A set of mice are each immunized with one of the following as shown in the Figur

Question

A set of mice are each immunized with one of the following as shown in the Figure below

Mouse A is immunized with tetanus toxoid protein. Mouse B is immunized with the Haemophilus influenzae type b polysaccharide antigen. Mouse C is immunized with a conjugate of the diphtheria toxoid protein linked to H. influenzae type b polysaccharide. Mouse D is left unimmunized (naive). Four weeks later the spleen cells from each mouse are isolated, and B lymphocytes and T lymphocytes from each spleen cell population are purified. When mixed together in culture together with a conjugate antigen of the tetanus toxoid protein linked to the to H. influenzae type b polysaccharide. Which of the following combinations of spleen cells would generate a memory B cell response?

Explanation / Answer

B lymphocytes from mouse B plus T lymphocytes from mouse B

B lymphocytes from mouse A plus T lymphocytes from mouse A

B lymphocytes from mouse B plus T lymphocytes from mouse D

B-cells receive signals from T-cells that have encountered the same antigen (T-cell dependent response). Memory B -cells are produced when plasma cells receive signals from TH cells. The plasma cells that secrete high affinity antibodies receive signals from TFH cells . The cells express CD40L, which interacts with CD40 of B-cells and drives the cell into cell cycle.

Since the antigen of H. influenzae is a capsular antigen (carbohydrate), its responses does not require participation of T cells. The B cells can activate through direct interaction with the carbohydrate antigen. Therefore, a T-independent response is generated.

B lymphocytes from mouse A plus T lymphocytes from mouse A

B lymphocytes from mouse B plus T lymphocytes from mouse D

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