Immunology Study Guide: Chapters 8-11

A collection of flashcards covering key immunological concepts, pathways, and immune cell functions based on the study guide.

What is required for the activation of naive T cells?

Antigen presentation by dendritic cells in secondary lymphoid organs.

What are the three signals required for T cell activation?

1. Antigen Recognition, 2. Co-stimulatory Signal, 3. Cytokine Signaling.

What is the role of CD28 on T cells during activation?

It binds to B7 (CD80/CD86) on APCs to provide a co-stimulatory signal.

What happens to CD8+ T cells after activation?

They become cytotoxic T lymphocytes (CTLs) that kill infected or cancerous cells.

What are the distinct subsets of CD4+ T cells and their functions?

Th1: Activate macrophages; Th2: Promote antibody production; Th17: Enhance neutrophil response; Tfh: Support B cell activation; Treg: Suppress immune responses.

What cytokine do Th1 cells secrete and what is its function?

They secrete IFN-γ, which activates macrophages and enhances intracellular pathogen killing.

What is the function of cytotoxic T lymphocytes (CTLs)?

They kill infected or cancerous cells using the perforin/granzyme pathway or Fas-FasL interaction.

How do CD4+ Th cells enhance macrophage activity?

Through Th1 cells, which promote phagolysosome fusion.

What is somatic hypermutation (SHM)?

Random point mutations in variable regions of B cells to improve antigen affinity.

What is class switching recombination (CSR)?

A process determined by cytokines that switches B cells to produce different antibody isotypes.

What initiates T cell-dependent (TD) B cell activation?

Help from Tfh cells and CD40-CD40L interaction.

What is the predominant antibody produced during T cell-independent (TI) activation?

IgM with limited memory formation.

What is the role of memory B cells?

They are long-lived cells with high-affinity receptors for rapid secondary responses.

What is the role of neutralization by antibodies?

It prevents pathogen binding to host cells, primarily through IgG and IgA.

How do antibodies enhance phagocytosis?

Through opsonization, primarily via Fcγ receptors on IgG.

What immune response involves Type I interferons?

They inhibit viral replication.

What are Th17 cells primarily involved in?

They enhance the neutrophil response to extracellular bacteria and fungi.

What immune mechanism do large parasites require?

Eosinophils, mast cells, and IgE.

What is antigenic variation?

A strategy used by pathogens like influenza and HIV to evade the immune system.

What is the effect of HIV on the immune system?

It targets CD4+ T cells, leading to immune suppression.

What are primary immunodeficiencies?

Congenital deficiencies affecting immune function, such as SCID and X-linked agammaglobulinemia.

What is an example of a secondary immunodeficiency?

HIV/AIDS or malnutrition, which impairs T cell function.

What causes autoimmune diseases?

Loss of self-tolerance due to genetic or environmental factors.

What type of hypersensitivity reaction is mediated by IgE?

Type I hypersensitivity, such as allergies and anaphylaxis.

What are the components and their functions in the immune system?

Dendritic Cells: Antigen presentation; CD4+ T Cells: Help B cells; CD8+ T Cells: Kill infected cells; B Cells: Produce antibodies; Macrophages: Phagocytosis; Neutrophils: First responders; NK Cells: Kill virus-infected cells.

What are the primary pathways of B cell activation?

T cell-dependent and T cell-independent activation.

What do Tfh cells do in the immune response?

Support B cell activation in germinal centers.

What is the effect of IL-4 in antibody production?

It promotes class switching to IgE.

What is the role of complement activation in immunity?

Opsonization, pathogen lysis, and immune complex clearance.

What are the key players in a humoral immune response?

B cells, Tfh cells, and antibodies.

What cytokine would trigger class switching to IgA?

TGF-β.

How do antibodies mediate ADCC?

NK cells recognize and induce apoptosis in antibody-coated cells.

What is the role of CTLA-4 on Treg cells?

Inhibits APC activation by removing B7 molecules.

How does Mycobacterium tuberculosis evade the immune system?

By preventing phagolysosome fusion.

What do Th2 cells drive in relation to parasitic defense?

IgE class switching.

What defines CD8+ T cell activation?

Engagement of TCR with peptide-MHC and costimulation.

What is the purpose of affinity maturation in B cells?

To select B cells with the highest affinity antibodies for survival.

What is the consequence of T cell receptor (TCR) binding to the peptide-MHC complex?

It triggers T cell activation.

What type of immune response is characterized by delayed-type hypersensitivity?

Type IV hypersensitivity, mediated by T cells.

What cytokines do Treg cells secrete to suppress immune responses?

IL-10 and TGF-β.

What role do neutrophils play in infections?

They are the first responders and participate in phagocytosis.

What is the outcome of chronic granulomatous disease (CGD)?

Defective phagocytic killing leading to recurrent infections.

What is the primary function of macrophages in the immune system?

Phagocytosis, antigen presentation, and cytokine release.

What happens during clonal expansion in T cells?

Activated T cells proliferate and differentiate into effector cells.

What cell types are critical for the humoral immune response?

B cells and T helper cells (especially Tfh cells).

What immune response activates CD4+ T cells to assist B cells and macrophages?

Cytokine signaling and antigen recognition.

How do different T cell types aid in the immune response?

Through distinct functions such as cytotoxic activity, helper functions, and regulation.

Which immunodeficiency results in no functional T and B cells?

Severe Combined Immunodeficiency (SCID).

What are the key characteristics of memory B cells?

Long-lived with high affinity for antigens for rapid response upon re-exposure.

What type of antibodies are mainly produced during T cell-independent activation?

IgM.

What is macrophage activation a direct result of?

CD4+ T cell signaling, particularly from Th1 cells.

What is the main difference between primary and secondary immune responses?

Memory cells are present in secondary responses for a faster and stronger reaction.

What are the distinct roles of antibodies in immunity?

Neutralization, opsonization, complement activation, and ADCC.

What defines antigenic drift and who employs it?

Antigenic drift refers to the minor mutations in viruses (like influenza) that help evade immunity.

What immune cells are critical in combating helminth infections?

Eosinophils and mast cells.

What type of immune response is primarily driven by Th17 cells?

Responses against extracellular bacteria and fungi.

What is the consequence of antigen presentation inhibition by herpes simplex virus?

Inhibition of MHC I presentation leading to immune evasion.

What is the ultimate fate of B cells with low-affinity antibodies during affinity maturation?

They are selected against and do not survive.

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

To present antigens to naive T cells.

What is the function of the complement system?

Opsonization and pathogen lysis.

What describe the process through which B cells change antibody isotype?

Class switching recombination based on cytokine signals.

What can result from a chronic immune response against self-antigens?

Autoimmune diseases like Type 1 Diabetes and Multiple Sclerosis.

What type of hypersensitivity involves IgG-mediated destruction of cells?

Type II hypersensitivity.

What do Th1 cells promote within the immune system?

The activation of macrophages to eliminate intracellular pathogens.

What is the role of perforin and granzyme in CTLs?

They are used by CD8+ T cells to induce apoptosis in target cells.

What occurs when a T cell recognizes an antigen without co-stimulation?

It may become anergic or undergo apoptosis.