Innate Immunity and Fundamental Immunology

Vocabulary practice flashcards based on innate immunity, leukocyte migration, complement pathways, historical immunology, and macrophage biology.

Innate Immune System

The first line of host defense present at most tissue sites that recognizes broad classes of pathogens; it comprises both cellular components (such as macrophages and neutrophils) and humoral factors (such as complement).

Macrophages

Innate phagocytic immune cells that engulf pathogens and present antigens to other components of the immune system.

Normal Gut Flora

The community of mostly commensal microorganisms inhabiting a healthy gut that prevents infection by occupying available physical niches, but can become opportunistic pathogens when host immunity fails.

M2 Macrophages

Tissue-repairing macrophages ('healers') that, within the tumor microenvironment, often suppress immune responses, facilitate cancer cell survival, and promote tumor growth.

Natural Killer (NK) Cells

Innate lymphoid cells that eliminate intracellular pathogens by detecting stressed, infected, or malignant host cells and inducing their apoptosis.

E-selectin

An endothelial adhesion molecule upregulated during inflammation that binds to sialyl-Lewisx on leukocytes to mediate weak, transient tethering and rolling.

Sialyl-Lewisx

A carbohydrate ligand expressed on leukocytes that binds endothelial E-selectin, facilitating leukocyte rolling along the vascular endothelium.

ICAM-1

An adhesion molecule on vascular endothelial cells that binds to leukocyte integrins to mediate firm adhesion and arrest during extravasation.

Leukocyte Extravasation Cascade

The sequential multi-step recruitment of leukocytes from blood into tissue consisting of selectin-mediated rolling, chemokine activation of integrins, integrin-mediated firm adhesion, and diapedesis.

Diapedesis

The transendothelial migration step wherein leukocytes traverse the vascular endothelial wall to enter inflamed tissues following firm adhesion.

KIR (Killer Cell Inhibitory Receptor)

An NK cell surface receptor that recognizes MHC class I on healthy target cells to deliver inhibitory signals that prevent cytotoxic killing.

KAR (Killer Cell Activating Receptor)

An NK cell surface receptor that detects stress-induced ligands on target cells, triggering cytotoxic killing when unopposed by inhibitory signals.

Missing-Self Recognition

The process by which an NK cell detects and destroys target cells lacking normal MHC I expression due to the loss of inhibitory KIR signaling.

C3 Cleavage

The central enzymatic step of the complement cascade in which C3 is cleaved into fragments C3a and C3b across the classical, lectin, and alternative pathways.

Alternative Complement Pathway

The fastest-activating pathway of the complement cascade that rapidly targets pathogens.

Classical Complement Pathway

The slowest-activating pathway of the complement system, which is typically triggered by antibody binding to antigens.

TNF-α Systemic Shock

A severe clinical condition caused by widespread systemic release of TNF-α, resulting in extensive vascular plasma leakage, precipitous drops in blood pressure, and decreased organ perfusion.

Type I Interferon Pretreatment

The administration of type I interferons prior to viral infection that upregulates interferon-stimulated genes, primes the innate response, and accelerates viral clearance.

Variolation

An early method of immunization against smallpox involving the transfer of infectious material directly from smallpox lesions, which conferred immunity but carried a high risk of severe illness or death.

Vaccination (Jennerian)

An immunization strategy pioneered by Edward Jenner using less virulent cowpox virus to safely induce cross-protective immunity against smallpox.

Cluster of Differentiation (CD) System

A standardized nomenclature system comprising over 370 markers established to identify and categorize cell surface proteins across diverse immune cell types.

Vascular Hemodynamics in Local Inflammation

The inflammatory response characterized by blood vessel dilation, which increases vessel permeability and decreases blood flow velocity to facilitate immune cell recruitment into tissues.

Mycobacterium tuberculosis Phagosomal Evasion

An intracellular persistence mechanism wherein bacteria avoid lysosomal degradation by preventing the fusion of endosomes with lysosomes into phagolysosomes within macrophages.

TLR3 and MDA5

Pattern recognition receptors specialized in sensing long double-stranded viral RNA (dsRNA).

RIG-I

A cytosolic pattern recognition receptor specialized in detecting short double-stranded viral RNA (dsRNA).

Koch's Postulates

A series of reproducible experimental criteria used to definitively prove that a specific microorganism causes a specific disease by isolating, culturing, and transmitting the pathogen.

Louis Pasteur

The scientist whose pioneering research on microbial attenuation laid the foundational framework for developing attenuated vaccines.

Trained Innate Immunity

A state of heightened innate immune memory driven by epigenetic reprogramming (e.g., following β-glucan exposure) that amplifies subsequent cytokine production upon restimulation by unrelated pathogens.

Kupffer Cells

Liver-resident macrophages specialized in clearing systemic toxins and filtering blood, demonstrating tissue-specific functional adaptation of innate immune cells.

Microglia

Brain-resident macrophage-like cells specialized in maintaining neural homeostasis and responding to tissue injury within the central nervous system.