Chapter 1: Elements of the Immune System and Their Roles in Defense - Vocabulary Flashcards

100 vocabulary-style flashcards covering key concepts from Chapter 1 notes on the immune system.

Immunology

The study of the physiological mechanisms by which humans defend against infection.

Microorganisms

Microscopic organisms that can cause infectious disease and reproduce rapidly.

Innate immunity

The immediate, non-specific first line of defense, including barriers and rapid responses.

Adaptive immunity

Pathogen-specific immune response that develops with exposure and provides memory.

Commensal microorganisms

Microbes that normally inhabit the body without causing disease and can benefit the host.

Microbiota

The entire community of microorganisms living in or on the body.

Gut microbiota

Microbiota specifically in the gastrointestinal tract.

Escherichia coli (E. coli)

A major gut bacterium that can secrete colicins to limit other bacteria.

Clostridium difficile

An opportunistic gut bacterium that can cause severe diarrhea after antibiotics.

Pathogen

An organism that causes disease.

Viruses

A class of pathogens consisting of genetic material inside a protein coat.

Bacteria

Prokaryotic microorganisms; can be Gram-positive or Gram-negative.

Fungi

Eukaryotic pathogens such as Candida; can cause disease.

Parasites

Protozoa and helminths that infect hosts.

SARS-CoV-2

Coronavirus responsible for the disease COVID-19.

Vaccination

Deliberate exposure to an agent to provoke protective immunity.

Smallpox

A viral disease eradicated by vaccination; caused by variola virus.

Jenner

Edward Jenner; pioneered vaccination with cowpox to prevent smallpox.

Vaccinia

Mild poxvirus used in early vaccines.

Variola major/minor

Strains of the smallpox virus; major caused more severe disease.

Mucosa

Mucosal surfaces lining the GI, respiratory, and urogenital tracts.

Skin barrier

The keratinized outer epithelium that blocks entry of pathogens.

Epithelia

Tissues that line surfaces and cavities; include skin and mucosa.

Goblet cells

Mucus-secreting cells in mucosal epithelia.

Cilia

Hair-like projections that move mucus out of the airways.

Lysozyme (tears and saliva)

Enzyme that kills bacteria by breaking down their cell walls.

Sebum

Sebaceous secretions with fatty acids that inhibit bacterial growth.

Antimicrobial peptides

Small peptides (e.g., defensins) that disrupt microbial membranes.

Endothelium

Layer lining blood vessels; regulates permeability.

Pattern-recognition receptors

Innate immune receptors that recognize conserved pathogen features.

Complement system

Plasma proteins that tag or kill pathogens and bridge innate/adaptive immunity.

Phagocytes

Cells that ingest and destroy microbes: neutrophils, macrophages, dendritic cells.

Phagocytosis

Engulfment and digestion of microbes by phagocytes.

Phagosome

Internal vesicle containing ingested material inside a phagocyte.

Phagolysosome

Vesicle formed by fusion of phagosome with lysosome; digestion occurs.

Cytokines

Small secreted proteins that regulate immune responses; include interleukins.

Vasodilation

Expansion of blood vessels during inflammation to increase blood flow.

Edema

Swelling caused by fluid accumulation during inflammation.

Inflammation

Local tissue response with heat, redness, swelling, and pain.

Inflammatory cells

White blood cells recruited to inflamed tissue.

Lymphocytes

White blood cells including B cells, T cells, NK cells, and ILCs.

B cells

Lymphocytes that produce antibodies and express BCR.

T cells

Lymphocytes that orchestrate cell-mediated immunity and express TCR.

B-cell receptor

Membrane-bound immunoglobulin on B cells that binds antigen.

Immunoglobulin

Antibody; the antigen-binding protein of the B-cell receptor.

Antibody

Secreted immunoglobulin that binds antigen and neutralizes pathogens.

T-cell receptor

Antigen receptor on T cells; can be αβ or γδ; recognizes peptide antigens with MHC.

Plasma cell

Differentiated B cell that secretes antibodies.

