Week 1 Tutorial – Introduction to the Immune System: Vocabulary Flashcards

A comprehensive set of vocabulary flashcards covering foundational terms, cells, molecules, and processes discussed in the Week 1 Introduction to the Immune System tutorial.

Immunity

The ability of an organism to resist infection.

Innate Immune System

Branch of immunity that provides a rapid, non-specific response using physical, chemical, and cellular barriers; no memory formed.

Adaptive Immune System

Slower, antigen-specific branch of immunity that generates immunological memory and produces antibodies and cytotoxic responses.

Primary Lymphoid Organs

Bone marrow and thymus—sites where lymphocytes develop and mature (B cells in marrow, T cells in thymus).

Secondary Lymphoid Organs

Lymph nodes, spleen, and mucosa-associated lymphoid tissue (MALT) where mature lymphocytes are activated by antigens.

Pattern Recognition Receptor (PRR)

Receptor on innate immune cells that detects pathogen-associated molecular patterns (PAMPs).

Pathogen-Associated Molecular Pattern (PAMP)

Conserved microbial structures (e.g., LPS, LTA, bacterial DNA) recognized by PRRs.

Toll-Like Receptor (TLR)

Major family of PRRs that trigger innate immune signalling upon PAMP binding.

C-Type Lectin Receptor (CLR)

PRR family that binds carbohydrate structures on pathogens.

NOD-Like Receptor (NLR)

Intracellular PRRs that sense cytosolic PAMPs and danger signals.

RIG-I-Like Receptor (RLR)

Cytosolic PRRs that recognize viral RNA.

AIM2-Like Receptor (ALR)

PRRs detecting cytosolic DNA to activate inflammasome responses.

Cytokine

Small protein mediator secreted by cells to regulate immunity, inflammation, and hematopoiesis (e.g., TNF, IL-1).

Autocrine Signalling

Cytokine acts on the same cell that secreted it.

Paracrine Signalling

Cytokine acts on nearby cells.

Endocrine Signalling

Cytokine enters circulation to act on distant cells.

Chemokine

Subclass of cytokines that direct cell migration (e.g., CXCL8 attracts neutrophils).

Complement System

Plasma protein cascade that opsonises pathogens, forms membrane attack complexes, and generates inflammatory fragments.

Opsonisation

Coating of a pathogen with molecules (e.g., complement, antibodies) to enhance phagocytosis.

Membrane Attack Complex (MAC)

Complement end-product that forms pores and lyses target cells.

Anaphylatoxin

Complement fragment (e.g., C3a, C5a) that promotes inflammation and recruits immune cells.

Major Histocompatibility Complex (MHC)

Cell-surface proteins that present peptide antigens to T cells.

MHC Class I

MHC molecules on all nucleated cells presenting endogenous peptides to CD8⁺ T cells.

MHC Class II

MHC molecules on professional antigen-presenting cells presenting exogenous peptides to CD4⁺ T cells.

Phagocytosis

Engulfment and destruction of particles or microbes by cells such as macrophages and neutrophils.

Antigen Presentation

Display of processed peptide–MHC complexes to T cells to activate adaptive immunity.

Apoptosis

Programmed cell death that removes unwanted or infected cells without inflammation.

Myeloid Cells

Innate-immune lineage including dendritic cells, neutrophils, basophils, eosinophils, and macrophages.

Lymphoid Cells

Adaptive lineage (B cells, T cells) plus innate NK cells.

Macrophage

Phagocytic myeloid cell that engulfs pathogens and presents antigens; major producer of cytokines.

Neutrophil

Short-lived phagocytic granulocyte rapidly recruited to infection sites.

Eosinophil

Granulocyte involved in parasite defence and allergic inflammation; can release cytotoxic granules.

Basophil

Circulating granulocyte that releases histamine and mediators of acute inflammation.

Mast Cell

Tissue-resident granulocyte that releases histamine; key in allergic reactions and inflammation.

Natural Killer (NK) Cell

Innate lymphocyte that induces apoptosis in virus-infected or tumor cells.

B Cell

Lymphocyte that differentiates into plasma cells to produce antibodies; can act as an antigen-presenting cell.

Plasma Cell

Antibody-secreting effector form of a B cell.

T Helper (CD4⁺) Cell

T cell subset that coordinates immune responses, activating B cells and other immune cells via cytokines.

Cytotoxic T (CD8⁺) Cell

T cell subset that kills infected or malignant cells via perforin and granzymes.

Antibody (Immunoglobulin)

Y-shaped protein produced by B/plasma cells that binds specific antigens.

IgM

Pentameric antibody produced first in primary response; excellent at complement activation and opsonisation.

IgG

Most abundant serum antibody; dominates secondary responses; neutralises, opsonises, and fixes complement.

IgA

Dimeric antibody on mucosal surfaces; neutralises pathogens and toxins without strong inflammation.

IgD

Membrane-bound antibody on naïve B cells; role linked to B-cell activation and immune homeostasis.

IgE

Antibody involved in allergic reactions and defence against parasites; binds Fcε receptors on mast cells and basophils.

Cytokine vs. Chemokine

Cytokines are broad immune signalling proteins; chemokines are a subtype directing cell migration.

Skin Physical Barrier

Epidermal layer with tight junctions blocking pathogen entry.

Antimicrobial Peptides (AMPs)

Small peptides (e.g., LL-37, β-defensins) produced by skin and other tissues that directly kill microbes.

Interferon-Stimulated Genes (ISGs)

Genes induced by interferons that create an antiviral state (e.g., OAS2 in skin).

Opsonin

Any molecule (antibody, complement C3b) that enhances phagocytosis by marking a pathogen.

Inflammation

Localized protective response characterized by redness, heat, swelling, pain, and loss of function.