PRACTICE MCQ Humoral Immunity Flashcards
A 24-year-old patient recovers from a motor vehicle accident but requires a splenectomy. The doctor informs him that he can lead a normal life but will require which of the following?
a. passive immunizaition with gamma globulin
b. regular transfusions
c. careful monitoring of lymph nodes for enlargement
d. immunization against encapsulated organisms
D.
The spleen is a major source of marginal zone B cells, which provide early responses to bacteria, particularly encapsulated species. Protection against these organisms is best accomplished by active immunization. Although the spleen is a reservoir for platelets a splenectomized patient will not have decreased counts and will not require transfusions.
Without CD40L-CD40 interaction, B lineage cells fail to undergo which of the following?
a. development from pro-B cell
b. immunoglobulin gene rearrangement
c. class isotype switch
d. formation of an antigen specific receptor
C.
CD40-CD40L interaction between B and T cells is necessary for germinal center formation and events in the germinal center, including class switching
A 4-year-old boy has a large posterior auricular (behind the ear) lymph node following a middle ear infection. Streptococcus pneumoniae is the causative agent. If you analyzed the draining lymph node you would expect to find which of the following?
a. dendritic cells and B cells specific for S. Pneumoniae
b. T and B cells specific for S penumoniae
c. B cells specific for S pneumoniase producing immunoglobulin with only one type of light chain
d. large bacterial colonies growing in the lymph nodes
c.
d.
B.
Both the T cells and B cells will be specific for the organism, although for different epitopes of the bacteria. Dendritic cells are not antigen specific but rather display a variety of antigen epitopes.
A 20-year-old woman has a screening ultrasound at 18 weeks gestation that shows fetal hydrops. Serologic testing is performed on maternal serum (‘TORCH titers’). The serologic testing can differentiate a recent infection from a past infection. This differentiation is most likely to be based upon which of the following immunologic mechanisms?
a. Ag presentation by dendritic cells
b. antibody feedback
c. heavy chain class switching
d. somatic hypermutation
c. secondary antibody response
C.
This is the basis for measuring IgM and IgG responses. Presence of IgM suggests recent infection before the switch to IgG occurs. If just IgG is present, then the infection occurred at some point in the past.
In an experiment, bacteria growing in culture are used to stimulate antibody production. It is observed that heavy chain class switching does not occur in response to the bacterial stimulus. By display of which of the following substances do the bacteria activate the B cells?
a. complement C5-9
b. IL-12
c. mRNA
d. peptides displayed by MHC 2 molecules
e. polysaccharide
E.
Non-protein antigens (characteristic for many bacteria) stimulate a response that does not rely on interaction with helper cells
T INDEPENDENT
In a study of infections, microbial antigens are observed to stimulate antigen-specific B cells. These B cells proliferate to produce antibodies. In which of the following locations are thesee antigens most likely to initially encounter corresponding specific clones of B cells?
a. germinal center
b. lymph node follicle
c. spleen
d. mucosal surface
e. thymic medulla
B.
follicles within lymph nodes are where antigen presenting cells such as dendritic cells are located
In an experiment, complement is activated via the classic pathway from presence of mannose-binding lectin contacting bacterial organisms. It is observed that B cells become activated. Type 2 complement receptor (CR2), attached to CD19 helps to initiate B cell activation. Binding of which of the following complement components to the CR2 and CD19 is most likely to cause this activation?
a. C1q
b. C3b
c. C3d
d. C5a
d. C9
C
See your notes on 2nd signal required to activate B cells.
The CD19 antigen (along with CD20) is one of the most often utilized markers for B cells. When complement receptors do not function appropriately, then there is immune dysfunction
. The increased B7 expression leads to activation of additional cells. Which of the following cell types is most likely to be activated by B7 expressed by B cells?
a. B cell
b. NK cell
c. CD4 cell
d. CD8 cell
e. Plasma cell
C.
The B cells and the CD4 ‘helper’ cells have significant interaction
In a study of B cell activation, it is shown that B cells can be stimulated to produce IgG that can bind to both Fc receptors on macrophages and to bacterial organisms. Which of the following substances is most likely to stimulate B cells to produce IgG with these properties?
a. C3d
b. IFNy
c. IL-5
d. IL-12
e. IgM
B.
IFN-y would do this, since it also activates the macrophages
A 25-year-old man receives the series of hepatitis B vaccinations. Ten years later he has a serologic test positive for hepatitis B surface antibody). This antibody is most likely produced by which of the following cells?
a. Naive B cells in circulation
b. IgM secreting B cells in lymph nodes
c. IgA secreting B cells in serum
d. IgG secreting plasma cells in marrow
e. Kupffer cells in the liver
D.
These cells hang around for decades, producing small amounts of immunoglobulin, which is the basis for the protection from the immunization. The purpose of a ‘booster’ shot for some vaccines is the re-introduction of antigen that further stimulates an immune response to increase levels of antibody production.
A clinical study is conducted with subjects who have bacterial pneumonias. It is observed that, after the infectious process has abated and they are getting well, the amount of immunoglobulin produced in the body is decreasing. By which of the following mechanisms is this decrease in immunoglobulin production most likely to occur?
a. Antibody attaches to B cell Fc receptors
b. B cells stop producing MHC II molecules
c. IFNy binds to macrophages
d. CD4 cells increase CD40L expression
e. heavy chain class switching to IgM occurs
A.
By attaching to these receptors, signals to antigen receptors are inhibited and the immune response is turned off. This happens when most of the antigen has been neutralized, with a succesful immune response
AB NEGATIVE feedback
In an experiment, bacterial organisms are added to whole human blood. It is shown that the bacterial organisms become opsonized. The opsonized bacteria are observed to be phagocytized by neutrophils. Which of the following components of the immunoglobulin molecules on these bacteria is most likely to lead to phagocytosis?
a. disulfide bond
b. Fab region
c. Fc portion
d. heavy chain
e. light chain
C.
EFFECTOR fxn occurs through Fc receptors
In an experiment, bacteria are added to whole human blood. It is observed that the the bacteria become opsonized and phagocytized. When the experiment is repeated with blood from which all specific antibody has been removed, the bacteria still become phagocytized. Phagocytic cells have absence of specific antibody, bacteria can still be opsonized and then phagocytized. Which of the following receptors do these phagocytes most likely have?
a. CD3
b. CD40
c. CR1
d. Fc
e. IgB
c.
The CR1 on RBCs can recognize C3b coating microbes.
A 12-year-old girl has had episodes of marked edema of her face and extremities for the past 7 years. Some of these episodes have included life-threatening laryngeal edema. In other episodes she has had diarrhea. She does not have a history of recurrent infection. Her condition is improved with use of stanozolol and danazol. She is most likely to have an inherited deficiency of which of the following?
a. C1 NIH
b. CD40L
c. neutrophils
d. IgE
e. Histamine
A
condition known as hereditary angioneurotic edema and results when the inhibitor is not around to prevent activated complement components from forming that lead to vasoactive processes.
deficiency in C1 inhibitor
bradykinin remains active
In a clinical trial, polio vaccine is found to be most effective when administered orally. This oral vaccine is most likely to elicit which of the following protective immune responses?
a. antigen gathering dendrtici cells
b. binding IgE to mast cells
c. CD4 cell proliferation in gut associated lymphoid tissue
d increased memory B cells
e. mucosal IgA secretion
E.
Polio is an enterovirus that is ingested. Mucosal immunity is mainly a function of IgA secretion. The IgA neutralizes the viral particles before they can establish an infection
