1. Briefly describe two functions (end results) of the complement system which are the most important to health. What is the evidence for their importance? Mention the complement components central to each function. (15 points)
The two most important functions are opsonization and immune-complex removal. You lost 2 points for each of these you didn't choose. Immune complex disease is very serious. Other important but less important functions are anaphylatoxins and MAC. Remember that C9 deficiency produces no symptoms and deficiency of any component necessary for MAC produces relatively minor problems with Neisseria.
Jackie Nasuti wrote this nice answer on opsonization. I have edited it slightly.
"Opsonization, which is caused by C3bi, is one of the most important activities of the complement system. When C3bi, being an opsonin, is covalently bound to a microbe, macrophages phagocytize the microbe, therefore eliminating its possible spread through the body. Having a C3 deficiency in the compliment system causes frequent, severe recurrent infections."
2. Beginning with introduction of gram negative (LPS-containing) bacteria into a break in the skin, list step by step the events leading to neutrophil extravasation and attack on the bacteria. (15 points)
Christa Skow wrote this answer, which covers every important step nicely. I've added a couple of items in [] for clarification. "Once gram (-) bacteria enter the skin the LPS binds to an LPS receptor upon a macrophage. The macrophage, in turn, releases TNF (tumor necrosis factor) which signals the endothelium causing increased thickness and stickiness along with increases expression of [ICAM's with] Ig-like domains, selectins, and other receptors. The release of chemokines from the endothelial cells signals the neutrophils rolling [via selectins] along the endothelium to arrest their movement, become activated [activate their integrins], and increase their adhesion surface area. After adhesion [arrest], the neutrophil undergoes transendothelial migration in which it leaves the blood vessel in order to reach the site of infection. The TNF released by the macrophages highly activates the neutrophils, which results in [aggressive phagocytosis and] the releasing of cytotoxic substances [into phagolysosomes] which kill the bacterial cells."
Key points (a list like this would also get full credit):
Another acceptable full-credit answer was based on complement; only the parts which are different are boldface:
3. Name two cytokines produced by Th1 cells, and two produced by Th2 cells. What immune defense mechanisms are induced by Th1? By Th2? (10 points; write on the back of this sheet)
See Table 13-2, page 326, for the answer.