Topic 5: Responding to Antigens and Acquiring Immunity – Vocabulary Flashcards

Vocabulary flashcards covering key immunology terms from Topic 5: Responding to Antigens and Acquiring Immunity. Use these to practise recognising and recalling definitions for exam preparation.

Acquired immunity

Immunity that develops during a person’s lifetime.

Active immunity

Immunity produced when a person’s own immune system makes antibodies after exposure to an antigen.

Adaptive immunity

Specific immune response that develops through contact with a particular antigen.

Allergen

An antigen that triggers an allergic response.

Allergic response

Rapid immune reaction to harmless antigens, involving IgE production and histamine release.

Allergy

Abnormal immune response to substances harmless to most people.

Anaphylaxis

Acute, potentially lethal allergic reaction in a sensitised individual.

Antibodies

Proteins (immunoglobulins) made by plasma cells that bind specifically to the antigen that induced them.

Antigen-binding sites (variable regions)

Regions of an antibody molecule where antigens bind.

Antigen-presenting cells (APCs)

Immune cells that display antigens on MHC-II to activate helper T cells.

Antigens

Molecules that stimulate an immune response.

Artificial active immunity

Immunity gained by deliberate exposure to disabled antigens (e.g., vaccination).

Artificial passive immunity

Immediate immunity gained by administration of antibodies.

Artificial immunity

Immunity established through deliberate medical intervention.

Attenuated pathogen

Live pathogen treated so it can no longer cause disease but can elicit immunity.

Autoimmune diseases

Conditions in which the immune system attacks the body’s own tissues.

B lymphocytes (B cells)

White blood cells that recognise antigens and produce specific antibodies.

Bone marrow

Blood-forming tissue inside bones; site of B-cell maturation.

Capsid

Protein shell that encloses viral genetic material.

Cascade

Multi-step process where each step triggers the next in sequence.

Cell surface markers

Membrane proteins/glycoproteins that distinguish cell types and self from non-self.

Cell surface receptors

Trans-membrane regions that bind extracellular molecules for signalling.

Cell-mediated adaptive response

Specific response where cytotoxic T cells kill virus-infected cells.

Cell-mediated immunity

Immune response driven by immune cells rather than antibodies.

Cellular pathogens

Disease-causing agents composed of cells that reproduce independently.

Chemical barriers

Innate defences using enzymes or chemicals to kill pathogens.

Chemotaxis

Directed cell movement toward chemical signals such as cytokines.

Cilia

Hair-like membrane extensions that move in synchrony.

Clonal expansion

Rapid division of an antigen-specific lymphocyte to produce identical cells.

Clonal selection

Process in lymph nodes where lymphocytes with receptors for a new antigen are activated.

Clones

Groups of genetically identical cells, organisms or genes.

Complement proteins

Innate proteins that aid immune cells and can lyse bacteria.

Constant region

Antibody section that is identical within an antibody class.

Cytokines

Signalling molecules of the immune system.

Cytotoxic T cells

T cells that kill infected host cells using perforin and granzyme B.

Dendritic cells

Phagocytic APCs that activate T lymphocytes.

Degranulation

Release of chemicals (e.g., histamine) from immune cell granules.

Dermicidin

Antimicrobial protein secreted in sweat acting as a chemical barrier.

Endotoxins

Toxic parts of Gram-negative bacterial outer membrane released on cell death.

Enveloped viruses

Viruses surrounded by a host-derived membrane envelope.

Eosinophils

Granule-containing white blood cells that kill large parasites.

Extracellular

Located outside cells (e.g., blood plasma).

Exotoxins

Toxins secreted by microorganisms into their surroundings.

First line of defence

Innate barriers preventing pathogen entry.

Granzymes

Protease enzymes in NK and cytotoxic T cell granules that induce apoptosis.

Helper T cells

T cells that activate B cells and cytotoxic T cells via cytokines.

