What are the three classes of lymphocytes, and where does each class originate?

Skin tests are used to determine if a person 

(a) Has an active infection

(b) Has been exposed to a particular antigen

(c) Carries a particular antigen

(d) Has measles

(e) Can produce antibodies

While walking along the street, you and your friend see an elderly woman whose left arm appears to be swollen to several times its normal size. Your friend wonders aloud what might be its cause. You say that it may be likely that the woman had a radical mastectomy (the removal of a breast because of cancer). Explain the rationale behind your answer.

Willy is allergic to ragweed pollen and tells you that he read about a medication that can help his condition by blocking certain antibodies. Do you think that this treatment could help Willy? Explain.

Which of the following conditions may lead to the development of autoimmunity?

a. Self antigens not previously encountered by T cells are released into the circulation

b. Foreign antigens mimic self antigens

c. Cells may inappropriately display class II MHC molecules

d. Certain pathogens nonspecifically activate B cells

e. All of the above are correct

A decrease in which population of lymphocytes would impair all aspects of an immune response?

(a) Cytotoxic T cells

(b) Helper T cells

(c) Regulatory T cells

(d) B cells

(e) Plasma cells

Perforins are proteins associated with the activity of

(a) T cells

(b) B cells

(c) NK cells

(d) Plasma cells

Where do T cells undergo central tolerance selection?

What is immunological tolerance?