BIOL438: Microbiology for Optometry Week 6 Lecture Notes

Set of flashcards to help students prepare for their microbiology exam by testing their knowledge on the complement system, T cell functions, immune responses, and related concepts.

What is the complement system?

A series of over 30 proteins in blood plasma that helps to tag pathogens for phagocytosis and directly kill pathogens.

What is the function of complement pathway C1?

Protease involved in cleaving C2 and C4.

What does the C3 complement protein do when cleaved?

Forms C3a (anaphylatoxin) and C3b (opsonin) and is key for activating C3 convertase.

What activates the lectin pathway of the complement system?

Recognition of bacterial oligosaccharides ending in mannose or fucose.

Which pathway of complement activation is best activated by antibodies?

Classical pathway.

What is C3's role in the complement system?

C3 is a key complement protein that is cleaved into C3a and C3b, initiating the immune response.

How does the alternative pathway initiate?

It is spontaneous and already initiated when a pathogen enters the body.

What is the function of C5 in the complement system?

Cleaved by C3 convertase to form C5a (anaphylatoxin) and C5b (which interacts with C6 and C7).

What is the membrane attack complex (MAC)?

A structure formed by complement components that create pores in the membranes of pathogens.

What is the function of C9 in the complement system?

Binds C8 to form transmembrane pores in pathogen surfaces.

How is the alternative pathway regulated?

Accelerators stabilize C3bBb on pathogen surfaces; brakes destabilize C3 convertase on host cell surfaces.

What is the role of Properdin (factor P)?

Acts as an accelerator stabilizing C3bBb (alternative pathway C3 convertase) on pathogens.

How does Factor H function in the complement system?

It binds to C3b and promotes its cleavage by factor I, leading to the formation of inactive iC3b.

What is decay accelerating factor (DAF)?

A host cell surface regulator that inactivates C3bBb by promoting dissociation of Bb from C3b.

What is the function of iC3b?

Stimulates phagocytosis when bound to complement receptors on macrophages.

What occurs during the formation of the alternative C5 convertase?

C3bBb recruits an additional C3b to form C3b2Bb.

How do C3a and C5a function in the immune response?

They provoke inflammation and act as chemoattractants for phagocytes.

What is the main role of dendritic cells in the immune response?

To present antigens to T cells and activate them.

What is the structure of a T-cell receptor?

Transmembrane proteins made of heterodimers of α and β (or γ and δ) chains.

What are the two types of MHC molecules?

Class I MHC presents peptides from cytosolic proteins; Class II MHC presents peptides from extracellular proteins.

What do Th1 cells primarily do?

Activate macrophages to enhance their ability to kill intracellular pathogens.

What are the functions of CD4 T cells?

Activate other immune cells, including B cells and macrophages.

What is the primary function of CD8 T cells?

To destroy infected or cancerous cells.

What role do memory B and T cells play in the immune response?

They provide a faster and stronger response upon re-exposure to the same antigen.

What is the process of somatic hypermutation?

Refinement of B-cell receptors to increase affinity for antigens.

How are antibodies produced?

B cells differentiate into plasma cells that secrete antibodies.

What is isotype switching?

The process by which a B cell changes the class of antibody it produces.

What do Tregs do in the immune system?

They regulate the immune response and maintain tolerance to self-antigens.

How does the immune system differentiate self from non-self?

Through positive and negative selection in the thymus.

What is anaphylaxis?

A severe allergic reaction that can be life-threatening.

What is the role of interleukin-2 (IL-2) in T cell activation?

IL-2 promotes T cell proliferation and differentiation.

What is the difference between primary and secondary immune responses?

Primary responses are slower and weaker; secondary responses are faster and stronger due to memory cells.

What factors can modulate the immune response?

Cytokines play a crucial role in activating and regulating immune responses.

What are some characteristics of memory T cells?

They remain long-term after infection and respond more quickly upon re-exposure to the same antigen.

What happens during antigen processing for MHC class II molecules?

Extracellular proteins are digested in phagolysosomes and peptides are presented on MHC class II.

What is the immunological synapse?

The interface between a T cell and an antigen-presenting cell during T cell activation.

How is T-cell receptor signaling initiated?

By the binding of the T-cell receptor to MHC-peptide complexes.

What happens after T cell activation?

T cells proliferate and differentiate into effector cells.

What do cytotoxic T cells use to induce apoptosis in target cells?

Perforin and granzymes create pores and trigger apoptosis.

What cytokines do TH2 cells produce that are important for B cell activation?

IL-4 and IL-5.

What are the roles of antibody isotypes?

Different isotypes (IgM, IgG, IgA, IgE) have specific functions in immune defense.

What is the significance of a high-affinity IL-2 receptor?

Activated T cells gain a high-affinity IL-2 receptor to respond effectively to IL-2.

How does MHC polymorphism impact immune response?

It allows for diverse T cell recognition of pathogens, enhancing the immune system's effectiveness.

What is a conjugate pair in immune response?

The interaction between a T cell and an antigen-presenting cell during activation.

What is the difference between central tolerance and peripheral tolerance?

Central tolerance occurs in the thymus; peripheral tolerance occurs outside of the thymus and helps prevent autoimmunity.

What is the role of CD28 in T-cell activation?

Provides the necessary co-stimulatory signal for T cell activation when bound to B7.

What type of adaptive immune response is generated by B cells?

Humoral immune response.

What is the result of ligand-receptor interaction between CD40L and CD40?

Activation of macrophages through enhanced cross-talk and cytokine production.

How do antibodies neutralize pathogens?

