MICR 270 MODULE 3 - FINAL EXAM QUESTIONS WITH VERIFIED SOLUTIONS LATEST UPDATE 2026
what is the one characteristic that both innate and adaptive immunity have in common? - Answers
self/non-self discrimination
what is the overall immune response? - Answers from the entrance of the pathogen in body to its
elimination
- formed by innate and adaptive immunity and has innate and adaptive IR
- if innate immunity gets overwhelmed, adaptive IR will be developed against infectious agent
what is the adaptive IR? - Answers five phases that occur after the pathogen has evaded innate
immune defences
- antigen recognition (antigen presentation)
- lymphocyte activation
- elimination of pathogens
- apoptosis of immune cells (contraction)
- establishment of immunological memory
1. antigen recognition - Answers - Antigen presenting cells (APCs) like dendritic cells and
macrophages, detect PAMPs
-The APCs will present antigens to naïve T-cells via their surface Major Histocompatibility Complex
(MHC) proteins
2. lymphocyte activation - Answers - process requires series of cellular interactions (communication)
which leads to T cell and B-cell differentiation and clonal expansion
- clonal expansion = production of a large quantity of identical cells from the same original cell
- B-cells = plasmocytes
- T-cells = helper T cells or; cytotoxic T cells
3. elimination of pathogens - Answers - Humoral immunity = plasmocytes produce antibodies that
bind to extracellular pathogens
-Cell-mediated immunity = cytotoxic T cells destroy cells infected by intracellular pathogens or get
activated by antigens presented by APCs
4. contraction/apoptosis of immune cells - Answers - once pathogen is eliminated, vast majority of
activated lymphocytes undergo apoptosis (cell suicide), and IR gradually declines
5. establishment of immunological memory - Answers -Few adaptive immune cells that survive
contraction phase differentiate into memory cells
-When re-exposed to same antigen, these memory cells proliferate quickly to generate an IR
why vaccinate? - Answers to generate immunological memory
why does the adaptive immunity need a process called antigen presentation? - Answers - necessary
to identify which cell(s) should be activated to encounter specific invader during an infection
why do immune cells die after elimination of pathogen? - Answers - No longer needed, if they stayed
alive would consume unnecessary energy that could be better used in body... also risk that these extra
immune cells could cause damage
what are advantages of having memory cells? - Answers they can last for v long time and will respond
much faster and stronger in case of reinfection with the pathogen
what is key player in self and non-self recognition? - Answers major histocompatibility
complex/MHCs
- these serve as self-labels, and helps identify and recognize self from non-self molecules to ensure IS
does not attack host
what is the role of MHC molecules? - Answers - MHCs are molecules that display antigen complex can
be recognized by the TCR and its co-receptors (CD2 or CD8) to initiate an adaptive IR -> leads to
elimination of foreign antigens
what are the two types of classic MHC molecules? - Answers MHC class I complex -> CD8 cytotoxic
cell
MHC class II complex -> CD4 helper T cell
, what are antigen presenting cells (APCs)? - Answers - helper T cells are essential n process to induce
effective adaptive IR
- T cells not able to recognize extracellular pathogens by themselves, they require an intermediate to
present them the antigens -> these intermediates are APCs
what do APCs do? - Answers - APCs internalize pathogens by phagocytosis or receptor mediated
endocytosis and process them into peptides/antigens
- peptides/antigens are then displayed on MHC on surface of APC and can then be recognzed by T
cells
What do APCs express? - Answers MHC class II complex
what are the types of APCs? - Answers 1) Professional APCs
2) non-professional APCs
What are professional APCs? - Answers - macrophages, B cells and dendritic cells
- most efficient cells that both present antigens through MHC class II and express costimulatory
signals to activate helper T cells
what are non-professional APCs? - Answers - some other cell types can be induced to express MHC
class II complexes or stimulatory molecules, but normally they don't
- this is bc these cells will rarely be needed in this specfic function and only for short periods of time in
case of sustained inflammatory responses
