Antibodies to Trypanosoma Glycoprotein Variants Over Time
Sleeping sickness is caused by the unicellutar Trypanosoma parasite. The surface of this parasite is covered by glycoproteins that are encoded by a gene with more than 1,000 duplications in the trypanosome genome. Each of the gene copies is slightly different and has different molecular structures. The data below show the number of parasites over time (A) and the relative amount of antibodies specific to two trypanosome glycoproteins (B) over 24 days of a human infection, and the index varies from no antibodies (0) to many antibodies (1)
Part A: Data from a Study of Parasite Levels
Day
4
6
8
10
12
14
16
18
20
22
24
Number of Parasites (in millions) per mL of Blood
0.3
0.2
0.2
0.7
0.2
0.1
1.2
0.9
1.2
0.6
0.1
Part B: Data from a Study of Antibody Levels
Day
4
Antibody Specific to Glycoprotein Variant A
0
6
0
8
0.2
10
0.5
12
1
14
1
16
1
18
1
20
1
22
1
Antibody Specific to Glycoprotein Variant B
0
0
0
0
0
0.1
0.3
0.9
1
1
24
1
1
Use the passage to answer the question.
The data in part B of the passage show antibody levels to two of the trypanosome glycoproteins over time. However, the data in part A show that, on day 20, the parasite load increases again before decreasing on day 24, even though the antibody levels for both variants A and B were high. Write a paragraph in which you draw conclusions trypanosome biology and the adaptive immune system could have produced this sudden increase about how