Passage I
Table 1 lists various components of the human immune system and some of their actions. An antigen is a foreign substance that elicits an immune response. An antibody is a molecule that binds specific antigens.
Figures 1 and 2 show the time periods during which cell and/or antibody concentrations are typically above normal during the 28 days after first exposure to an antigen.
Figure 3 shows the stages of infection in humans exposed to the human immunodeficiency virus (HIV), the virus that causes AIDS.
Table 1 and Figure 3 adapted from Neil A. Campbell, Biology, 3rd ed.
©1993 by the Benjamin/Cummings Publishing Company, Inc.
Figure 1 and 2 adapted from Peter H. Raven and George B. Johnson,
Understanding Biology. ©1988 by Times Mirror/Mosby College Publishing.
2. Blood banks screen donations for the presence of viruses by measuring the concentration of IgG antibodies. Based on Figure 2, how many days after the first exposure to a virus would the concentration of IgG antibodies be highest in the blood?
Your Answer is
Correct Answer is H
Explanation
Look at the IgG curve in the second picture of figure 2. When the abscissa is around 19-20 days, the ordinate is the largest, so the H option is consistent