what are examples of non-professional APCs? - Answers fibroblasts and glial cells
antigen processing - Answers - each antigen presented by a MHC molecule (class I or class II) needs to
be processed to form an effective peptide: MHC signaling complex
what are the pathways that lead to formation of cell surface complexes? - Answers 1) endogenous
pathways
2) exogenous pathways
endogenous pathways - Answers - forms peptide: MHC class I complex (recognized by CD8 cytotoxic T
cells)
Exogenous pathways - Answers - forms peptide: MHC class II complex (recognized by CD4 helper T
cells) -> lead to humoral immunity and antibody production by plasmocytes
*** vaccination strategies attempt to induce this type of immunity
process of antigen processing by the exogenous pathway? - Answers 1. antigen engulfment
2. proteolytc processing
3. formation of MHC antigen complex
4. cell-surface expression
5. recognition by helper
1. antigen engulfment - Answers APCs like macrophages, B cells or dendritic cells, engulf foreign
antigen by endocytosis -> form endosome
2. proteolytic processing - Answers foreign antigens inside endosome are broken down into
fragments by proteolytc processing = proteases cleave one or more bonds in target protein to modify
its activity (activation, inhibition or destruction of activity)
3. formation of MHC antigen complex - Answers vesicle containing foreign fragments fuse with
vesicles containing MHC molecules (originating from the endoplasmic reticulum via the Golgi),
forming MHC-antigen complexes
4. cell surface expression - Answers MHC antigen complex is transported to the plasma membrane
where it will be displayed on surface of cell
5. recognition by helper - Answers T cell receptor (TCR) on the surface of a helper T cell binds to the
MHC antigen complex on the cell surface of the APC -> initiate adaptive IR
B-cell receptors (BCR) - Answers - BCR is composed of membrane-bound antibody and signal
transduction molecules (ITAMs = immunoreceptor motif is composed of a repeated sequence of four
amino acids in cytoplasmic tails of cell surface proteins)
- BCRs recognize and bind to extracellular pathogens or toxins directly
T cell receptors (TCR) - Answers - TCR complex is formed of a membrane bound antigen specific
molecule and signal transduction molecules (CD3 and ITAMs)
what is the one characteristic that both innate and adaptive immunity have in common? - Answers
self/non-self discrimination
what is the overall immune response? - Answers from the entrance of the pathogen in body to its
elimination
- formed by innate and adaptive immunity and has innate and adaptive IR
- if innate immunity gets overwhelmed, adaptive IR will be developed against infectious agent
what is the adaptive IR? - Answers five phases that occur after the pathogen has evaded innate
immune defences
- antigen recognition (antigen presentation)
- lymphocyte activation
- elimination of pathogens
- apoptosis of immune cells (contraction)
- establishment of immunological memory
1. antigen recognition - Answers - Antigen presenting cells (APCs) like dendritic cells and
macrophages, detect PAMPs
-The APCs will present antigens to naïve T-cells via their surface Major Histocompatibility Complex
(MHC) proteins
2. lymphocyte activation - Answers - process requires series of cellular interactions (communication)
which leads to T cell and B-cell differentiation and clonal expansion
- clonal expansion = production of a large quantity of identical cells from the same original cell
- B-cells = plasmocytes
- T-cells = helper T cells or; cytotoxic T cells
3. elimination of pathogens - Answers - Humoral immunity = plasmocytes produce antibodies that
bind to extracellular pathogens
-Cell-mediated immunity = cytotoxic T cells destroy cells infected by intracellular pathogens or get
activated by antigens presented by APCs
4. contraction/apoptosis of immune cells - Answers - once pathogen is eliminated, vast majority of
activated lymphocytes undergo apoptosis (cell suicide), and IR gradually declines
5. establishment of immunological memory - Answers -Few adaptive immune cells that survive
contraction phase differentiate into memory cells
-When re-exposed to same antigen, these memory cells proliferate quickly to generate an IR
why vaccinate? - Answers to generate immunological memory
why does the adaptive immunity need a process called antigen presentation? - Answers - necessary
to identify which cell(s) should be activated to encounter specific invader during an infection
