Question

Pick blood OR lymph to fill in the following blanks. (1 point) Once T and B cells mature they circulate through the body in (a)_____________ vessels. Dendritic cells that encounter a pathogen in the tissue and became activated traffic to the draining lymph node via a (b)_____________ vessel. Once a T cell is activated in the lymph node it enters a (c)____________ vessel to travel and migrate into the infected tissue.

2. True or False: Tertiary lymphoid organs can form at mucosal sites that have a high exposure to microbes and can activate adaptive immunity. (1 point) a. True b. False

3. Macrophagesanddendriticcellsareinthetissueandnotcirculatingintheblood stream; what cell present in the blood migrates into the tissue to differentiate into macrophages and dendritic cells? (1 point) a. Basophils b. Monocytes c. Lymphocytes d. Eosinophils

4. ShortAnswer:Name and describe the shared mechanism that increases the diversity of the BCR, antibody and TCR repertoire. Outline the general sequence of events in this mechanism in either the development of antibody producing B cells or T cells that allows for the diversification of the antigen binding receptors in lymphocytes. (2 points)

5. ShortAnswer:What is the affinity hypothesis for T cell development?Briefly describe 3-4 main outcomes for T cells proposed by this model. (1 point)

6. ShortAnswer:Define central tolerance and peripheral tolerance of B cells to antigen (include location and the overall outcome of tolerance) (2 points).

7. ShortAnswer:Describe two mechanisms of B cell tolerance( include antigen type). Why are these important processes in the development of B cells? (2 points)

Answer 1

1.a)Blood. After maturity, the B and T cells enter the bloodstream and move towards the peripheral lymphoid organs.

b)Lymph. Dendritic cells that circulate in the blood do not have all the typical features of their counterparts in tissue, that is they are less mature and have no dendrites. After getting activated they travel to lymph nodes through the lymphatic system.

c)Lymph. After the maturity and getting activated, the T cells move out from the lymph nodes as effector cells through the efferent lymphatic vessel to reach the site of infection.

2. True. Recent studies have shown that the tertiary lymphoid organs present at the site of high microbial exposure could contribute to adaptive immunity. Although TLOs within tissues show varying degrees of organization, they frequently display evidence of segregated T and B cell zones, follicular dendritic cell networks, a supporting stromal reticulum, and high endothelial venules. In this respect, they mimic the activities of germinal centers and contribute to the local control of adaptive immune responses

3. Monocytes. Monocytes circulate in the bloodstream for about one to three days and then typically move into tissues throughout the body where they differentiate into macrophages and dendritic cells. They can differentiate into inflammatory DCs or macrophages during inflammation, and possibly, less efficiently, in the steady-state. Basophil and eosinophil are not subjected to further differentiation.

5. The affinity hypothesis suggests that TCRs with low affinity for self-antigen are selected to survive. They are primed for interaction with foreign antigen (positive selection), while TCRs with high affinities for self-peptide are sentenced to death (clonal deletion) or enter an anergic state.