62 Questions
Which enzyme cascade is involved in the complement system activation?
Complement
What are the main chemical mediators involved in inflammation?
Prostaglandins, Leukotrienes, Histamine
Which type of immunity is primarily associated with Toll-like receptors and Pattern Recognition Receptors?
Innate Immunity
What is the function of chemokines in inflammation?
Attract immune cells to the site of infection or injury
Which type of immunity involves four main types of defensive barriers/mechanisms including anatomical and physiological barriers?
Innate Immunity
What is the function of prostaglandins in inflammation?
Cause vasodilation and pain
Which enzyme is responsible for stabilizing the formation of MAC by amplifying more C3 cleavage?
Properdin
What role do C3a and C5a play in complement activation?
Trigger mediator release by mast cells
Which of the following is NOT one of the inflammatory mediators mentioned in the text?
Thrombin
What are the 3 main outcomes of complement activation mentioned in the text?
Lysis of target, Opsonisation, Inflammation
What is assumed to be part of the adaptive immune response but is actually a part of cell-mediated (innate) immunity?
Complement activation
What is the role of Bradykinin in the body?
Increases vascular permeability
Which factor is activated following tissue injury and leads to clot formation?
Factor XII
What is the end product of the Fibrinolytic system after removing clots from injured tissue?
Plasmin
Which complement pathway can be triggered by an Opsonin like Antibody or CRP?
Classical pathway
What is the central importance of Complement factor C3 in the complement pathway?
Attaches to pathogens and leads to increased phagocytosis
In the Kinin system, what is the enzyme cascade that activates pre-kallikrein to form kallikrein?
Hageman factor (Factor XII)
What happens after C4b transfers to the surface of the microbe/cell and C2 binds to it in the presence of Mg2+?
C2 is cleaved by C1s and C2b is released
In the Lectin pathway, what is the trigger for initiating the pathway?
MBL binding to bacterial/infected cell wall
What is the role of MASPs in the Lectin pathway?
Acting as MBL-associated serine proteases
What is formed when factor B associates with C3b in the Alternative Pathway?
'C3 convertase'
Which step leads to the formation of 'C4b2a3b' in the classical pathway?
Recruitment and cleavage of C5 to form C5b
How does the Membrane Attack Complex (MAC) contribute to cytolsis?
'PolyC9' attaches to target cells forming pores
What is the main mechanism by which Natural Killer cells kill target cells?
Inducing pore formation in target cell membranes
Which group of cells does NOT recognize antigen peptides presented by MHC molecules?
Natural Killer T cells
Which type of cells are particularly found in the skin and mucosa during innate immune reactions?
Natural Large Killer cells
What is the main role of ILC2 cells in the immune system?
Wound healing
Which cell type is responsible for producing low affinity antibodies mainly against bacterial antigens?
B1 B cells
Which cell type has a range of surface activatory and inhibitory receptors to recognize infected cells without MHC requirement?
Natural Killer T cells
Prostaglandins, Leukotrienes, and Histamine are examples of inflammatory mediators.
True
The Kinin system is one of the enzyme cascades involved in the complement system activation.
False
Cell-mediated innate immunity involves the killing mechanisms of mast cells and eosinophils.
False
Endocytosis is one of the four main types of defensive barriers/mechanisms of innate immunity.
True
Toll-like receptors (TLRs) and Pattern Recognition Receptors (PRRs) play a role in phagocytosis and innate immune cell activation.
True
Chemokines are primarily involved in the formation of blood clots during inflammation.
False
Kinin system activation leads to increased vascular permeability and vasoconstriction.
True
Thrombin acts on fibrinogen to form fibrin and fibrinopeptides.
True
The Fibrinolytic system is triggered by the activation of Factor VIII.
False
Plasmin is a proteolytic enzyme that contributes to inflammation by breaking down kininogen.
False
The Complement system includes three major activation pathways: Mannose binding lectin, C4 C2 Lectin 3, and Classical Alternative.
False
Complement factor C3 amplifies all reactions in the complement pathway by attaching to pathogens and leading to increased phagocytosis.
True
Properdin helps stabilize the formation of MAC by amplifying more C3 cleavage.
True
C3bBb3b is a 'C5 convertase' that attracts C5-C9 to form the MAC.
