Parham Fragen Kapitel 8 Flashcards
All of the following are true in reference to T-cell priming
except _____.
a. it occurs in primary lymphoid organs
b. it transforms naive T cells into differentiated effector T-cells
c. it is the first stage of a primary adaptive immune response
d. it requires interaction between naive T cells and antigen-presenting cells
e. it takes place in many locations including, but not limited to, lymph nodes, Peyer’s patches, and the tonsils
a. it occurs in primary lymphoid organs
Which of the following cell types is unable to interact with naive T cells and induce their activation? (Select all that apply.)
a. B cells
b. macrophages resident in infected tissues
c. macrophages resident in secondary lymphoid tissue
d. interdigitating reticular cells
e. immature dendritic cells
b. macrophages resident in infected tissues
e. immature dendritic cells
When an immature dendritic cell becomes an activated dendritic cell, all of the following changes occur except _____.
a. confinement to T-cell regions of lymph node cortex
b. development of elaborate finger-like processes
c. upregulated expression of MHC class II at the cell surface
d. loss of antigen-processing functions
e. expression of Toll-like receptor TLR9
e. expression of Toll-like receptor TLR9
Identify which of the following statements regarding
naive T cells is incorrect.
a. Naive T cells enter lymph nodes in two different ways, from the blood or from the lymph.
b. Naive T cells can only be activated in secondary lymphoid tissues.
c. Naive T cells differentiate into effector T cells after T-cell priming has occurred.
d. Naive T cells occupy both the cortex and the medulla of lymph nodes.
e. Naive T cells are only activated by dendritic cells, not by macrophages or B cells
d. Naive T cells occupy both the cortex and the medulla of lymph nodes.
Homing of effector T cells to inflamed tissue is facilitated by the upregulation of _____ on the surface of the effector T cell.
a. VLA-4
b. L-selectin
c. CD28
d. VCAM-1
e. B7
a. VLA-4
Identify which of the following statements regarding naive T cells is incorrect.
a. Naive T cells have the capacity to survive for many years as nondividing circulating cells in the absence of specific antigen.
b. Naive T cells express LFA-1 molecules that change their conformation after encountering a specific peptide:MHC complex.
c. Naive T cells exit from lymph nodes using the same route as effector T cells.
d. Naive T cells express ICAM-3, which binds to DC-SIGN on dendritic cells with high affinity.
e. Naive T cells express high levels of S1P receptors on their surface.
e. Naive T cells express high levels of S1P receptors on their surface.
Which of the following statements regarding T cells activated by specific antigen is incorrect?
a. They receive co-stimulatory signals through CD28.
b. They suppress expression of sphingosine 1-phosphate (S1P).
c. They take several days before differentiating into effector T-cells.
d. They cease to secrete and respond to interleukin-2 (IL-2)
e. They begin to express CTLA4, which serves to limit T-cell proliferation
d. They cease to secrete and respond to interleukin-2 (IL-2)
Which of the following explains why dendritic cells, but not macrophages or B cells, contribute to the activation of naive T-cells?
a. Macrophages and B cells do not express MHC class II molecules until they are activated
b. Dendritic cells upregulate B7 after engaging innate immunity receptors at sites of infection
c. Dendritic cells express higher levels of CTLA4
d. Macrophages and B cells do not process antigen
e. Dendritic cells use Toll-like receptors to hold antigen in place for extended periods of time
b. Dendritic cells upregulate B7 after engaging innate immunity receptors at sites of infection
If CD4 or CD8 co-receptors are absent, then approximately _____ specific peptide:MHC complexes are needed to activate a T cell.
a. twice the number of
b. 10 times the number of
c. 20 times the number of
d. 100 times the number of
e. 1000 times the number of
d. 100 times the number of
Cyclosporin A is an immunosuppressive drug commonly used in transplant patients to prevent graft rejection by alloreactive T cells. It acts by interfering with the signaling pathway that leads from the T-cell receptor to transcription in the nucleus of the genes for the cytokine IL-2 and the α chain of the IL-2 receptor. Why does preventing the transcription of these genes lead to immunosuppression?
