Immunology Lesson 4 Quiz

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Questions and Answers

What initiates the alternative pathway of the complement system?

Hydrolysis of C3 in liquid phase (correct)

Stabilization of C5 component

Binding of C3 to microbial surfaces

Activation by Factor D

What happens to C3b when there is no infection present?

It dismutes into an inactive component (correct)

It forms a C5 convertase complex

It gets stabilized and binds Factor B

It binds to microbial surfaces

Which factor is cleaved by Factor D in the alternative pathway?

Factor B (correct)

Which component prolongs the life of the C3bBb convertase in the alternative pathway?

Properdin Signup and view all the answers

What is the primary role of the Bb fragment in the alternative pathway?

To stabilize C3b Signup and view all the answers

In the context of the alternative pathway, how is Factor D characterized?

As an agent compared to C2 Signup and view all the answers

What happens to the C3bBb complex after it forms the C5 convertase?

It has a short-lived activity Signup and view all the answers

Which component is described as made by neutrophils and stored in secondary granules?

Properdin Signup and view all the answers

What is the primary role of C1q in the classical pathway of the complement cascade?

To bind antibodies and activate proteolytic enzymes Signup and view all the answers

Which two antibodies need to bind to C1q for its activation to occur in the classical pathway?

One antibody to each of the two glomerular heads Signup and view all the answers

What does the C3 convertase (C4b2a) specifically act on in the complement cascade?

It cleaves C3 into C3a and C3b Signup and view all the answers

How does the cleavage of C4 contribute to the complement cascade?

It generates C4b, which covalently binds to the target membrane Signup and view all the answers

What is the consequence of aspecific binding of antibodies to C1q?

It leads to rapid detachment and no activation Signup and view all the answers

Which component is NOT part of the initial cleavage in the complement cascade as initiated by C1q?

C3 Signup and view all the answers

What characteristic structure does C1q possess that is crucial for its function?

Six glomerular heads Signup and view all the answers

What is the main outcome of the complement cascade on the pathogen?

Osmolarity lysis through pore formation Signup and view all the answers

What role does C3b play in the removal of immunocomplexes?

It binds to antibodies and is recognized by C1 receptors. Signup and view all the answers

Which condition results from the absence of C1 inhibitor (C1 INH)?

Hereditary angioedema. Signup and view all the answers

What is the primary function of the C1 inhibitor (C1 INH)?

It inhibits the activation of C1. Signup and view all the answers

How do immunocomplexes pose a risk in the complement system?

They can cause auto-destruction through excessive complement activation. Signup and view all the answers

Which receptor acts as a co-receptor for B-Cells and binds to C3b?

CD21. Signup and view all the answers

What type of molecules do some receptors function as to aid leukocyte activity?

Adhesion molecules. Signup and view all the answers

What is the implication of an increase in C2a concentration in serum?

Increased frequency of endothelial lysis. Signup and view all the answers

Which component of the complement system mimics C4 to inhibit C1 activation?

C1 INH. Signup and view all the answers

What is the primary function of C5b in the complement system?

To initiate the formation of the Membrane Attack Complex (MAC) Signup and view all the answers

Which subclass of immunoglobulin is noted for its high potency in activating the classic pathway of the complement system?

IgM Signup and view all the answers

What happens when Mannose Binding Protein (MBP) interacts with microbial sugars?

It activates MASP, leading to cleavage of C4 and C2 Signup and view all the answers

What is a defining characteristic of Ficolins compared to Mannose Binding Protein (MBP)?

Ficolins recognize different microbial sugars than MBP Signup and view all the answers

What is the role of the C4b2a complex in the complement pathway?

To act as the C3 convertase of the lectinic pathway Signup and view all the answers

How many monomers make up the Mannose Binding Protein (MBP)?

3 Signup and view all the answers

Which of the following components generates over 1000 C3b molecules through a single C3 convertase?

C3 Signup and view all the answers

What structural feature distinguishes Ficolins from other complement-activating proteins?

Fibrinogen-like head Signup and view all the answers

What is the main role of MHC class I and class II molecules?

They present antigens to T cells. Signup and view all the answers

Which characteristic is NOT true about the MHC molecules?

They are exclusively found in humans. Signup and view all the answers

What distinguishes non-classical MHC molecules from classical ones?

Non-classical MHC molecules do not participate in antigen presentation. Signup and view all the answers

What does the term 'polymorphic' refer to in the context of MHC genes?

