Introductory Biology: 100-Word Response
Sample Low-Stakes Assignment from Professor David Abbott, University of Wisconsin-Madison
In your own words, and in complete sentences totaling no more than 100 words, discuss why the function of the dendritic cell can be likened to the famous midnight ride of Paul Revere on the night of 18th of April 1775. During these excursions, Revere warned the Massachusetts countryside that the British were coming. Include in your answer HOW aspects of the innate and acquired immune responses, and particularly CD4+ (or helper) T cells, fit into the analogy. Remember, I want to know more about the immunology than the history!
If you want to refresh your memory of the role played by Paul Revere in the American War of Independence (or American Revolutionary War), by all means visit the following website: http://en.wikipedia.org/wiki/Paul_Revere
Sample Student Answer #1:
Dendritic cells are the “Paul Revere” cells because they warn and alert the rest of the immune system that an invader is inside the body. Dendritic cells display antigen fragments on their class II MHC molecules. Helper T cells then bind to the “flagged” dendritic cell using its T-cell receptor and CD4 molecule forming the immune synapse. The dendritic cells give the T cell the cytokine “message” through the synapse and the T cell activates and releases cytokines arbitrarily. The T cell then undergoes clonal selection and also further goes on to activate the humoral and cell mediated responses.
Instructor Feedback: Nice answer. You are on the right track.
Sample Student Answer # 2:
Once Paul Revere learned of the bad news, he rode to Lexington warning people of the countryside along the way. Much like Paul, a dendritic cell migrates from peripheral tissues through the lymphatic vessels to the lymph nodes (Lexington) once it ingests a pathogen. This is part of the innate immunity system. By releasing cytokines (analogous to Revere’s warnings) the cell signals for a helper T cell to bind to its TCR and form an immune synapse. This stimulates the T cell to proliferate and form effector cells and memory cells (acquired immunity) in order to combat future invaders, much like the rallying of the American army against the British.
Instructor Feedback: You omitted the dendritic cell attracting binding of helper T cell receptor
Sample Student Answer #3:
Like Paul Revere, dendritic also send messages of foreign invaders, specifically between the innate and acquired immunity. With the innate immunity, they are on the look-out on tissue surfaces for any foreign antigens (Brits), capture them via phagocytosis (acquire information), and move them to lymphoid tissue (cities in Massachusetts). The antigens are presented to helper T cells (information told to other Yankees) via Class II MCH molecules (lanterns), bound by the T cell receptor and CD4 receptor. The acquired immunity is initiated for a response to fight the antigen (troops are round up to fight the Brits).
Instructor Feedback: You omitted the immune synapse and/or dendritic cell releasing cytokines.
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