In an immune response, the binding of IL-2 to a high-affinity IL-2 receptor composed of α, β, and γ chains drives the proliferation and differentiation of T cells that occurs after they have encountered their specific antigen. The activated T cell will divide two to three times daily for about a week, producing a clone of thousands of identical antigen-specific effector T cells. The α chain is required to form a complex with preexisting γ and β chains to make the high-affinity receptor. The receptor formed by the γ and β chains only has a low affinity for IL-2. In the absence of IL-2 and its high-affinity receptor, T cells will not be fully activated, will not differentiate, and will not undergo clonal expansion. Thus, by preventing the production of IL-2 and its receptor, cyclosporin A prevents the clonal expansion of T cells specific for the foreign antigens on the graft and their differentiation into effector T cells, and thus suppresses the immune response directed against the graft.
Antigen recognition by T cells in the absence of co-stimulation results in
a. upregulation of B7
b. expression of the high-affinity IL-2 receptor
c. T-cell anergy
d. T-cell apoptosis
e. phosphorylation of immunoreceptor tyrosine-based activation motifs
c. T-cell anergy
_____ cells remain in, rather than leave, the secondary
lymphoid organs in which they differentiated.
a. CD4 TH1 cells
b. CD4 TFH cells
c. CD8 cytotoxic T cells
d. Regulatory CD4 T cells
e. All of the above
b. CD4 TFH cells
Match the T-cell type in column A with its correct description in column B.
a. regulatory T cells (Treg)
b. CD8 T cells
c. CD4 TH1 cells
d. CD4 TH2 cells
e. CD4 TH17 cells
- help basophils, mast cells, eosinophils and B cells respond to parasitic infections
- facilitate neutrophil response to fungal and extracellular bacterial infections
- suppress effector CD4 and CD8 T-cell function
- differentiate under the influence of IL-12 and IFN-γ
- induce apoptosis of target cells after targeted delivery of cytotoxins
a—3
b—5
c—4
d—1
e—2
Linked recognition is best described as _____.
a. the delivery of the co-stimulatory signal by antigen-presenting cells to T cells
b. cooperation between T follicular helper (TFH) and naive B-cells bearing specificity for different epitopes of the same antigen and where the B cell serves as the antigen presenting cell
c. the linking of Toll-like receptors and the innate immune response
d. the interaction between processed antigenic peptides and MHC molecules during antigen presentation
e. the region of contact between T cells and antigen-presenting cells involving cell-adhesion molecules and other cell-surface receptor-ligand pairs
b. cooperation between T follicular helper (TFH) and naive B-cells bearing specificity for different epitopes of the same antigen and where the B cell serves as the antigen presenting cell
Vijay Kumar, a 19-year-old male who had emigrated to the United States from South India two years before, developed lesions in his nasal mucosa, and nodular skin lesions on his cheeks and buttocks. Examination of a stained biopsy of a skin lesion revealed numerous clumps of mycobacteria. T cells in the skin lesions were secreting IL-4, IL-5, and IL-10. What would be the most likely diagnosis?
a. tuberculosis
b. lepromatous leprosy
c. leishmaniasis
d. tuberculoid leprosy
e. allergic dermatitis
The correct answer is b. Leprosy, caused by Mycobacterium leprae, can come in two forms. Lepromatous leprosy is characterized by a bias toward TH2 cells, which produce the cytokines IL-4, IL-5, and IL-10. In contrast, tuberculoid leprosy is associated with a bias toward TH1 cells, which characteristically produce IL-2, IFN-γ, and lymphotoxin (LT). The location of the lesions on Vijay’s extremities is also consistent with an infection with M. leprae rather than with M. tuberculosis (which causes tuberculosis), because M. leprae grows optimally at 30°C whereas M. tuberculosis grows best at 37°C and primarily causes lung disease.
Vijay most probably contracted M. leprae in an area of South India where leprosy is endemic before his emigration to the United States.