It refers to the presence of multiple alleles for a single gene in a population. Signup and view all the answers

In terms of inheritance, how are MHC genes expressed?

Both maternal and paternal genes are co-dominantly expressed. Signup and view all the answers

Which of the following is NOT a class of MHC molecules?

Class IV Signup and view all the answers

Which statement about MHC molecules is incorrect?

MHC class III molecules are primarily responsible for presenting internal cellular data. Signup and view all the answers

What type of mutation can contribute to the polymorphism seen in MHC genes?

Single Nucleotide Polymorphism (SNP) Signup and view all the answers

What is a characteristic feature of the molecules that are part of the non-classical HLA class I group?

They are coded by genes outside the HLA complex. Signup and view all the answers

Which role do ULBP molecules primarily play in the immune response?

They activate NK cells. Signup and view all the answers

What distinguishes the C1 complex from classical HLA class I molecules?

C1 molecules show glycolipids instead of proteins in their pocket. Signup and view all the answers

How does the neonatal Fc receptor (FCRN) function in the immune system?

It transports immunoglobulins from mother to fetus. Signup and view all the answers

Which cells express ULBP proteins that can be recognized by NK cells?

MK and MB cells induced by cytomegalovirus infection. Signup and view all the answers

What structure characterizes HLA class II molecules?

Heterodimer made of two chains and a transmembrane domain. Signup and view all the answers

In what way do non-classical HLA molecules influence T cell activity?

They activate only alpha-beta T cells. Signup and view all the answers

What is the primary role of the ZAG protein in relation to the immune response?

It is involved in lipid homeostasis and less related to immune response. Signup and view all the answers

Study Notes

Lesson 4 - Immunology

Ligands activate TRADD or FADD domains, which are dead domains in FAS and TNF receptor families.
Molecules bind to cytosolic tails of receptors, activating caspases.

Summary of Receptors

Homodimer Receptors: G-CSF is the only homodimer receptor.
β Common Chain: The β chain is the same across all receptors. The α chain is specific.
γ Common Chain: The γ chain is identical across receptors; α and β chains vary. This chain is common for many Interleukins (ILs), allowing different functions.
Specific Receptor Examples: G-CSF, IL-3, IL-5, IL-2, IL-4, IL-6, LIF, GM-CSF, IL-7, IL-9, IL-15, LIF and IL-6 receptors (heterodimers). The specific chain of the receptor recognizes and binds the cytokine, while the transduction chain is called gp130.
γ-Chain Mutation: Mutations or absence of the γ chain can lead to severe combined immunodeficiencies.

IL2 Receptors

Resting Lymphocytes: Require a higher concentration of IL-2 to bind the receptor initially (lower affinity).
Activated Lymphocytes: Produce the α chain, increasing IL-2 affinity, requiring less IL-2. This creates a competitive advantage inside lymphoid tissue.
IL-2 Functions: Activation and proliferation of T, B, and NK cells; maturation and activation of Th2, B cells, and mast cells.

Cytokine Receptor Functions

Several functions depending on the receptor. Some ligands induce calcium release and MAPK pathway activation.
Cytokines can induce SOCS (suppressor of cytokine signaling), which can stop JAK activation, ubiquitinate/degrade STATs, or stop cytokine expression.

Chemokines

A family of small cytokines characterized by chemotaxis (movement in response to chemical stimuli), directing immune cell recruitment to sites of infection.
There are 4 families (alpha, beta, 2 other families with one member each).

Complement System

The complement system was first identified by Bordet early in the 20th century, identifying the serum's ability to kill bacteria.
It involves 30+ blood proteins in a cascade sequence, triggered by different pathways:
- Classical Pathway: Activated by changes in IgM and IgG antibodies.
- Lectin Pathway: Activated by microbial sugars, like mannose.
- Alternative Pathway: A spontaneous pathway triggered by microbial surfaces.
Complement proteins are sequentially activated by cleavage/activation of the next inactive protease in a cascade. Products of complement activation promote inflammation and pathogen destruction via lysis.
Regulation: Proteins control the pathways to prevent uncontrolled activation.
Functional Meaning: Cell killing, opsonization, inflammation, and removal of immune complexes.

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Description

Test your understanding of key concepts in immunology with this quiz focused on receptor mechanisms and the roles of ligands. Explore details such as homodimer receptors and IL2 receptors as well as the effects of chain mutations on immune functions.