MICB 212 MIDTERM 2 REVIEW EXAM
QUESTIONS AND ANSWERS (VERIFIED
AND UPDATED)
Cell-mediated immunity - ANS - mediated by direct cellular activities (ie. macrophage
hyperactivation, CD8 cytotoxic T cells)
Humoral immunity - ANS - includes antibodies and the cells/pathways they influence
(phagocytosis, neutralization, complement)
- can be passive by transferring antibody containing serum to another individual
What is an extracellular bacterial infection? - ANS - infections where bacteria do not invade
the cells of the host
- antibodies would be most appropriate form of an adaptive immune response
Describe the innate immune response to an extracellular bacterial infection - ANS Innate
immune response:
- at site of tissue damage, resident mast cells release histamine
- complement proteins enter tissue and kill many types of bacteria via alternate pathway
- resident macrophages recognize PAMPs with their PRRs and phagocytose bacteria + produce
alarm cytokines (TNF-alpha, IL-1, IL-6)
- resident macrophages also release substances to recruit neutrophiles and monocytes to site of
infection
@2026/2027 ALLRIGHTS RESERVED.
,Describe the role of dendritic cells in the response to an extracellular bacterial infection -
ANS - immature dendritic cells in the skin engulf bacteria, process is and display it on MHC
class II proteins
- travel to lymph node to present the peptide fragments to a T helper cell
- activate CD4 T helper cells
- produce IL-12 + IL-18
Describe T helper cell effector functions during an extracellular bacterial infection - ANS -
produce IL-2 which supports clonal proliferation
- produce IFN-gamma in response to IL-12 and IL-18 which causes IgG class switch in activated B
cells
Describe cytotoxic T cell effector functions during an extracellular bacterial infection -
ANS N/a
Describe B cell (antibody) effector functions during an extracellular bacterial infection - ANS -
antibodies are carried through the blood to the site of infection
- antibodies are IgM at first, then class switch to IgG which can opsonize and form the
membrane attack complex (MAC)
What is an intracellular bacterial infection? - ANS - where intracellular bacteria invade and
live inside host cells (ie. macrophages)
- bacteria are able to shut down the innate immune responses and reproduce inside the host
cell
- for bacteria that replicate inside macrophages, antibodies would not be useful -> cell-mediate
immune responses are needed (use T cells and macrophages to kill the pathogen)
Describe the innate immune response to an intracellular bacterial infection - ANS - at site of
tissue damage, resident mast cells release histamine
- complement proteins enter tissue and kill many types of bacteria via alternate pathway
@2026/2027 ALLRIGHTS RESERVED.
, - resident macrophages recognize PAMPs with their PRRs and phagocytose bacteria + produce
alarm cytokines (TNF-alpha, IL-1, IL-6)
- resident macrophages also release substances to recruit neutrophiles and monocytes to site of
infection
*when macrophage engulfs the bacteria, the bacteria takes over the cell
- if the macrophage receives special instruction from a T helper cell, it would know that
additional genes are needed to transcribe toxic compounds to kill bacteria
Describe the role of dendritic cells in response to an intracellular bacterial infection - ANS -
immature dendritic cells phagocytose bacteria at site of infection
- travel to lymph node and present peptide on MHC class II proteins to activate T helper cells
- instructs T helper cells to travel to site of infected macrophage -> T helper cell secretes IFN-
gamma at site of infection
Describe how macrophages are super activated - ANS - can be super activated by 2 signals:
T helper cells secrete IFN-gamma and other cytokines (signal 1) and binding of CD40L on T cell
and CD40 on macrophage (signal 2)
Consequences of super activating a macrophage - ANS - macrophages become more effective
at fusing lysosomes with phagosomes
- macrophages increase production of antimicrobial properties (ie. nitric oxide, oxygen radicals
and proteases) *sometimes these compounds leak out of the macrophage and damage the
healthy cells and tissues of the host
- lots of local inflammation
Describe the CD8 T cell effector functions in an intracellular bacterial infection - ANS ?
Describe the B cell (antibody) effector functions in an intracellular bacterial infection - ANS -
less helpful since antibodies cannot access the inside of a cell
@2026/2027 ALLRIGHTS RESERVED.
