Chapter 12 - Lymphoid Tissue

Question 1

Which of the following statements concerning T helper cells is true?
(A) They possess membrane-bound antibodies.
(B) They can recognize and interact with antigens in the blood.
(C) They produce numerous cytokines.
(D) They function only in cell-mediated
immunity.
(E) Their activation depends on interferon-y

Answer 1

C. T helper cells produce a number of cytokines that affect other cells involved in both the cell­ mediated and humoral immune responses. T helper cells possess antigen-specific TCRs (not antibodies) on their membranes. These cells recognize and interact with antigenic determinants that are associated with class II HLA molecules on the surface ofAPCs. IL-l is necessary for activation ofT helper cells (see Chapter 12 II B 3 c).

Question 2

Which of the following statements concerning T cytotoxic (Tc) cells is true?
(A) They assist macrophages in killing microorganisms.
(B) They possess antibodies on their surfaces.
(C) They possess CD8 surface markers.
(D) They possess CD28 surface markers.
(E) They secrete interferon-y.

Answer 2

C. T cytotoxic cells are CDS+ cells. CD28 molecules are present on TH1 cells. IFN-y is released by TH1 cells, which also assist macrophages in killing microorganisms (see Chapter 12 II B 3 c).

Question 3

Which of the following cell types is thought to function in suppressing the immune response?
(A) Inducible T reg cells
(B) B cells
(C) T memory cells
(D) TH cells
(E) Mast cells

Answer 3

A. The immune response is decreased by inducible T reg cells. They suppress the formation of TH1 cells, thereby suppressing the immune response (see Chapter 12 II B 3 c).

Question 4

Which of the following statements concerning interferon-y is true?
(A) It is produced by T memory cells.
(B) It is produced by T reg cells.
(C) It activates macrophages.
(D) It inhibits macrophages.
(E) It induces viral proliferation.

Answer 4

C. Interferon-y activates macrophages, NK cells, and T cytotoxic cells, enhancing their phagocytic or cytotoxic activity or both (see Chapter 12 II E 2).

Question 5

A patient who was given penicillin had an adverse reaction to the antibiotic. Although the reaction was due to the actions of mast cells, the response occurred because mast cells have IgE receptors in their cell membranes. Which of the following cells produced the IgE decorating the plasma cell's surface?
(A) T memory cells
(B) B memory cells
(C) T helper cells
(D) Plasma cells
(E) T cytotoxic cells

Answer 5

D. Individuals allergic to penicillin produce IgE antibodies. The cells that manufacture IgE are plasma cells. After an antigenic challenge, proliferation and differentiation of B cells give rise to plasma cells and B memory cells (see Chapter 12 II C 2).

Question 6

Which of the following statements concerning the thymus is true?
(A) Lymphoid nodules form much of the thymic cortex.
(B) Epithelial reticular cells form Hassall corpuscles.
(C) T cells migrate into the medulla, where they become immunologically competent.
(D) Most T cells that enter the thymus are killed in the medulla.
(E) Macrophages are essential components of the blood-thymus barrier.

Answer 6

B. Epithelial reticular cells of the medulla congregate to form Hassan (thymic) corpuscles (see Chapter 12 VI B 2 b).

Question 7

Which of the following statements concerning Hassan corpuscles is true?
(A) They are located in the thymic cortex of young individuals.
(B) They are located in the thymic cortex of old individuals.
(C) They are derived from mesoderm.
(D) They are located in the thymic medulla.
(E) They are derived from T memory cells.

Answer 7

D. Hassall corpuscles are concentric accretions of epithelial reticular cells (derived from endoderm) found only in the medulla of the thymus (see Chapter 12 VI B 2 b).

Question 8

After their maturation in the thymus and release into the circulation, T lymphocytes migrate preferentially to which of the following sites?
(A) Paracortex of lymph nodes
(B) Cortical lymphoid nodules oflymph nodes
(C) Hilum of lymph nodes
(D) Lymphoid nodules ofthe tonsils
(E) Lymphoid nodules of the spleen

Answer 8

A. T lymphocytes are preferentially located in the paracortex of lymph nodes, whereas B lymphocytes are found in lymphoid nodules located in lymph nodes, tonsils, and the spleen (see Chapter 12 VI A 2 a).

Question 9

In which of the following sites do lymphocytes become immunocompetent?
(A) Germinal center of secondary lymphoid nodules
(B) White pulp of the spleen
(C) Thymic cortex
(D) Red pulp of the spleen
(E) Paracortex of lymph nodes

Answer 9

C. T lymphocytes mature and become immunocompetent in the cortex of the thymus, whereas B lymphocytes do so in the bone marrow. After an antigenic challenge, lymphocytes proliferate and differentiate in various lymphoid tissues (see Chapter 12 II B 2 and II C 1).

Question 10

Which of the following statements about
IgG is true?
(A) It is located in the serum and on the membrane of B cells.
(B) It can cross the placental barrier.
(C) It is involved in allergic reactions.
(D) It exists as a pentamer.
(E) It binds to antigens on the body surface
and in the lumen of the gastrointestinal tract.

Answer 10

B. IgG is the most abundant immunoglobulin isotype in the serum. It can cross the placental barrier but does not bind to the B-cell plasma membrane. It exists as a monomer, functions to activate complement, and acts as an opsonin (see Chapter 12 IV B 2).