False
C5a stimulates eosinophils, and C3a triggers mediator release by mast cells.
False
Chemokines are part of the inflammatory mediators involved in the complement system.
False
Cell-mediated immunity (CMI) is always considered part of the adaptive immune response.
False
C2 binds to C4a and is cleaved by C1s to form C2b
False
In the presence of Mg2+, C3 is attracted and binds to C4b2a in the Lectin pathway
False
Cytolysis occurs when C5b678(poly)9 forms the Membrane attack complex
True
The Alternative Pathway involves the spontaneous cleavage of C5 into C3b and C3a
False
Factor D cleaves the complex of factor B and Mg2+ in the Lectin pathway
False
The Membrane Attack Complex (MAC) contributes to cell lysis through apoptosis
False
Innate Lymphoid Cells (ILCs) do not have PRRs and instead rely on TCR for cell recognition.
False
Natural Killer cells primarily recognize infected cells by binding to MHC molecules.
False
Eosinophils release Major Basic Protein and Peroxidase to fight intracellular pathogens.
False
Neutrophils have a higher production of RNI compared to other phagocytes.
True
Gd T cells express Toll-like receptors and are mainly involved in antiviral immunity.
False
B1 cells require T cell help to produce high affinity antibodies.
False
Natural Killer T cells recognize antigen peptides presented by MHC molecules during innate immunity.
False
Innate and adaptive immunity function independently without interaction or cooperation.
False
Large granular lymphocytes mainly secrete TH1-like cytokines involved in immunity to intracellular pathogens.
False
Monocytes/Macrophages are not part of the innate defence mechanisms described in the text.
False
Study Notes
- Innate immunity includes four main types of defensive mechanisms: anatomical, physiological/chemical, phagocytic/endocytic, and inflammatory.
- Inflammatory response involves the release of various mediators such as prostaglandins, leukotrienes, histamine, cytokines, and chemokines.
- Complement system is a group of serum and cell surface proteins that form an enzymatic cascade upon activation.
- Three complement activation pathways are: classical, alternative, and lectin.
- Classical pathway is triggered by the binding of an opsonin (antibody or CRP) to the target antigen/PAMP/DAMP on the cell surface.
- Lectin pathway is triggered by the binding of MBL and other lectins to bacterial/infected cell walls via PAMP/DAMP.
- Alternative pathway is triggered spontaneously by the cleavage of C3 into C3b and C3a, which sticks to the microbial cell surface.
- The activation of the complement system leads to the formation of the membrane attack complex (MAC), which causes target cell lysis, and opsonisation and inflammation.
- Innate immunity includes several cell types, including natural killer cells (NKs), natural killer T cells (NKTs), and innate lymphoid cells (ILCs), which have distinct properties and functions.
- NKs and ILCs have activatory and inhibitory receptors and secrete cytokines, and they are found particularly in the skin and mucosa during innate immune reactions.
- ILCs are divided into three groups based on their functions: ILC1, ILC2, and ILC3, which secrete different types of cytokines and have different roles in immune responses.
- NKT cells have a TCR but recognise CD1 displaying lipid antigens during innate immunity and kill infected targets mainly via apoptosis and secrete cytokines.
- Other cells involved in innate immunity include eosinophils, neutrophils, basophils, mast cells, gd T-cells, and B1 cells, which have distinct properties and functions.
- Eosinophils are granulocytes that release cationic peptides, major basic protein, and peroxidase to kill extracellular pathogens, particularly worms.
- Neutrophils are granulocytes that have primary (azurophilic) and secondary (specific) granules and are the most abundant type of white blood cells in the body.
- gd T-cells are a subtype of T cells that express CD1 and recognise non-MHC restricted antigens and may phagocytose and present antigens to CD4+ T cells.
- B1 cells are a subtype of B cells that express CD5, are the most frequent in the pleural and peritoneal cavity, and produce low affinity antibodies mainly against bacterial antigens without T cell help and are called natural antibodies.
- Innate and adaptive immunity operate as a highly interactive and cooperative system, producing a combined response more effective than either branch could produce by itself.
Test your knowledge on the detailed steps of the complement system activation process, starting from C4a release to the formation of membrane attack complex (MAC). Explore how C4b, C2, C3, and C5 are involved in the cascade of events.
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