Immunology Exam 1

Immunology

Study of physiological mechanisms used to defend the body from foreign or infectious agents.

Immune system

Cells and molecules dedicated to defense against infection.

Innate immunity

Fixed, genetically determined immune defenses that respond rapidly and lack memory.

Adaptive immunity

Highly specific immune response that develops slowly and exhibits memory.

Primary immune response

First activation of the adaptive immune system against a specific pathogen.

Secondary immune response

Faster, stronger adaptive response upon re-exposure to the same pathogen.

Protective immunity

→ Immunity that prevents disease upon reinfection due to immune memory.

Immunological memory

→ Persistence of antigen-specific T and B cells after infection or vaccination.

Pathogen

→ Any organism with the potential to cause disease.

Opportunistic pathogen

→ Causes disease when host defenses are weakened or when entering abnormal sites.

Commensal organisms

→ Normal flora that live on/in the host without causing harm.

Normal flora

→ Microorganisms that normally inhabit the body and provide protection by competition.

Extracellular pathogen

→ Microbe that lives and replicates outside host cells.

Intracellular pathogen

→ Microbe that infects and replicates within host cells.

Vaccination

→ Exposure to weakened, killed, subunit, or RNA pathogen to induce immune memory.

Vaccine

→ Preparation that stimulates adaptive immunity without causing disease.

Vaccinia virus

→ Virus used by Jenner to protect against smallpox.

Variola virus

→ Virus that causes smallpox.

Physical barriers

→ Skin, hair, nails, and mucosal surfaces that block pathogen entry.

Mucosal surfaces (mucosae)

→ Vulnerable epithelial tissues lining respiratory, GI, and urogenital tracts.

Mucus

→ Thick fluid that traps microbes and contains antimicrobial enzymes.Lysozyme

Lysozyme

→ Antibacterial enzyme in tears and saliva that breaks down bacterial cell walls.

Defensins

→ Antimicrobial peptides that disrupt microbial membranes.

Inflammation

→ Innate immune response characterized by vasodilation, permeability, and leukocyte recruitment.

Vasodilation

→ Widening of blood vessels to increase blood flow.

Vascular permeability

→ Increased leakage of plasma proteins and leukocytes into tissues.

Complement system

→ Plasma protein cascade that tags or destroys pathogens.

Complement cascade

→ Sequential activation of complement proteins leading to pathogen elimination.

Membrane Attack Complex (MAC)

→ C5b–C9 complex that forms pores in pathogen membranes.

Zymogen

→ Inactive enzyme precursor requiring cleavage for activation.

Opsonin

→ Molecule that coats pathogens to enhance phagocytosis.

Alternative pathway

→ Complement pathway activated spontaneously without antibodies.

Lectin pathway

→ Complement pathway initiated by mannose-binding lectin (MBL).

Classical pathway

→ Complement pathway initiated by antibodies or C-reactive protein.

Tickover

→ Continuous low-level spontaneous hydrolysis of C3.

C3

→ Central complement protein cleaved into C3a and C3b.

C3a

→ Anaphylatoxin that promotes inflammation.

C3b

→ Anaphylatoxin that promotes inflammation.

C3 convertase (alternative)

→ C3bBb complex that cleaves C3.

C5 convertase (alternative)

→ C3b₂Bb complex that cleaves C5.

Properdin (Factor P)

→ Stabilizes C3bBb on microbial surfaces.

Factor D

→ Protease that cleaves factor B in the alternative pathway.

Anaphylatoxin

→ Complement fragments that promote inflammation.

C5a

→ Most potent anaphylatoxin; strong chemotactic factor.

Chemotaxis

→ Directed movement of immune cells toward a chemical signal.

Decay Accelerating Factor (DAF)

→ Host protein that disrupts C3 convertase on human cells.

Membrane Cofactor Protein (MCP)

→ Host protein that inactivates C3b.

CR1 (Complement Receptor 1)

→ Binds C3b; promotes phagocytosis and complement regulation.

CD59 (Protectin)

→ Prevents formation of MAC on host cells.

Factor H

→ Plasma protein that inactivates C3b on host-like surfaces.

Pentraxins

→ Soluble proteins that opsonize pathogens (e.g., CRP).

C-reactive protein (CRP)

→ Acute-phase protein that binds pathogens and activates classical complement.

Acute-phase response

→ Increase in innate immune proteins during infection.

Mannose-binding lectin (MBL)

→ Lectin that binds carbohydrates on pathogens.

MASP (MBL-associated serine protease)

→ Protease that initiates the lectin complement pathway.

Leukocyte

→ General term for white blood cell.

Lymphocyte

→ White blood cell involved in adaptive or innate immunity.

B cell

→ Lymphocyte that produces antibodies.

T cell

→ Lymphocyte that recognizes antigen presented by MHC.

NK cell

→ Innate lymphocyte that kills virus-infected and tumor cells.

Neutrophil

→ Most abundant leukocyte; phagocytic; major pus former.

Monocyte

→ Circulating precursor to macrophages.

Macrophage

→ Tissue phagocyte involved in innate and adaptive immunity.

Dendritic cell

→ Professional antigen-presenting cell that activates T cells.

Mast cell

→ Tissue cell that releases histamine during inflammation.

Eosinophil

→ Granulocyte that kills large parasites.

Basophil

→ Rare granulocyte involved in allergic responses.

Antigen

→ Molecule recognized by antibodies or T cell receptors.

Epitope

→ Specific portion of an antigen recognized by a receptor.

Antibody (Immunoglobulin)

→ Protein that binds antigen and mediates humoral immunity.

T-cell receptor (TCR)

→ Antigen receptor on T cells; recognizes peptide-MHC complexes.

MHC (Major Histocompatibility Complex)

→ Molecules that present antigen to T cells.

MHC I

→ Presents intracellular antigens; expressed on all nucleated cells.

MHC II

→ Presents extracellular antigens; expressed on professional APCs.

Primary lymphoid organs

→ Bone marrow and thymus.

Secondary lymphoid organs

→ Lymph nodes, spleen, MALT.

Lymph node

→ Site where lymph-borne antigens activate lymphocytes.

Draining lymph node

→ Lymph node receiving antigens from an infection site.

Spleen

→ Filters blood and initiates immune responses to blood-borne pathogens.

Red pulp

→ Removes old or damaged red blood cells.

White pulp

→ Immune response region of the spleen.

MALT

→ Mucosal-associated lymphoid tissue defending mucosal surfaces.