maintains self-tolerance.

Cytotoxic T Lymphocyte (CTL)

CD8⁺ T cell that kills infected or malignant cells using perforin and granzymes.

Plasma Cell

Terminally differentiated B cell specialized for mass antibody secretion.

Memory B Cell

Long-lived B cell formed after antigen exposure that mounts rapid, strong responses upon re-encounter.

Neutralization

Antibody function that blocks microbial attachment or toxin activity.

Antibody-Dependent Cell-Mediated Cytotoxicity (ADCC)

Killing of antibody-coated targets by NK cells or other leukocytes via Fc receptor engagement.

Primary Immune Response

Initial adaptive response to a new antigen, slow with predominant IgM production.

Secondary Immune Response

Faster, stronger adaptive response upon re-exposure characterized by high-affinity IgG/IgA and robust memory cell activation.

Type I Hypersensitivity

Immediate IgE-mediated allergic reaction leading to mast-cell degranulation and possible anaphylaxis.

Type II Hypersensitivity

Cytotoxic reaction where IgG/IgM bind cell surface antigens causing complement activation or ADCC.

Type III Hypersensitivity

Immune-complex disease where soluble Ag-Ab complexes deposit in tissues, provoking inflammation.

Type IV Hypersensitivity

Delayed, T-cell-mediated reaction appearing 24-72 h after antigen exposure (e.g., contact dermatitis, TB test).

Autoimmunity

Pathological immune response directed against self antigens due to loss of tolerance.

Immunodeficiency

State of impaired immune function leading to recurrent or severe infections.

Severe Combined Immunodeficiency (SCID)

Congenital absence of functional T and B cells, causing life-threatening infections early in life.

Acquired Immunodeficiency Syndrome (AIDS)

Advanced HIV infection marked by profound CD4⁺ T-cell loss and opportunistic diseases.

Anaphylaxis

Rapid, systemic Type I hypersensitivity reaction causing vasodilation, bronchospasm, and potential shock.

Sepsis

Life-threatening organ dysfunction from a dysregulated host response to bloodstream infection.

Infective Endocarditis

Microbial infection of heart valves/endocardium forming vegetations that damage valves and embolize.

Bacteremia

Presence of viable bacteria circulating in the bloodstream.

Pneumonia

Infection-induced inflammation of lung parenchyma, classified by setting and pathogen type.

Mycobacterium tuberculosis

Acid-fast bacillus causing tuberculosis with latent and active pulmonary or disseminated forms.

Neisseria gonorrhoeae

Gram-negative diplococcus causing urethritis, cervicitis, PID, and neonatal conjunctivitis; exhibits rising drug resistance.

Clostridioides difficile

Spore-forming anaerobe whose toxins A and B cause antibiotic-associated pseudomembranous colitis.

Rotavirus

Reovirus responsible for severe dehydrating diarrhea in children, preventable by oral vaccine.

Human Papillomavirus (HPV)

DNA virus causing warts and high-risk strains linked to cervical and other cancers; prevented by 9-valent vaccine.

Vector-Borne Disease

Infection transmitted by arthropods such as ticks, mosquitoes, or fleas (e.g., malaria, Lyme disease).