2 Immunology I - Fundamental Concepts and Innate Immunity

Vocabulary flashcards covering core concepts of immunology, immune cells, recognition mechanisms, and innate defense pathways based on Ross University School of Veterinary Medicine lecture notes.

Immune system

A system of organs, cells, tissues, and molecules that facilitate resistance against foreign or danger elements (antigens).

Immune response

A coordinated reaction of the immune system in response to antigens.

Inflammatory response

A coordinated reaction of the immune system in response to danger signals.

Immunology

The discipline that studies the immune system, including its structure, organization, function, and evolution.

Antigen

A molecule or structure that can be recognized by immune system receptors, producing a specific reaction by cells or antibodies.

Immunogen

An antigen that is recognized by the body as non-self and stimulates an immune response.

Epitope

The specific, smallest region of an antigen that is recognized and bound by an antibody or an immune cell receptor (BCR or TCR) on lymphocytes.

Innate immunity

An antigen-independent arm of defense with broad specificity and minimal memory that responds immediately (minutes to hours) using physical barriers, phagocytes, complement, and inflammation.

Adaptive immunity

An antigen-dependent arm of defense with high specificity for specific epitopes and significant memory that generates a delayed response (days to weeks) via T lymphocytes, B lymphocytes, and antibodies.

Humoral immunity

Immunity mediated by macromolecules in solution found in extracellular fluids (body fluids/humors), such as complement, antimicrobial peptides, and antibodies.

Cellular immunity

Immunity involving various cells that participate directly in the immune response, including macrophages, dendritic cells, neutrophils, mast cells, NK cells, B cells, and T cells.

Neutrophils

Polymorphonuclear granulocytes with multilobed nuclei and neutral (slightly pink) granules that provide antimicrobial defense (especially during acute bacterial infections) via phagocytosis, degranulation, and NET formation.

Heterophils

Antimicrobial granulocytes found in birds and reptiles instead of neutrophils that perform immune defense and form heterophil extracellular traps (HETs).

Eosinophils

Granulocytes with lobed nuclei and prominent pink-to-red (eosinophilic) granules that participate in defense against parasites (helminths) and in allergic reactions.

Eosinophilia

An increase in the number of eosinophils in peripheral blood, commonly associated with helminth parasite infections or allergic responses.

Basophils

Granulocytes with a bilobed nucleus and large purple (basophilic) granules involved in allergic reactions, inflammation, and defense against parasites.

Mast cells

Tissue sentinel cells containing prominent secretory granules that release vasoactive amines (histamine, serotonin), lipid mediators, and cytokines to induce vasodilation, increase vascular permeability, and amplify inflammation.

Macrophages

Large mononuclear cells derived from monocytes that function in immune surveillance, antimicrobial phagocytosis, release of inflammatory mediators, tissue repair, and limited antigen presentation.

Dendritic cells

Specialized antigen-presenting cells that capture, process, and present antigens to T lymphocytes, bridging innate and adaptive immune responses.

Natural Killer (NK) cells

Innate lymphocytes that identify virus-infected or abnormal/mutated host cells exhibiting reduced MHC Class I expression and release cytotoxic lytic granules to induce apoptosis.

Cytokines

Small proteins that signal cells to engage in functions such as cell growth, activation, differentiation, and polarization.

Interleukins

A class of cytokines that function specifically in communication between white blood cells and other immune cells.

Chemokines

A class of cytokines that induce chemotaxis, directing cell movement toward chemical signals.

Pathogen-Associated Molecular Patterns (PAMPs)

Conserved molecular structures shared by groups of pathogens (or microbes/MAMPs) that are distinct from host self-molecules and recognized as non-self.

Damage-Associated Molecular Patterns (DAMPs)

Endogenous molecules released by damaged, injured, or necrotic host cells (or extracellular matrix breakdown) that signal danger to initiate inflammation.

Pattern Recognition Receptors (PRRs)

Molecules located on the cell surface, inside endosomes/phagolysosomes, or in the cytosol of host cells that bind PAMPs and DAMPs to induce innate immune responses.

Phagocytosis

The process by which specialized phagocytes (neutrophils, macrophages, dendritic cells) engulf and ingest large particles such as bacteria, dead cells, or debris into a phagosome for destruction.

Phagolysosome

A cytoplasmic body formed by the fusion of a phagosome (containing an ingested microbe) with a lysosome, exposing the pathogen to oxidative and enzymatic killing mechanisms.

Respiratory burst

An oxygen-dependent intracellular killing mechanism in phagocytes characterized by a sudden increase in oxygen and glucose consumption to produce Reactive Oxygen Species (ROS) and Reactive Nitrogen Species (RNS).

Complement System

A collection of over 30 circulating plasma proteins and membrane proteins that circulate as inactive zymogens and activate in a cascade sequence to mediate opsonization, inflammation, and cell lysis.

Classical pathway

A complement activation pathway triggered by antigen-antibody complexes (IgG or IgM bound to antigen).

Lectin pathway

A complement activation pathway triggered when carbohydrate-binding plasma proteins, such as mannose-binding lectin (MBL), bind to microbial carbohydrates.

Alternative pathway

A complement activation pathway triggered spontaneously on microbial surfaces due to the absence of host regulatory proteins, operating independently of antibodies.

Membrane Attack Complex (MAC)

A structure formed by complement proteins C5b, C6, C7, C8, and multiple C9 molecules that inserts into microbial cell membranes, creating cylindrical pores that induce osmotic lysis.