Histamine

Inflammatory mediator causing blood-vessel dilation and permeability.

Humoral immunity

Antibody-mediated immune response in body fluids.

Human leukocyte antigens (HLA)

Self antigens on human cell surfaces.

Immune system

Body system of specialised cells and proteins resisting infection.

Immunoglobulins

Antigen-binding proteins (antibodies) from B cells.

Immunoglobulin E (IgE)

Antibody class involved in allergic reactions.

Immunological memory

Ability of adaptive immunity to recall an antigen after first exposure.

Incubation period

Time between infection and first symptoms.

Inflammation

Innate reaction causing redness, heat, swelling at injury/infection.

Inflammatory response

Local redness and swelling due to increased blood flow from infection.

Innate immunity

Present from birth; fast, non-specific immune responses.

Interferons

Proteins secreted by virus-infected cells that help neighbours resist infection.

Intracellular

Located within a cell.

Leukocytes

White blood cells protective against infection.

Ligands

Molecules that bind specific targets to form active complexes.

Lymph

Interstitial fluid that enters the lymphatic system.

Lymph nodes

Lymphatic organs where adaptive immune responses are initiated.

Lymphatic system

Network of tissues/organs crucial to immune response.

Lysis

Destruction of cells by membrane rupture.

Lymphocytes

White blood cells (B, T, NK) involved in specific immunity.

Lysozyme

Enzyme in tears/saliva that breaks down bacterial walls.

Macrophages

Phagocytic APCs derived from monocytes; engulf pathogens.

Major histocompatibility complex (MHC)

Surface proteins identifying cells as ‘self’.

Mast cells

Histamine-containing immune cells involved in allergy and inflammation.

Membrane-attack complex (MAC)

Complement-derived structure that lyses pathogen membranes.

Memory cells

Long-lived lymphocytes poised for rapid re-activation.

MHC-I

MHC type on all nucleated cells.

MHC-II

MHC type on specific APC white blood cells.

Microbiological barriers

Innate defence via normal body flora.

Mucous membranes

Cellular linings of internal airways, gut, urogenital tract.

Mucus

Gel-like secretion from mucous membranes.

Naïve (immune cell)

Lymphocyte that has not yet been activated by antigen.

Natural active immunity

Immunity from antibody production after natural infection.

Natural immunity

Specific immunity acquired without medical intervention.

Natural killer (NK) cells

Innate lymphocytes that kill virus-infected cells.

Natural passive immunity

Immunity from naturally acquired antibodies (e.g., breastfeeding).

Neutralisation

Antibody binding that blocks toxins or pathogen surface antigens.

Neutrophils

Most abundant white blood cells; fast-acting phagocytes.

Non-enveloped (naked) viruses

Viruses lacking an outer membrane envelope.

Non-self antigens

Antigens not originating from the body’s own cells.

Opsonisation

Complement coating that enhances phagocytosis of pathogens.

Pathogen-associated molecular patterns (PAMPs)

Molecules unique to pathogens recognised as foreign.

Pathogens

Agents that cause disease in hosts.

Passive immunity

Short-term immunity obtained from external antibodies.

Pattern recognition receptor (PRR)

Phagocyte receptors that detect generic pathogen features.

Perforin

Protein that forms pores in target cell membranes during immune attack.

Phagocytes

White blood cells (e.g., neutrophils, macrophages) that engulf pathogens.

Phagocytosis

Cellular engulfment of solid particles into a phagosome.

Phagosome

Membrane vesicle enclosing an engulfed pathogen inside a phagocyte.

Physical barriers

Innate structures blocking pathogen entry (e.g., skin).

Plasma cells

Short-lived B cells that secrete large amounts of antibody.

Primary antibody response

Initial antibody production following first antigen exposure.

Primary lymphoid organs

Bone marrow and thymus where lymphocytes mature.

Prions

Infectious, nucleic-acid-free protein particles.