why do immune cells die after elimination of pathogen? - Answers - No longer needed, if they stayed
alive would consume unnecessary energy that could be better used in body... also risk that these extra
immune cells could cause damage
what are advantages of having memory cells? - Answers they can last for v long time and will respond
much faster and stronger in case of reinfection with the pathogen
what is key player in self and non-self recognition? - Answers major histocompatibility
complex/MHCs
- these serve as self-labels, and helps identify and recognize self from non-self molecules to ensure IS
does not attack host
what is the role of MHC molecules? - Answers - MHCs are molecules that display antigen complex can
be recognized by the TCR and its co-receptors (CD2 or CD8) to initiate an adaptive IR -> leads to
elimination of foreign antigens
what are the two types of classic MHC molecules? - Answers MHC class I complex -> CD8 cytotoxic
cell
MHC class II complex -> CD4 helper T cell
, what are antigen presenting cells (APCs)? - Answers - helper T cells are essential n process to induce
effective adaptive IR
- T cells not able to recognize extracellular pathogens by themselves, they require an intermediate to
present them the antigens -> these intermediates are APCs
what do APCs do? - Answers - APCs internalize pathogens by phagocytosis or receptor mediated
endocytosis and process them into peptides/antigens
- peptides/antigens are then displayed on MHC on surface of APC and can then be recognzed by T
cells
What do APCs express? - Answers MHC class II complex
what are the types of APCs? - Answers 1) Professional APCs
2) non-professional APCs
What are professional APCs? - Answers - macrophages, B cells and dendritic cells
- most efficient cells that both present antigens through MHC class II and express costimulatory
signals to activate helper T cells
what are non-professional APCs? - Answers - some other cell types can be induced to express MHC
class II complexes or stimulatory molecules, but normally they don't
- this is bc these cells will rarely be needed in this specfic function and only for short periods of time in
case of sustained inflammatory responses
what are examples of non-professional APCs? - Answers fibroblasts and glial cells
antigen processing - Answers - each antigen presented by a MHC molecule (class I or class II) needs to
be processed to form an effective peptide: MHC signaling complex
what are the pathways that lead to formation of cell surface complexes? - Answers 1) endogenous
pathways
2) exogenous pathways
endogenous pathways - Answers - forms peptide: MHC class I complex (recognized by CD8 cytotoxic T
cells)
Exogenous pathways - Answers - forms peptide: MHC class II complex (recognized by CD4 helper T
cells) -> lead to humoral immunity and antibody production by plasmocytes
*** vaccination strategies attempt to induce this type of immunity
process of antigen processing by the exogenous pathway? - Answers 1. antigen engulfment
2. proteolytc processing
3. formation of MHC antigen complex
4. cell-surface expression
5. recognition by helper
1. antigen engulfment - Answers APCs like macrophages, B cells or dendritic cells, engulf foreign
antigen by endocytosis -> form endosome
2. proteolytic processing - Answers foreign antigens inside endosome are broken down into
fragments by proteolytc processing = proteases cleave one or more bonds in target protein to modify
its activity (activation, inhibition or destruction of activity)
3. formation of MHC antigen complex - Answers vesicle containing foreign fragments fuse with
vesicles containing MHC molecules (originating from the endoplasmic reticulum via the Golgi),
forming MHC-antigen complexes
4. cell surface expression - Answers MHC antigen complex is transported to the plasma membrane
where it will be displayed on surface of cell
5. recognition by helper - Answers T cell receptor (TCR) on the surface of a helper T cell binds to the
MHC antigen complex on the cell surface of the APC -> initiate adaptive IR
B-cell receptors (BCR) - Answers - BCR is composed of membrane-bound antibody and signal
transduction molecules (ITAMs = immunoreceptor motif is composed of a repeated sequence of four
amino acids in cytoplasmic tails of cell surface proteins)
- BCRs recognize and bind to extracellular pathogens or toxins directly
T cell receptors (TCR) - Answers - TCR complex is formed of a membrane bound antigen specific
molecule and signal transduction molecules (CD3 and ITAMs)
