The graph below shows the response of the human immune system to exposure to an antigen. Use this graph to answer part a and part b of this question.

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The graph below shows the response of the human immune system to exposure to an antigen. Use this graph to answer part a and part b of this question.


A) Describe the events that occur during period I as the immune system responds to the initial exposure to the antigen. 


B) Describe the events that occur during period II following a second exposure to the same antigen. 


C) Explain how infection by the AIDS virus (HIV) affects the function of both T and B lymphocytes.

A) the first time the body is exposed, selective proliferation and differentiation of lymphocytes occur. Selected B cells produce antibody-secreting effector B cells (plasma cells) and selected T cells are activated to their effector forms. Eventually, T cells clear the antigen from the body.

B) The second time the same antigen is exposed, the response is faster. The antibodies produced in the secondary immune response have a greater affinity for the antigen.Clones of the T and B memory cells generate initial exposure to an antigen. These memory cells proliferate or differentiate faster when they attack the same antigen again.

C) Only T cells are infected resulting in a decrease of T cell population. This decreases B cell proliferation which leads to the decrease of overall immunity. T cell signalling to B cell is also slowed down. The viral glycoproteins bind to CD4 sites of the T4 cell and RME occurs. Also, reverse transcription incorporation of viral genome into lymphocyte genome also occurs. Eventually there is a cell disruption which leads to the death or impaired function of the cell.

Comments

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