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Immunology Test 1 with Complete Solutions
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Immunology Test 1 with Complete Solutions
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Immunology Test 1 with CompleteSolutions
The ability of the immune system to not attack self antigens and nonharmful
environmental antigens is called: - correct Answer-Immune Tolerance
Food antigens, because they lack PAMPs (not carrying the ball) will not stimulate
immune responses.
Mutation of a surface antigen of a microbe is most likely to interfere with which aspect of
host defense? - correct Answer-3rd line: Adaptive immunity
Four types of receptor-ligand interactions are important for immune system function: -
correct Answer-• PAMPs and PRRs
• MHC and antigen presentation
• Antigen receptors
• Cytokine receptors
PRRs - correct Answer-Pattern recognition receptors
Receptors on immune cells bind to ligands (PAMPs) and become stimulated
Type of PRR: Toll-like receptors (TLRs) bind different classes of PAMPs
LRR domian (ligand binding): Extracellular
Transmembrane
TIR domain (signaling): Intracellular
TLR 4 binds to Bacteria LPS
TLR 3/3: Endosomal TLR for viruses- Activates a different transcription factor through
phosphorylation (Interferon pathway, instead of. inflammatory cytokines)
Additional PRRs include the NOD-like receptors (NLRs), which are cytosolic receptors
that recognize ligands from microbes (e.g. bacterial peptidoglycan), host (e.g. ATP) and
environment (e.g. alum). NLRs are involved in signal transduction (like TLRs) but also
play a role in inflammasome formation. When activated, the inflammasome induces the
formation of IL-1 and IL-18, two inflammatory cytokines.
What are PAMPs and what is their role in host immune responses? Include a specific
example in your response. - correct Answer-Pathogen (some sore of microbe)
Associated
Molecular
Pattern
They bind to receptors called PRRs
,they stimulate the second line of defense (innate cellular immunity)
For instance, Lipopolysaccharide (LPS) is a PAMP that binds to.........
MHC and antigen presentation - correct Answer-Specialized immune cells, known as
professional antigen-presenting cells (pAPCs), bridge innate and adaptive immune
responses. Dendritic cells and macrophages are innate immune cells that phagocytose
and process microbial antigens (typically, proteins are digested into peptides). They
present these antigen fragments to T lymphocytes, which are adaptive immune cells. A
T lymphocyte uses an antigen receptor (T-cell receptor) to recognize the presented
antigen. Upon binding of the antigen, a signal transduction cascade stimulates T
lymphocyte activation and subsequent adaptive immune responses.
pAPCs use membrane proteins called major histocompatibility complex (MHC) proteins
to display the processed antigen on the cell surface, so that the antigen-MHC complex
is recognized by the T-cell receptor (TCR).
Two types of MHC are expressed
-MHC I is comprised of two polypeptide chains - α chain and β2-microglobulin. MHC II is
comprised of two polypeptide chains - α chain and β chain (try not to confuse these
chains with those of TCR, described later).
Each MHC molecule has a general peptide-loading domain. Peptide binding to MHC
does not have the specificity of antigen receptors. The APC uses MHC to present a
peptide antigen to T cell by interacting with the T-cell receptor and a co-receptor
MHC I also has a recognition domain for the CD8 co- receptor on T cells. So, if a pAPC
is infected with a virus, it will present these antigens with MHC I to a CD8 T cell. This
activates cytotoxic T cells that target virus-infected host cells.
MHC II also is recognized by the CD4 co-receptor on T cells. So, if a pAPC
phagocytoses a bacterial cell, it will present these antigens with MHC II to a CD4 T cell.
This activates helper T cells that coordinate the activities of macrophages to
phagocytose bacteria. In this fashion, the pAPC he
Linking innate and adaptive immune responses - correct Answer-Antigen presenting cell
(APC)
MHC + antigen (Combine piece of microbe/antigen with MHC, then display on surface-
way of presenting antigens to adaptive immune cells to get them activated)
T Lymphocytes (CD4 or CD8)
-T-cell receptor (TCR)
-CD3
-T-cells need antigen to be presented to them
-Produces chemical signals to further activate B-cell
-B-Cell receptor
, -IG alpha and IG beta
-Antigens can just be floating around, doesn't;t need to be presented
-Third line of defense
-Turns into plasma cell, releases antibodies to tag antigens
*Antigen is a ligand
B-cell receptor - correct Answer-B cells express B-cell receptors (BCR) that are
comprised of four polypeptide chains of two different types - heavy chain and light
chain.
Each B cell has a single antigen-binding specificity, i.e. its BCRs recognize one antigen
only. BCR has two antigen-binding sites, each comprised of a heavy chain and a light
chain. The antigen-binding site interacts with an epitope
of a native antigen (e.g. viral spike protein or bacterial toxin). The two heavy chains are
anchored in the cytoplasmic membrane and stabilized by two proteins, called Igα and
Igβ. These two membrane proteins have large cytoplasmic domains with ITAMs
involved in intracellular signaling when antigen binds the BCR.
B cell- antigen binds to b -cell receptor
B cell activation leads to antibody synthesis
Eventually we get cell that produces antibodies
Interleukins (IL) - correct Answer-One group of cytokines, called interleukins (IL), are
used by leukocytes to communicate with one another. For example, when a dendritic
cell presents an antigen to a CD4 T cell, it will secrete interleukin-12 (IL-12).
All the following molecules are involved in activation of the helper T cell response by
antigen presentation except:
A. B cell receptor
B. T cell receptor
C. MHC II
D. CD4 co-receptor
E. Exogenous antigen - correct Answer-B cell receptor
Which statement about bacterial lipopolysaccharide (LPS) is true? (choose all correct
answers)
LPS is an antigen
B
LPS is a PRR
C
LPS is a PAMP
D
LPS is a TLR
E
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