What are NKT cells?

Question 1 of 5

What are NKT cells?

A. T cells that recognize lipids presented by CD1-MHC molecules B. A combination of NK cells and T cells C. T cells with non-traditional TCRs D.

Correct Answer: A

Rationale: NKT cells recognize lipids via CD1 ; they share NK and T-cell traits but are defined by CD1 specificity.

Question 2 of 5

Vaccines generally confer what type of immunity?

A. artificially acquired passive immunity B. artificially acquired active immunity C. naturally acquired passive immunity D. naturally acquired active immunity

Correct Answer: B

Rationale: Vaccines stimulate active immunity artificially ; passive (A, C) involves antibody transfer, natural active is from infection.

Question 3 of 5

Naive B and T lymphocytes are small, quiescent cells with little cytoplasm and low metabolic activity. Yet within hours after being activated following encounter with their antigen, these cells enlarge and up-regulate many biosynthetic and metabolic pathways. Approximately one day later, the cells begin dividing, and for several days they are the most rapidly dividing cells in the body, undergoing 2-4 rounds of cell division every day. In order to maintain this phenomenal rate of cell division, lymphoblasts must:

A. Use the large energy stores accumulated by them when they were naive quiescent cells prior to their activation B. Engulf their neighboring small quiescent lymphocytes in order to take their lipids and proteins for raw material C. Up-regulate synthesis of mRNA and proteins, some of which encode for glucose transporters and enzymes used for glycolysis D. Phagocytose extracellular proteins and lipids and degrade them for energy production

Correct Answer: C

Rationale: Lymphoblasts up-regulate glycolysis via glucose transporters/enzymes ; naive cells lack stores , don't engulf lymphocytes , or phagocytose broadly .

Question 4 of 5

Immunodeficiency diseases occur when individuals have defects in leukocyte adhesion to inflamed endothelial cells, thereby impeding the extravasation of phagocytes into infected tissues. When neutrophils from one class of these patients were isolated and tested using in vitro assays for neutrophil-endothelial cell interactions and extravasation, it was found that the neutrophils could slowly roll along the endothelial vessel wall but were unable to arrest and migrate across the endothelium. The most likely protein deficient in these neutrophils is:

A. ICAM-1 or ICAM-2 B. P-selectin C. E-selectin D. An integrin

Correct Answer: D

Rationale: Integrins mediate neutrophil arrest; rolling (selectins, B/C) occurs, but without integrins, migration fails; ICAMs are on endothelium.

Question 5 of 5

The adaptive immune system uses multiple strategies to generate diversity in our ability to mount responses to a wide array of infectious microorganisms. These strategies include the generation of diverse repertoires of B-cell and T-cell antigen receptors, as well as polymorphism of MHC genes. The polymorphism of MHC genes differs from the diversity of lymphocyte antigen receptors in that:

A. It involves DNA rearrangements at multiple gene segments in the MHC locus B. It requires different enzymes than the RAG1/RAG2 recombinase required for antigen receptor rearrangements C. It results in a diverse repertoire of clonally distributed receptors on dendritic cells, rather than on lymphocytes D. It creates diversity between individuals in the population rather than within a single individual

Correct Answer: D

Rationale: MHC polymorphism varies between individuals ; receptor diversity is clonal within one (A, B, C are incorrect).

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