QUESTIONS AND ANSWERS (VERIFIED
AND UPDATED)
Cell-mediated immunity - ANS - mediated by direct cellular activities (ie. macrophage
hyperactivation, CD8 cytotoxic T cells)
Humoral immunity - ANS - includes antibodies and the cells/pathways they influence
(phagocytosis, neutralization, complement)
- can be passive by transferring antibody containing serum to another individual
What is an extracellular bacterial infection? - ANS - infections where bacteria do not invade
the cells of the host
- antibodies would be most appropriate form of an adaptive immune response
Describe the innate immune response to an extracellular bacterial infection - ANS Innate
immune response:
- at site of tissue damage, resident mast cells release histamine
- complement proteins enter tissue and kill many types of bacteria via alternate pathway
- resident macrophages recognize PAMPs with their PRRs and phagocytose bacteria + produce
alarm cytokines (TNF-alpha, IL-1, IL-6)
- resident macrophages also release substances to recruit neutrophiles and monocytes to site of
infection
@2026/2027 ALLRIGHTS RESERVED.
,Describe the role of dendritic cells in the response to an extracellular bacterial infection -
ANS - immature dendritic cells in the skin engulf bacteria, process is and display it on MHC
class II proteins
- travel to lymph node to present the peptide fragments to a T helper cell
- activate CD4 T helper cells
- produce IL-12 + IL-18
Describe T helper cell effector functions during an extracellular bacterial infection - ANS -
produce IL-2 which supports clonal proliferation
- produce IFN-gamma in response to IL-12 and IL-18 which causes IgG class switch in activated B
cells
Describe cytotoxic T cell effector functions during an extracellular bacterial infection -
ANS N/a
Describe B cell (antibody) effector functions during an extracellular bacterial infection - ANS -
antibodies are carried through the blood to the site of infection
- antibodies are IgM at first, then class switch to IgG which can opsonize and form the
membrane attack complex (MAC)
What is an intracellular bacterial infection? - ANS - where intracellular bacteria invade and
live inside host cells (ie. macrophages)
- bacteria are able to shut down the innate immune responses and reproduce inside the host
cell
- for bacteria that replicate inside macrophages, antibodies would not be useful -> cell-mediate
immune responses are needed (use T cells and macrophages to kill the pathogen)
Describe the innate immune response to an intracellular bacterial infection - ANS - at site of
tissue damage, resident mast cells release histamine
- complement proteins enter tissue and kill many types of bacteria via alternate pathway
@2026/2027 ALLRIGHTS RESERVED.
, - resident macrophages recognize PAMPs with their PRRs and phagocytose bacteria + produce
alarm cytokines (TNF-alpha, IL-1, IL-6)
- resident macrophages also release substances to recruit neutrophiles and monocytes to site of
infection
*when macrophage engulfs the bacteria, the bacteria takes over the cell
- if the macrophage receives special instruction from a T helper cell, it would know that
additional genes are needed to transcribe toxic compounds to kill bacteria
Describe the role of dendritic cells in response to an intracellular bacterial infection - ANS -
immature dendritic cells phagocytose bacteria at site of infection
- travel to lymph node and present peptide on MHC class II proteins to activate T helper cells
- instructs T helper cells to travel to site of infected macrophage -> T helper cell secretes IFN-
gamma at site of infection
Describe how macrophages are super activated - ANS - can be super activated by 2 signals:
T helper cells secrete IFN-gamma and other cytokines (signal 1) and binding of CD40L on T cell
and CD40 on macrophage (signal 2)
Consequences of super activating a macrophage - ANS - macrophages become more effective
at fusing lysosomes with phagosomes
- macrophages increase production of antimicrobial properties (ie. nitric oxide, oxygen radicals
and proteases) *sometimes these compounds leak out of the macrophage and damage the
healthy cells and tissues of the host
- lots of local inflammation
Describe the CD8 T cell effector functions in an intracellular bacterial infection - ANS ?
Describe the B cell (antibody) effector functions in an intracellular bacterial infection - ANS -
less helpful since antibodies cannot access the inside of a cell
@2026/2027 ALLRIGHTS RESERVED.
