Concept explainers
Upon first exposure to an antigen, a sequence of events results inantigen processing and an increase in the number of helper T cells. Given the following list of events, select the sequence that results in an increased number of helper T cells.
(l) Unprocessed extracellular antigen is ingested by a macrophage.
(2) The MHC II complex is presented at the cell surface.
(3) Costimulation occurs.
(4) Interleukin-1 is released from macrophages, and interleukin-2 isreleased from T lymphocytes.
(5) A specific helper T cell recognizes and binds to the MHC II complex.
(6) Mitosis of helper T cells takes place.
(7) The ingested antigen is broken down to fragments,
(8) The processed antigen and MHC II molecules are joined and transported to the cell surface.
a. 1,7,8,2,5,3,4,6
b. 1,7,8,5,2,3,4,6
c. 7,8,1,2,5,3,4,6
d. 1,2,5,3,4,6,7,8
e. 1,8,7,2,3,5,6,4
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SEELEY'S ANATOMY+PHYSIOLOGY
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