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Match the immunodeficiency with its corresponding cause or consequenceز

Premises
DiGeorge syndrome
APECED
Bare lymphocyte syndrome
IL-7 receptor deficiency
IPEX
Responses
absence of functional AIRE
absence of functional FoxP3
absence of T cells due to absence of thymus
absence of T cells because of signaling defects by thymic stromal ells
absence of functional MHC class I or MHC class II molecules

Correct Answer

DiGeorge syndrome
APECED
Bare lymphocyte syndrome
IL-7 receptor deficiency
IPEX

Which of the following statements is correct?


A) In adults the mature T-cell repertoire is self-renewing and long-lived and does not require a thymus for the provision of new T cells.
B) T cells and B cells are both short-lived cells and require continual replenishment from primary lymphoid organs.
C) The human thymus is not fully functional until age 30,at which time it begins to shrink and atrophy.
D) In DiGeorge syndrome the bone marrow takes over the function of the thymus and produces mature peripheral T cells.
E) None of the above statements is correct.

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The T-cell receptor β-chain locus can undergo successive gene rearrangements to rescue unproductive V(D)J rearrangements. A.What aspects of gene segment rearrangement at the TCRβ locus make this possible? B.Can the immunoglobulin heavy-chain locus,which is also composed of V,D,and J segments,undergo successive rearrangements? If not,give the reasons for the difference.

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A.Successive gene rearrangement is possi...

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Which of the following is the first stage of T-cell receptor gene rearrangement in α:β T cells?


A) Vα→Dα
B) Dα →Jα
C) Vβ→ Dβ
D) Dβ→Jβ
E) Vα→Jα.

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Autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy (APECED) is caused by a defect in


A) cathepsin L
B) a transcription factor that regulates tissue-specific gene expression in the thymus
C) the production of regulatory CD4 T cells
D) FoxP3
E) T-cell receptor gene rearrangement.

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B

Individuals with a defective autoimmune regulator gene (AIRE) exhibit


A) DiGeorge syndrome
B) autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy (APECED)
C) severe combined immunodeficiency (SCID)
D) MHC class I deficiency
E) MHC class II deficiency.

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If a double-negative thymocyte has just completed a productive β-chain gene rearrangement,which of the following describes the immediate next step in the development of this thymocyte?


A) A pre-T-cell receptor is assembled as a superdimer.
B) Rearrangement of γ- and δ-chain genes commences.
C) Expression levels of RAG-1 and RAG-2 are elevated.
D) The linked δ-chain genes are eliminated.
E) This cell will inevitably differentiate into a committed γ:δ T cell.

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In which of the following ways does the developmental pathway of α:β T cells differ from that of B cells? (Select all that apply.)


A) Their antigen receptors are derived from gene rearrangement processes.
B) When the first chain of the antigen receptor is produced it combines with a surrogate chain.
C) Cells bearing self-reactive antigen receptors undergo apoptosis.
D) MHC molecules are required to facilitate progression through the developmental pathway.
E) T cells do not rearrange their antigen-receptor genes in the bone marrow.

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Which of the following cell-surface glycoproteins is characteristic of stem cells,but stops being expressed when a cell has committed to the T-cell developmental pathway?


A) CD2
B) CD3
C) CD25
D) CD34
E) MHC class II.

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Giulia McGettigan was born full term with a malformed jaw,cleft palate,a ventricular septal defect,and hypocalcemia.Within 48 hours of birth she developed muscle tetany,convulsions,tachypnea,and a systolic murmur.A chest X-ray showed an enlarged heart and the absence of a thymic shadow.Blood tests showed severely depleted levels of CD4 and CD8 T cells; B-cell numbers were low but within normal range.Parathyroid hormone was undetectable.Fluorescence in situ hybridization of the buccal mucosa revealed a small deletion in the long arm of chromosome 22.Giulia failed to thrive and battled chronic diarrhea and opportunistic infections,including oral candidiasis and Pneumocystis jirovecii,the latter infection causing her death.Giulia most probably had which of the following immunodeficiency diseases?


