Thursday, March 11, 2004

Each multiple choice question has one answer unless indicated otherwise at the end of the question

1. If a fully mature autoreactive B-lymphocyte leaves the bone marrow and is not anergic, what will happen if that B-cell forms high affinity bonds with the self-antigen for which it is specific? (one answer)

A. it will then become anergic, rendering it unable to respond

B. it will die (by apoptosis)

C. it will respond

D. it will cease to express B7 molecules

2. Initiation of B-cell development eventually stimulates initiation of gene fragment somatic recombination for heavy and light chains. These recombination events occur within the nucleus and are started when which one of the following is activated?

A. recombinant activation genes (RAG)

B. Ig-alpha and Ig-beta trans nuclear membrane "tails"

C. apoptosis-inducing nucleoside sequences

D. B7

3. Elimination of autoreactive T-cytotoxic lymphocytes ("negative" selection) occurs when which one of the following conditions is met?

A. high affinity bonds form between the T-cell antigen receptor and an antigen presented by an MHC Class II

B. at the same time that the T-cell becomes "restricted" with regard to the MHC Class I molecules that can successfully present peptides to the autoreactive T-cell

C. high affinity covalent bonds form between the T-cell antigen receptor and an antigen presented by a MHC Class I

D. high affinity non-covalent bonds form between the T-cell antigen receptor and an antigen presented by a MHC Class I

4. Which one of the following types of cells is encountered first as a stem cell begins to move through the thymus during its development into a fully functional T-cytotoxic cell?

A. cortical epithelial cells

B. double-positive dendritic cells

C. macrophages presenting very large numbers of peptides using MHC Class II

D. stromal cells expressing Kit and SCF, and also secreting IL-7

5. The original source of the dendritic cells and macrophages that are found in the medulla of the thymus is which one of the following?

A. the cortex of the thymus (the cells simply move inward to the medulla and prepare to participate in negative selection)

B. the bone marrow (same area from which the stem cells originate that will eventually become T-cells)

C. they are permanent residents of the thymus medulla (i.e., are "born" there) and remain in the medulla to participate in positive selection

D. the spleen (which is often an ignored organ when the immune system is studied in detail)

6. The cell that is most directly responsible for initiating B-cell development and several of the early steps in that development is which one of the following?

A. dendritic cell

B. epithelial cell (in the cortex)

C. endothelial cell expressing high levels of VCAM-1

D. stromal cell

7. There is a series of cell-cell interactions during B-cell development that involve surface molecules of both the B-cell and the cell that initiates the development process. Which one of the following is an example of one of those surface-surface interactions?

A. IL-7 and IL-7 receptor

B. Kit and SCF

C. MHC Class I and CD8

D. heavy chain and surrogate light chain

8. MHC restriction refers to a process that takes place during T-cell development that ensures a proper "fit" between which TWO of the following? (select TWO answers that are correct)


B. the T-cell antigen receptor


D. CD28

9. The appearance of which one of the following on the surface of a developing B-lymphocyte indicates that a heavy chain has been successfully produced, but creation of a light chain has not begun?

A. functional antigen receptors of the IgM isotype (monomeric form)

B. a non-functional receptor-like molecule (2 heavy chains and 2 surrogate light chains)

C. a non-functional receptor-like molecule (1 beta chain and 1 surrogate alpha chain)

D. a non-functional receptor-like molecule with 2 complete, functional Fab portions

10. Good cell adhesion is very important to cells that are interacting with each other. Often the interactions between two surface molecules on two interacting cells will alter other sets of interacting molecules and affect the overall adhesion of the two cells. For example, when a T-cell receptor forms high affinity bonds with a peptide presented by an MHC and the CD molecule also forms bonds with the same MHC, nearby LFA-1 and ICAM-1 molecules are affected in which one of the following ways?

A. these two surface molecules form even stronger bonds

B. the LFA-1 disappears, and is replaced by a much higher affinity IL-7 receptor

C. these two surface molecules dissociate, and the