BSCI437 Exam III - adaptive immune response

adaptive immune system

A specialized part of the immune system that adapts its response to specific pathogens, providing long-lasting immunity through the activation of lymphocytes and the production of antibodies.

• specific

• memory

specific

trait of adaptive immune system

• protection is directed against specific molecules

memory

trait of adaptive immune system

• after initial exposure to foreign antigen, the body reacts more vigorouslyt and quickly at the next encounter with the same antigen

humoral

adaptive immune system branch

• antibody mediated

• defense provided by B cells

  • produce antibodies

• targets extracellular pathogens (free viruses)

  • in blood stream and mucosal surfaces

  • can target cells with foreign surface proteins

cell mediated

adaptive immune system branch

• defense provided by T cells

  • target intracellular pathogens (infected cells)

  • ex. cancel cells, infected cells, transplants

adaptive immune system cells

lymphocytes

• B calls

• T cells

lymphocytes

• migratory cells that circulate in the blood and lymphatic system; settle in organs

  • B and T cells

CD4

Helper T Cells

CD8

killer T cells (cytotoxic)

antibodies

proteins produced by B cells that bind to specific antigens, aiding in their neutralization or destruction

• 2 functional ends

  • Fab

  • Fc

Fab region

region of antibodies

• recognize specific epitopes

• heavy and light chains

Fc

region of antibodies

• region that acts as ligands for Fc receptors on phagolytic cells (macrophage, neutrophil, etc.)

opsonizaiton

• immune process where particles like bacteria are targeted for destruction by an immune cell known as a phagocyte

  • identifying the invading particle to the phagocyte by marking it with opsonins, such as antibodies.

opsonin

any molecule that marks pathogens for phagocytosis; binding enhancer for process of phagocytosis

• ex. complement components, antibodies

IgG

main antibody of secondary responses

• neutralizes toxins

• opsonization

antibody functions

• often

  • fix complement

  • phagocytosis

• cytotoxic clearing

• aggregate virus

• neutralize binding/uncoating

fix complement

function of antibody

• complement factors poke holes/viruses and opsonize viruses marking them for phagocytosis

• interacts with all arms of the immune system

phagocytosis

antibody function

• in which immune cells engulf and digest pathogens or debris, enhancing immune response

phagocytic receptors

molecules on immune cells that recognize and bind to pathogens or antibody-coated surfaces, facilitating their engulfment.

• receptors for opsonins

• PRRs

• receptors for apoptotic cells

receptors for opsonins

molecules that bind to antibodies or complement proteins on pathogens, enhancing their recognition and uptake by phagocytic cells

ex. complement receptors, Fc receptors

pattern recognition receptors (PRR)

molecules on immune cells that detect patterns associated with pathogens, playing a crucial role in initiating immune responses.

ex. mannose receptor

receptors for apoptopic cells

molecules that recognize and bind to cells undergoing programmed cell death, facilitating their clearance by phagocytes

ex. TREM receptors, scavenger receptors

cytotoxic clearning

antibody function

• antibody dependent cell mediated cytotoxicity

• mechanism of cell mediated immune defense

  • effector cell of the immune system actively lyses target cell whose membrane surface antigens have been bound by specific antibodies

ex. envelope virus

envelop virus

virus that puts viral proteins on the cell membrane for budding

virus aggregation

antibody function

• binding and clustering of viruses, enhancing opsonization and subsequent clearance by immune cells

neutralize binding/uncoating

antibody function

• can directly block interferons of pathogens (neutralize Ab/tissue culture cells)

• Non neutralizing Abs cannot directly block an infection

  • they trigger opsonization and complement and other pathways

• Abs made of a pathogen may be of either type

• Has to do with what specific antigen they recognize and what protein they bind does to the virus life cycle

bone marrow

where precursors of the cellular immune response cells are produced

thymus

where naive T cells are matured

T cells

specialized white blood cells

• recognize short linear peptides

  • recedtor recognizes signle things

antigen presenting cells (APC)

cells that display antigens on their surface for T cell recognition. They play a crucial role in initiating the adaptive immune response

• nairve T cells are archived by ___

memory T cells

a subtype of T cells (can be either CD8 or CD4)

• generated if alr exposed to pathogen

• primed and ready to proliferate if previous same antigen shows itself again

T cell receptor (TCR)

a molecule on the surface of T cells that specifically recognizes and binds to antigens presented by Major Histocompatibility Complex (MHC) molecules, enabling T cell activation

• Heterodimeric membrane associated

• Recognize linear peptide derived from proteolytic processing

Interaction between receptors and a ligand are highly specific

MHC I

molecules present antigens to CD8+ T cells

• all cells have this MHC

• cytotoxic T cells can recognize the peptide and kill infected cell

MHC II

molecules present antigens to CD4+ T cells

• Helper T cell

• Interact with B cell and antigen presenting cells (MHCII)

T cell response specificity

HIGHLY SPECIFIC ensures that the immune system does not kill non infected cells

• Two levels

  • Peptider must associate with given MHC molecule

    • Ends of the peptide are buried within the closed ends of class I binding groove

    • center bulges out for presentation to the TCR

  • Mature T cells must have a T cell receptor that recognizes the peptide associated with MHC

costimulatory molecules

are proteins required for T cell activation that work alongside antigen recognition

• checks that make sure T cells are not activated by the wrong cell

ex. APC

MHC I processing

method of processing

• through ER and golgi

• Peptides

  • Come from proteasome and may include either self or foreign antigens

self antigens

antigens that do not trigger any response because the T cells that would have responded to them are eliminated during development of immune system

autoimmune disease

a condition where the immune system mistakenly attacks the body's own cells, recognizing them as foreign

• Due to a new antigen being produced in the person or to a T/B cell that is aberrantly activate

MHC II processing

method of processing

• Exogenous

• Expressed on

  • antigen presenting cells that activate T helper cells

  • B cells so they can interact with T helper cells during their activation

through the endosomal/lysosomal pathway, leading to the presentation of extracellular peptides to CD4+ T cells.

cytotoxic T lymphocytes (CTL)

CD8+ T cells

CTL killing

• Kills cells by

  • Pokes them with perforin

  • then dumping in enzyme that activates

    • Apoptosis

    • Other degrading pathways

CTL activation

Normally present in naive forms

• When CTL interact with APC that presents antigen that Naive T cell recognizes, they become activated

• Activated form carries immune response

Naive T helper cells

Recognizes antigen bound to MHC II on APC\

Naive CTLs

recognize antigen bound to MHC on APC

memory cells properties

Properties

• Survive for years in body

• Ready to respond

• Upon encountering antigen, rapidly proliferate

• Efficient production of defensive products

Antibody dependent enhancement (ADE)

Instead of neutralizing a virus, sub-neutralizing antibodies bind to it and actually facilitate its entry into immune cells 

ex. Dengue hemorrhagic fever or shock syndrome

Dengue hemorrhagic fever

• Non neutralizing Abs made against virus bins the virus and targets it for phagocytosis by macrophage

  • Leads to macrophage to becoming infected by virus

• Dengue virus does not infect macrophages, but Ab allows them to get in and cause infection

• Common with secondary infection

  • Titer of Ab is higher

  • When straight of dengue is different thana primary infection

    • Abs made to the primary infection are less likely able to neutralize secondary infection by another strain

Indirect effect

infection interferes with synthesis of critical molecule need for hosts to survive

Immunopathology

damage caused by immune system

• CTL

• CD4 T cells

• B cells

• Innate immune system