By binding to them and blocking their ability to infect cells.

What are the effects of TH17 cells in the immune response?

They recruit neutrophils to fight extracellular bacteria and fungi.

What is the principal mechanism employed by cytotoxic T cells to kill target cells?

Inducing apoptosis through specific granule secretion.

What is the primary role of IL-4 in the immune system?

To promote B cell differentiation and isotype switching.

What is the difference between the adaptive and innate immune systems?

Adaptive immunity is specific and has memory; innate immunity is non-specific and immediate.

What role do CD8 T cells play in immune surveillance?

They monitor and kill cells infected with intracellular pathogens.

What mechanism leads to the generation of T-cell receptor diversity?

Rearrangement of gene segments during T cell development.

How do regulatory T cells (Tregs) prevent autoimmunity?

By inhibiting the activation of self-reactive lymphocytes.

What is the function of cytokine receptors?

To transduce signals for cellular responses upon cytokine binding.

Under what conditions is B7 expression induced on APCs?

During infection, following PAMP recognition.

What are the effector functions of TH1 cells?

Activate macrophages and enhance their pathogen-killing abilities.

What does the term 'affinity maturation' refer to?

The process by which B cells increase the affinity of their antibodies for an antigen.

How does apoptosis differ from necrosis?

Apoptosis is a programmed, controlled destruction of cells; necrosis is uncontrolled cell death often caused by injury.

What immune cells are responsible for anti-tumor responses?

Cytotoxic T cells and certain subsets of helper T cells.

What is the function of memory B cells?

To provide a quicker and more robust response upon re-exposure to the same antigen.

How is interferon (IFN-γ) involved in T cell and macrophage interactions?

It enhances macrophage activity and promotes a Th1 response.

What is the role of THF (follicular helper T) cells?

Help B cells in germinal centers to produce high-affinity antibodies.

What is the purpose of antibody class switching?

To enable B cells to produce different classes of antibodies with varying functions.

What property of antibodies allows them to neutralize pathogens?

Their ability to bind specifically to antigens on pathogen surfaces.

What kind of immune response do CD4+ T cells primarily mediate?

Helper T cell responses which can activate other immune cells like B cells and cytotoxic T cells.

What is the main outcome of clonal expansion in T cell populations?

Increased numbers of specific T cells that can respond more effectively to an antigen.

How does the immune system remember an infection?

Through the generation of memory T and B cells that persist after the infection.

What is recognized by T cell receptors during activation?

Peptides presented on MHC molecules of antigen-presenting cells.

How does T cell signaling initiate transcriptional changes needed for activation?

Through the phosphorylation of signaling molecules following receptor engagement.

What are the consequences of T cell anergy?

Non-responsiveness to antigens that may lead to self-reactivity and autoimmunity.

What is the role of IL-17 produced by TH17 cells?

To recruit and activate neutrophils at infection sites.

What are the three main CD4 T cell types?

TH1, TH2, and TH17 cells, each with distinct functions.

What triggers degranulation of mast cells?

Binding of IgE antibodies to their specific antigens.

What role does the spleen play in the immune system?

Filters blood and is a site for immune responses to blood-borne pathogens.

What do antimicrobial peptides do?

They disrupt the membranes of bacteria and other pathogens.

What is the significance of the germinal center reaction?

It is where B cells proliferate and undergo affinity maturation and isotype switching.

How do dendritic cells contribute to T cell activation?

By presenting processed antigen on MHC molecules in secondary lymphoid tissues.

What processes occur in the thymus during T cell development?

Positive and negative selection to ensure functional and non-self-reactive T cells.

What is the role of the chemokine CCL21 in T cell migration?

It guides T cells to secondary lymphoid tissues.

How does desensitization work in allergen exposure?

Repeated exposure to allergens can lead to a decreased immune response.

What characterizes an autoimmune disease?

Immune responses mistakenly targeting the body’s own cells.

What is cytokine storm?

An overproduction of cytokines that can result in severe systemic inflammation.

How do activated B cells function after exposure to their specific antigen?

They replicate and differentiate into plasma cells that secrete antibodies.

What is the general role of interferons (IFNs) in the immune response?

They enhance the capabilities of immune cells and inhibit viral replication.

How do TLRs (Toll-Like Receptors) affect T cell responses?

They recognize pathogen-associated molecular patterns, initiating T cell activation.

What function does CD40L serve in T cell interactions?

It binds to CD40 on B cells and macrophages, aiding in their activation.

How can pathogens evade the immune response?

By altering their surface antigens or suppressing immune signaling pathways.

What is the function of natural killer (NK) T cells?

They act in a manner similar to both adaptive and innate immune cells against tumors and infections.

Which cytokines are key in forming a TH2 response?

IL-4 and IL-5.

What type of immunity do antibodies provide?

Humoral immunity, which involves the secretion of antibodies to neutralize pathogens.

What is the significance of the lymphatic system in immune responses?

It transports lymphocytes and other immune cells throughout the body.

What is the primary role of cytotoxic T lymphocytes (CTLs)?

To detect and kill infected cells.

What ligands signal inflammation to immune cells?

Cytokines and chemokines released from infected tissues.

What initiates the complement cascade?

Pathogen recognition by antibodies or complement proteins.

How do vaccines work in relation to memory immune responses?

They expose the immune system to an antigen to create memory cells for faster future responses.

What are the cellular products of a CD8 T cell upon activation?

Effector CTLs that can kill infected cells.

What contributes to tissue rejection in organ transplants?

Recognition of foreign MHC molecules by the recipient's immune system.