13: Adaptive Defenses Flashcards
What is adaptive immunity?
Adaptive immunity Is tailored to viruses
What is the overview of adaptive immunity?
- B lymphocyte (B cells)
-> plasma cells- specific antibodies [immunoglobulin Ig]
- antibodies bind to viral [antigens Ag]
- T lymphocyte (T cells)
-> T helper cells- Th cells
- CD4+ T cells
-> Cytotoxic T cells - CTL
- CD8+ cells
What is the bridging process between innate and adaptive immunity?
- Viruses bind to epithelial cells, cells produce cytokines.
- Uptake of viral proteins. Cytokines release and toll-like receptors on immature dendritic cells are activated, viral proteins are taken up by dendritic cells from dead cells
- Recognition of viral proteins by B and T cells: Dendritic cells mature, process viral proteins and present peptides on MHC class 2 cell surface receptors. Information exchange between dendritic cells and naive T cells occurs in lymphatics.
- B and T cells are activated by viral infections that stimulate Th1 response. CTLs, antibody and macrophages clear infection. Memory T cells are established.
What is a pathogen?
It is a microbe, such as viruses, that can cause disease
What is an antigen?
They are a part of a pathogen that can induce a host immune response. “Antibody Generating”
ex. spike protein
What is an epitope?
An epitope is a portion of the antigen that can recognize antibodies.
ex. measles virus has hemagglutinin protein with multiple epitopes
How do antigens (Ag) process and present?
Ag processing is done by degrading pathogens by leukocytes (eg. macrophages) into small peptides.
- Ag peptides are present on the surface with a molecule called Major Histocompatibility Complex (MHC).
Presented:
- Ag on MHC is presented to T cells where Ag binds T cell receptor (TCR)
- Antigen Presenting Cells APC , macrophages, dendritic cells and B cells
Viral Ag processing and presenting in dendritic cells?
There are three pathways for viral Ag presentation depending on the
* Type of Ag (exogenous/endogenous)
* Type of MHC molecules
* Type of T cells (CD4 or CD8)
- MHC 2 pathway
-exogenous Ag to CD4 T cells - MHC 1 pathway
-endogenous Ag to CD8 T cells - Cross presentation
-exogenous then endogenous ; AG to MHC class 1
Ag presentation activates T cells to fight viral infection
How are B cells activated by T Follicular helper cells?
B cells recognize the viral Ag by their receptors (BCR) , engulf it, process it and present it to TFH.
TFH activate the B cells which proliferate and differentiate into plasma cells and memory B cells.
Plasma produces antibodies against the viral Ag.
What are the types of adaptive immune responses?
1) Humoral response:
B cells bind with BRC to viral antigen. B cells differentiate into plasma cells.
2) Cell-mediated response:
T cells are activated by binding to TCL to viral peptides bound by MHC on dendritic cels which create effector T cells
– E TH cells produce cytokine that activate B cells that differentiate into antibody producing plasma cells and activate CTL to kill virus-infected cells
What are Cytotoxic T cells (CTL)?
- The effector CTL recognize viral peptide presented on MHC 1 of infected cells and activate CTL.
- These cells release perforin and granzymes that induce apoptosis
- CTL is activated by IFN release from other cells
What are the classes/isotypes of Ab?
IgA: dimer, surface antibody (mucus & gastro)
IgG: most abundant, blood tissues and circulation.
IgM: pentamer, biggest antibody, lowest affinity
HOW ANTIBODIES NEUTRALIZE VIRUS PARTICLES?
1) Blocked attachment:
Binding of antibody to virus-receptor which blocks virus-receptor binding
2) Blocked endocytosis:
Antibody binds to viral capsid which alters the capsid structure, affects the process of endocytosis
3) Blocked uncoating:
antibodies bind to the virus and fix the capsid in a stable confirmation so the pH doesn’t change and it doesn’t uncoated
4) Neutralization after replication:
Antibodies can be taken up by endocytosis and interact with visions in the cell
5) Aggregation:
Antibodies can aggregate virus particles and facilitate their destruction by phagocytosis
Plasma and monoclonal antibodies for COVID-19 treatment or prevention?
Eteseviamb injection or Bamlanvimab injection
Serum is the liquid that remains after blood is clotted
Plasma is the liquid that remains when cells are removed and clotting
What are the types of adaptive immune response?
- Primary immune response: When B cells are introduced to the Ag for the first time (slow/low magnitude)
- Secondary immune response: When there is a secondary exposure of memory B cells to the set Ag; vaccine development
