Immunology - Chapter 1: Basic Concepts in Immunology

A set of vocabulary flashcards defining key immunological terms and concepts from Chapter 1 of Janeway's Immunobiology.

Immunology

The study of the body's defense against infection at the cellular and molecular levels.

Vaccination

The procedure of inoculating healthy individuals with weakened or attenuated strains of disease-causing agents to provide protection from disease.

Adaptive immunity

A specific immune response against infection by potential pathogens that develops during the lifetime of an individual as an adaptation to infection with that pathogen.

Innate immunity

Nonspecific host defense mechanisms mediated by always-present phagocytic cells, anatomic barriers, and chemical systems that provide immediate or rapid defense against infection.

Antibodies

Proteins present in serum that bind specifically to toxins or pathogens and neutralize their activity or target them for destruction.

Complement

A group of around 30 plasma proteins that act in conjunction with antibodies or independently to lyse bacteria, mark pathogens for phagocytosis, and trigger inflammation.

Antigen

Any substance recognized by the adaptive immune system, typically common proteins, glycoproteins, and polysaccharides of pathogens.

Commensal microorganisms

Microorganisms that constantly colonize host tissues (such as skin and gut mucosa) in a symbiotic relationship without causing host damage.

Effector mechanisms

Molecular and cellular functions of the immune system that act to resist, eliminate, or destroy different categories of pathogens; also called mediators.

Immunological tolerance

Mechanisms that prevent an immune response from being mounted against the host's own tissues.

Pattern Recognition Receptors (PRRs)

Invariant innate recognition receptors expressed by sensor cells that detect simple molecular structures common to pathogens (PAMPs) or cellular damage.

Pathogen-Associated Molecular Patterns (PAMPs)

Simple, conserved molecular structures and regular patterns expressed by many microorganisms (such as bacterial lipopolysaccharides or peptidoglycans) but absent from host cells.

Cytokines

Proteins secreted by immune cells that affect the behavior of nearby target cells bearing appropriate receptors to amplify immune responses.

Chemokines

A specialized subgroup of secreted chemoattractant proteins that attract cells bearing chemokine receptors out of the bloodstream into infected tissues and organize cells within lymphoid tissues.

Inflammation

A local response to infection or tissue injury characterized by heat (calor), pain (dolor), redness (rubor), and swelling (tumor), caused by vasodilation, increased vascular permeability, and recruitment of leukocytes.

Natural Killer (NK) cells

Large granular innate lymphocytes that lack antigen-specific receptors and respond to cellular stress or viral infections by releasing lytic granules to kill infected or tumor cells.

Innate Lymphoid Cells (ILCs)

Tissue-resident innate lymphocytes derived from the common lymphoid progenitor that lack antigen-specific receptors and secrete specific patterns of cytokines upon activation.

Naive lymphocytes

Lymphocytes that have completed maturation in primary lymphoid organs but have not yet encountered their specific antigen.

Effector lymphocytes

Functional lymphocytes that have encountered their specific antigen, become activated, and differentiated to carry out immune elimination functions.

Epitope

The small portion of an antigen's molecular structure recognized and bound by an individual antigen receptor or antibody; also called an antigenic determinant.

Major Histocompatibility Complex (MHC)

A cluster of genes encoding cell-surface glycoproteins (MHC class I and class II) that present peptide fragments of degraded proteins to T-cell receptors.

Clonal selection theory

The central principle of adaptive immunity stating that each lymphocyte bears a single type of antigen receptor with unique specificity, and binding to its specific antigen activates the cell to proliferate into a clone of identical effector cells.

Clonal deletion

The removal of potentially self-reactive developing lymphocytes by programmed cell death (apoptosis) before they mature, ensuring immunological self-tolerance.

Central lymphoid organs

The primary organs (bone marrow and thymus) where lymphocytes are generated and undergo initial development and maturation.

Peripheral lymphoid organs

The secondary tissues (lymph nodes, spleen, and MALT) where mature naive lymphocytes congregate, encounter antigen, and initiate adaptive immune responses.

High endothelial venules (HEV)

Specialized blood vessels in lymph nodes lined by rounded endothelial cells through which circulating lymphocytes migrate from the blood into the lymph node parenchyma.

Germinal centers

Central areas within lymphoid follicles where activated B cells undergo intense proliferation and differentiation into antibody-secreting plasma cells.

Microfold (M) cells

Specialized epithelial cells overlying mucosal lymphoid tissues (such as Peyer's patches) that collect and transport antigens from the intestinal or respiratory lumen to underlying immune cells.

Neutralization

The protective function of antibodies in which binding to a virus or bacterial toxin blocks its ability to enter cells or bind target receptors.

Opsonization

The coating of pathogens or foreign particles with antibodies or complement fragments to facilitate their recognition and uptake by phagocytes.

Cytotoxic T cells

CD8-bearing effector T lymphocytes that recognize peptides presented on MHC class I molecules and directly kill virus-infected cells.

Helper T cells

CD4-bearing effector T lymphocytes that recognize peptides presented on MHC class II molecules and secrete cytokines that activate B cells, macrophages, or other immune cells.

Type 1 immunity

An effector module driven by ILC1 and TH1 cells that produces interferon-$\gamma$ (IFN-$\gamma$) to activate macrophages and combat intracellular pathogens.