1.consider the figure above that shows time on the X axis and number of antigen-

Question

1.consider the figure above that shows time on the X axis and number of antigen- specific adaptive immune cells on the Y- axis. This figure provides a general accounting of an adaptive immune response that can be broken down into five stages.

a. what is happening in stages 1 &2 that increases the number of cells ?

b. what is happening to cells after 2 to cause a reduction of cell numbers?

c. sometimes( usually rarely), the number of antigen- specific cells does not decline as shown in stages 3&4. Consider the underlying reason for the normal decline in cell number and propose a scenario in which the normal decline would not happen.

Phases of adaptive immune responses Contraction Activation phase Antigen Recognition phase elimination (homeostasis) y Memory Antibody producing. Effector T cell | Elimination lymphocyte of antigens Differentiation Humoral immunity Cell-mediated immunity Surviving memory cells Antigen presenting cell Apoptosis Clonal expansion Naive T lymphocyte Naive B lymphocyte Days after antigen exposure 7 Need for proliferation and differentiation results in delay (typically 4-7 days) in the adaptive immune response

Explanation / Answer

in this figure different stages of adaptive immune responses. this response composed of separate phases.

a) in stage1, antigen identification takes place and stage2 shows the lymphocyte activation. matured naive cells left the bone marrow and thymus and entered the lymphatic system to encounter the antigen, that is why increase in cells takes place.

b) after stage2, elimination of antigen takes place, it is also known as effector phase i.e. activated by the antigen and eliminate the antigen

c) decline of response is due to death of lymphocyte (stimulated by an antigen) by apoptosis, homeostasis is restored and those cells that survive are long lived become memory cells. decline shows the normal ommune rsponse.

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