Innate immunity

49 topics with concise breakdowns: definitions, key facts, and class questions.

This section is dedicated to the body's first line of defense — innate immunity. Here, we examine myeloid cell differentiation and the work of primary tissue "guardians": macrophages, neutrophils, eosinophils, mast cells, and dendritic cells. You will study the molecular vision of immunity — pattern-recognition receptors (including Toll-like and C-type lectin receptors) that respond to foreign PAMPs and endogenous danger signals.

Special attention is paid to the dynamics of inflammation and pathogen destruction. We consistently analyze leukocyte migration (the role of selectins, integrins, and chemotaxis), the stages of phagocytosis, and powerful microbicidal mechanisms: from inflammasome assembly to oxygen-dependent pathways and degranulation. Natural killer (NK) cells are also described in detail — their receptor apparatus, functions, and cytotoxicity mechanisms.

Commonly asked in classes and exams: Instructors will certainly require knowledge of Toll-like receptor signaling pathways and complement system cascades. Students traditionally struggle with the cytokine network: it is crucial to clearly understand the functions of interleukins (IL-1, IL-6, IL-12), tumor necrosis factor alpha, interferons, and chemokines. Without a firm grasp of these topics, it is impossible to understand how innate immunity triggers and directs adaptive immunity.

Section Topics

Myeloid cell differentiationMyeloid cells are classical effectors of innate immunity, c NeutrophilsNeutrophilus Receptors of innate immune cellsInnate immune cells — neutrophils, eosinophils, and monocytes — do Myeloid cell granulesMyeloid cell granules are specialized intracellular organ EosinophilsEosinophilus Mast cells and basophilsMastocytus Macrophages and monocytesMacrophagocytus Dendritic cellsDendritic cells are professional antigen-presenting cells PAMP recognition and pattern-recognition receptorsPAMP recognition is an evolutionarily ancient and fundamental mechan Toll-like receptorsToll-like receptors (TLRs) are evolutionarily ancient structures of the syst Scavenger receptors and C-type lectin receptorsScavenger receptors and C-type lectin receptors are Cytoplasmic pattern-recognition receptorsCytoplasmic pattern-recognition receptors are intracellular Toll-like receptor signaling pathwaysToll-like receptors (TLRs) are the main "sensors" of innate immuni InflammasomeThe inflammasome is a cytosolic supramolecular protein complex responsible Macrophage activationMacrophage activation is the process of mobilizing the defense mechanisms of myel Endogenous danger signalsEndogenous danger signals (alarmins) are proprietary intracellular Leukocyte migration to the focus of inflammationLeukocyte migration is the directed exit of innate immune cells Selectins and their ligandsSelectins and their binding molecules (ligands) play a central IntegrinsIntegrins are transmembrane heterodimeric molecules that provide ChemotaxisChemotaxis is the directed movement of cells along a concentration gradient ChemokinesChemokines are small proteins (8–12 kDa in mass) that control PhagocytosisPhagocytosis is the cellular process of capturing and engulfing large particles Fc receptorsMembrane Fc receptors are specialized proteins on the surface of Receptors for complement componentsReceptors for complement components are specialized protein Oxygen-independent microbicidal factorsOxygen-independent microbicidal factors are a group of pre-existing Oxygen-dependent microbicidal mechanismsOxygen-dependent microbicidal mechanisms are a cascade of biochemical Nitrogen pathway of microbicidal substance formationThe nitrogen pathway is one of the most important biochemical mechanisms for destroying Antimicrobial peptides and enzymesAntimicrobial peptides and enzymes are key factors of innate immuni Neutrophil degranulationNeutrophil degranulation is the process of releasing the contents of intra Secretory function of macrophages and monocytesThe secretory function of macrophages and monocytes is a crucial mechanism for regulat Myeloid cell cytotoxicityMyeloid cell cytotoxicity is the ability of monocytes, macrophag Natural killer cellsNatural killer cells (NK cells) are large lympho NK cell receptorsNatural killer (NK) cell receptors are structures on the surfac Functions and activation of NK cellsNatural killer (NK) cells specialize in destroying infect NK cell cytotoxicityNatural killer cytotoxicity is the process of contact-mediated destructi Lymphokine-activated killer cellsLymphokine-activated killer (LAK) cells are a population of cytotoxic Complement systemThe complement system is a complex humoral cascade of innate immun Acute-phase proteinsAcute-phase proteins (acute-phase reactants) are a group of serum prote Biogenic aminesHistaminum EicosanoidsEicosanoids are an extensive group of humoral factors of innate immun CytokinesCytokines are protein and polypeptide molecules that provide Cytokine receptorsCytokine receptors are cell membrane protein structures responsi Cytokine networkThe cytokine network is a complex system of multiple cross-interact Interleukin-1Interleukin-1 (IL-1) is a key pro-inflammatory cytokine responsibl Tumor necrosis factor alphaTumor necrosis factor alpha is a key pro-inflammatory cytokine.Interleukins 6 and 12Interleukins 6 and 12 are key regulatory molecules of the immune system.Colony-stimulating factorsColony-stimulating factors (CSFs) are a specialized group of cyto InterferonsInterferons are cytokines that play a key role in innate immuni Immunological receptorsImmunological receptors are specialized molecular structur

Frequently asked questions for this section

What is the difference between the common myeloid progenitor (CMP) and the common lymphoid progenitor (CLP)?

The common myeloid progenitor (CMP) lacks the IL-7 receptor (IL-7Rα), which is characteristic of the lymphoid lineage. Also, the CMP is distinguished by the absence of the Sca-1 marker present on original stem cells.

How long do neutrophils live in tissues?

Their duration of stay in tissues ranges from 3 to 5 days, after which they undergo spontaneous apoptosis.

Which immunoglobulin receptors are found exclusively on eosinophils?

Among the cells considered, only eosinophils carry receptors for immunoglobulin E—FcεRI and FcεRII—on their surface.

What markers distinguish azurophilic granules from others?

The main markers of primary (azurophilic) granules are the enzyme myeloperoxidase and the membrane molecule CD63.

What is the difference between eosinophils, basophils, and mast cells?

Eosinophils and basophils circulate in the blood, whereas mast cells reside exclusively in tissues. Eosinophils target and destroy parasites, but their proteins can also activate basophils and mast cells during allergies.

Why do mast cells trigger allergies faster than basophils?

Mast cells are permanently stationed in skin and mucosal tissues, making them the first to encounter allergens. Basophils, on the other hand, reside in the blood and require additional time to migrate to the site of inflammation.

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