Antigen

Molecule or part of a molecule recognized by an antibody or MHC.

Epitope

Part of an antigen that interacts with an antibody or binds to an MHC-peptide complex.

Major histocompatibility complex (MHC)

Highly polymorphic molecules presenting peptides to T cells.

MHC class I

MHC class I presents endogenous peptides to CD8 T cells.

MHC class II

MHC class II presents exogenous peptides to CD4 T cells.

CD8

Co-receptor on cytotoxic T cells; binds to MHC class I.

CD4

Co-receptor on helper T cells; binds to MHC class II.

TH1

CD4+ subset activating macrophages; IFN-γ production.

TH2

CD4+ subset promoting antibody production and eosinophil responses.

TH17

CD4+ subset producing IL-17; promotes neutrophil responses.

TFH

T follicular helper cells; help B cells in germinal centers.

Treg

Regulatory T cells; suppress immune responses to prevent damage.

NK cells

Natural killer cells; cytotoxic lymphocytes of innate immunity.

ILC1/ILC2/ILC3

Innate lymphoid cells; tissue-resident counterparts to TH subsets.

Germinal center

Region within lymphoid follicles where B cells proliferate and mutate.

Lymph node

Secondary lymphoid organ where lymphocytes encounter antigens.

Spleen

Secondary lymphoid organ that filters blood; contains white and red pulp.

GALT

Gut-associated lymphoid tissue; includes tonsils, Peyer’s patches, appendix, etc.

MALT

Mucosa-associated lymphoid tissue; includes GALT and BALT.

Tonsils

Lymphoid tissue in the pharynx guarding the airway.

Adenoids

Mucosa-associated lymphoid tissue in the nasal cavity.

Appendix

Gut-associated lymphoid tissue in the beginning of the colon.

Peyer’s patches

Organized lymphoid tissue in the ileum sampling gut antigens.

M cells

Specialized mucosal cells delivering antigens to underlying lymphoid tissue.

Lymphatics

Lymphatic vessels that transport lymph.

Lymphocyte recirculation

Naive lymphocytes move between blood, lymph, and lymphoid tissues.

Primary lymphoid tissues

Bone marrow and thymus; sites of lymphocyte development.

Secondary lymphoid tissues

Lymph nodes, spleen, mucosal lymphoid tissues where responses are initiated.

Bone marrow

Primary site of hematopoiesis; produces blood cells.

Thymus

Primary lymphoid organ where T cells mature.

Hematopoiesis

Generation of all blood cells from hematopoietic stem cells.

Hematopoietic stem cell

Pluripotent stem cell giving rise to all blood cell lineages.

Megakaryocytes

Large bone marrow cells that give rise to platelets.

Platelets

Small cytoplasmic fragments essential for blood clotting.

Erythrocytes

Red blood cells responsible for oxygen transport.

Monocytes

Blood precursors of macrophages; circulate in blood.

Macrophages

Large phagocytes in tissues; APCs; secrete cytokines.

Dendritic cells

Professional antigen-presenting cells that activate T cells.

Mast cells

Tissue-resident cells with granules; mediators of allergy.

Eosinophils

Granulocytes defending against parasites and involved in allergies.

Neutrophils

Most abundant leukocytes; first responders; phagocytose.

Basophils

Rarest granulocytes involved in parasitic defense and allergy.

Opsonization

Coating pathogens with antibodies or complement to enhance phagocytosis.

Humoral immunity

Antibody-mediated immune responses.

Humors

Old term for body fluids containing antibodies.

Neutralization

Antibodies block pathogen or toxin function.

Complement activation

Activation of complement leading to pathogen killing and opsonization.

Antigen presentation

Display of peptide antigens by MHC to T cells.

Primary immune response

Initial adaptive response after first exposure to antigen; slower.

Secondary immune response

Faster, stronger response upon re-exposure due to memory.

Somatic hypermutation

Mutations in Ig variable regions during B cell maturation increasing diversity.

Isotype switching

Class switch recombination changing antibody isotype (e.g., IgM to IgG).