MICR 270 TESTED QUESTIONS WITH ANSWERS REVISED & UPDATED!!
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MICR 270
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MICR 270
MICR 270 TESTED QUESTIONS WITH ANSWERS REVISED & UPDATED!!
Steps of innate TLR recognition - Answer-1) TLRs recognize PAMPs/DAMPs and initiate phagocytosis
2) Phagocyte presents pathogen on its cell surface through a complex called peptide:MHC complex (phagocyte is now an antigen-presenting cell)...
MICR 270 TESTED QUESTIONS
WITH ANSWERS REVISED &
UPDATED!!
Steps of innate TLR recognition - Answer-1) TLRs recognize PAMPs/DAMPs and
initiate phagocytosis
2) Phagocyte presents pathogen on its cell surface through a complex called
peptide:MHC complex (phagocyte is now an antigen-presenting cell)
3) Phagocyte stimulates production of costimulatory molecules, which increase strength
of antigen-presenting process
4) T-cell binds to the peptide:MHC complex, which activates the T-cell
Inflammation - Answer-innate process that aims to localize and eliminate an invading
pathogen by adding heat (increasing metabolic rates of immune cells) and swelling
(leaks clotting proteins to form scabs, recruits lymphocytes)
Steps of inflammation - Answer-1) Breach: pathogen enters through a wound or body
opening
2) Vasodilation: induced by vasoactive and chemotactic factors secreted by immune
cells and damaged tissues to increase heat
3) Permeabilization: excess fluid at the site of infection (exudate) contains pro-
inflammatory cytokines called chemokins and complement, eventually forms edema
4) Extravasation: chemotactic factors induce immune cell recruitment - neutrophils are
the first to arrive by chemotaxis, where they adhere to endothelial cell walls via
margination and migrate to infected tissue via diapedesis
Phagocytosis - Answer-innate process where phagocytic cells (neutrophils,
macrophages, and dendritic cells) take up particulate material by invaginating their
membranes to form a vacuole - induced by PRR PAMP recognition and pathogen
opsonization
Steps of phagocytosis - Answer-1) Attachment: pathogen is attached to membrane
evaginations (pseudopodia)
2) Ingestion: pseudopodia surround pathogen, forming a vacuole called a phagosome
3) Fusion: phagosome fuses with a lysosome, which releases enzymes
4) Digestion: pathogen is destroyed and digested by lysosomal enzymes
5) Release: digestion products are released from the cell via exocytosis
Process of antigen recognition - Answer-1) Antigen presenting cells phagocytose
pathogens
,2) Pathogens are processed to form a peptide:MHC complex
3) B and T cells interact with APCs to recognize an antigen
Types of APCs - Answer-- Professional APCs: most efficient cells that present antigens
through MHC class II complexes as well as expressing costimulatory signals to activate
helper T cells (Dendritic cells (most effective), macrophages)
- Nonprofessional APCs: usually don't express MHC class II complexes, but can be
induced to do so (Fibroblasts, glial cells)
Pathways of MHC complex processing - Answer-- Endogenous pathway: forms
peptide:MHC class I complexes which are recognized by CD8 T-cells
- Exogenous pathway: forms peptide:MHC class II complex which are recognized by
CD4 T-cells
B and T cell receptors (APC recognition) - Answer-- B-cell receptor: composed of
membrane-bound antibodies and signal transduction molecules (ITAMs) which bind to
extracellular pathogens directly
- T-cell receptor: consist of antigen-specific molecule (CD3) and signal transduction
molecules (ITAMs) which bind to peptide:MHC complexes
B-cell activation - Answer-a) Antigen binds to a receptor on the B-cell
b) Antigen is internalized by receptor-mediated endocytosis
c) B-cell displays antigen on its cell membrane as a peptide:MHC class II complex (B-
cell is acting as an APC)
d) CD4 TH2 cell recognizes and binds to the complex
e) The binding of the complex induces the expression of costimulatory molecules
CD40L and CD28 on the T cell and CD40 and B7 on the B-cell
f) CD40L-CD40 and CD28-B7 bind together
g) The T-cell secretes cytokines, which binds to their associated receptor on both cells
(both paracrine and autocrine)
h) B-cells are differentiated into plasmocytes and memory-B cells
T cell activation - Answer-a) CD4 TH1 cells bind to an APC, forming an immune
synapse
Arranged in a pattern with three rings of clusters of cells with similar functions, called
supra molecular activating clusters (SMAC)
- Signal molecules (cSMAC): central ring, contains the molecules responsible for
signalling between the TCR and peptide:MHC molecules
- Adhesion molecules (pSMAC): middle ring, contains adhesion proteins (eg. integrins
and cytoskeletal linker proteins) that keep the cells long enough for signals to propagate
- Signal regulation molecules (dSMAC): outer ring, consists of proteins that help
regulate signal transduction
b) Activate CD8 cells, which initiates cell-mediated immunity
Types of cytokines - Answer-- Chemokines
- Interleukins
Chemokines - Answer-- Induce chemotaxis
- Call cells to a region of infection/injury
- Involved in: inflammation, wound healing, adaptive pathogen elimination,
hematopoiesis
Interleukins - Answer-- Regulate immune responses
- Affect proliferation and differentiation of hematopoietic/immune cells
Interferons - Answer-- Most common types are alpha, beta, and gamma IFNs
- Induce an antiviral state to inhibit viral replication
- Regulate immune responses
Tumor necrosis factor - Answer-- Most common types are alpha and beta TNFs
- Involved in systemic inflammation (septic shock) and tumour regression
- Can cause apoptosis
Cell-mediated immunity (T-cells) - Answer-CD8 cytotoxic cells kill identified cells that
have been infected with viruses
Humoural immunity (B-cells) - Answer-plasmocytes produce antibodies
Types of antibodies - Answer-- surface antibodies: form part of the B-cell receptor on
the membrane)
- soluble antibodies: secreted by plasmocytes and circulate freely in the blood)
Functions of antibodies - Answer-- Neutralize biological effect of pathogen
- Mark pathogen for phagocytosis (opsonization)
- Activate MACs to lyse the pathogen
Structure of antibodies - Answer-- Heterodimeric proteins held together by disulfide
bonds
- Two light chains form the antigen-binding regions
- Two heavy chains form the Fc region (interacts with immune cell receptors)
Classes of antibodies - Answer-IgM, IgG, IgA, IgE, IgD
IgM - Answer-- Forms a pentamer
- First antibody to be formed in an immune response
- Activates the complement, which then amplifies the inflammatory and adaptive
immune response
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