A) AIDS
B) DiGeorge syndrome
C) bare lymphocyte syndrome
D) chronic granulomatous disease
E) hyper IgM syndrome.

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Which of the following statements regarding positive selection is correct?


A) All subsets of developing T cells undergo positive selection before export to the peripheral circulation.
B) T-cell receptor editing is linked to the process of positive selection.
C) Positive selection results in the production of T cells bearing T-cell receptors that have the capacity to interact with all allotypes of MHC class I and class II molecules,and not just those of the individual.
D) Positive selection ensures that autoreactive T cells are rendered non-responsive.
E) If there is a genetic defect in AIRE,then T-cell development is arrested as positive selection commences.

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A.What is the role of regulatory CD4 T cells (Treg)? B.How can Treg be distinguished from other non-regulatory CD4 T cells?

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A.Treg suppress the proliferation of naive ...

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Thymocytes that are not positively selected


A) undergo genetic reprogramming and differentiate into a different cell type
B) are exported to the periphery,where they are phagocytosed by macrophages
C) make up about 98% of developing thymocytes and die by apoptosis in the thymic cortex
D) are eliminated because of their reactivity with self antigens
E) try out different β chains to acquire reactivity with self-MHC molecules.

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C

MHC class II deficiency is inherited as an autosomal recessive trait and involves a defect in the coordination of transcription factors involved in regulating the expression of all MHC class II genes (HLA-DP,HLA-DQ,and HLA-DR). A.What is the effect of MHC class II deficiency? B.Explain why hypogammaglobulinemia is associated with this deficiency.

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A.MHC class II deficiency affects the de...

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Genetic deficiencies in all of the following would impair the development of a fully functional T-cell repertoire except


A) RAG-1 or RAG-2
B) Notch1
C) Pax-5
D) IL-7 receptor (CD127)
E) TAP-1 or TAP-2.

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C

Immediately after positive selection


A) the thymocyte reaches maturity and is exported to the periphery
B) RAG proteins are degraded and are no longer synthesized
C) receptor editing commences to eliminate reactivity against self antigens
D) the developing thymocyte acquires a double-negative phenotype
E) expression of pTα is repressed.

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Which of the following is mismatched:


A) double-negative CD3- thymocytes: cortico-medullary junction
B) double-negative CD3- thymocytes: subcapsular zone
C) double-positive CD3+ thymocytes: cortico-medullary junction
D) cortical epithelial cells: subcapsular regions
E) dendritic cells: cortico-medullary junction.

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Identify which of the following describes how antigen processing and presentation of self antigens by thymic epithelial cells differs from that of antigen-presenting cells in peripheral tissues.(Select all that apply.)


A) Thymic epithelium expresses MHC class I molecules but not MHC class II molecules.
B) Thymic epithelium uses cathepsin L for proteolytic degradation of self proteins.
C) Thymic epithelium expresses MHC class II molecules but not MHC class I molecules.
D) Thymic epithelium uses the transcription factor AIRE to activate thymic expression of tissue-specific genes.
E) Thymic epithelium expresses transcription repressor protein FoxP3.

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If the process of positive selection did not occur,then


A) a condition resembling immune dysregulation,polyendocrinopathy,enteropathy,X-linked syndrome (IPEX) would develop
B) a condition resembling autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy (APECED) would develop
C) naive T cells would be unable to undergo differentiation in secondary lymphoid tissues
D) malignant transformation would be more likely because of the accumulation of multiple mutations
E) only a very small percentage of circulating T lymphocytes would be able to become activated.

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A.What is Notch1? B.Which cells express the ligand of Notch1? C.How does the interaction between Notch1 and its ligand mediate T-cell development?

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A.Notch1 is a membrane-bound receptor fo...

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