Self-study
Multiple sclerosis is an autoimmune disease: white blood cells attack the myelin sheath that protects nerve fibers in the spinal cord and brain. ███████ ███████ ███ ███ █ ████ ████ ███ ██ ████ ██ ████████████ █████ ████████ ██████████ ███ ███ ████ ████ ███ ███████ ███████████ ██ ████ ████ ███ ██████ ████████████████ ██████████ ████ ██████████ ████████ ███████ ██████████████ ██ ████████ █████████ █████ ██ █████████ ██ ███████ █████ ███████████ ██ ██ ████ ████ █████ ███████ █████ ███████████ ███ ██ ███ ██████ ███ █████████ ████████ ██ █████ ███████ ███ ███ ████████ █████████ ████████ ██████ ██████ ████████████ ██████ ███ █████ ████ ██████ ██ ██ ███████████ ████████
Summary
Scientists thought multiple sclerosis (MS) was caused by viral infections. To test this hypothesis, they used gamma interferon—a tool the body uses to combat viral infections—to treat MS. This experiment, however, resulted in the MS patients’ conditions worsening.
Notable Valid Inferences
Gamma interferon makes MS worse.
22.
Which one of the following ██ █████ ██████████ ████ ███ ███████ ██ ███ █████ ██████████ ███████████
a
Gamma interferon stops █████ █████ █████ ████ █████████ █████████████████ ██████████
This is not compatible with the experiment’s results. If gamma interferon does what (A) claims, it would interfere with the mechanism that makes MS so destructive. This would likely improve MS patients’ conditions—this contradicts the experiment, which shows the opposite effect.
b
Administering gamma interferon ██ █████ ███████ ████████ █████████ ██████ ██ ████████ ██ ███ ██████ ██ █████ █████ ██████
This could be true and may explain why gamma interferon makes MS patients’ conditions worse. By causing an increase in white blood cells, gamma interferon could increase the number of cells attacking the myelin sheath in MS patients.
c
Medical researchers have ██████████ ████ ███ █████ ██████████ █████ ██ ███ █████████████ █████ ██████████ ████ ██████ ███ ██████ ████████ █████████ ████████
This could be true and may explain why gamma interferon makes MS patients’ conditions worse. It suggests an association between increased gamma interferon levels and MS attacks.
d
It has now ████ ███████████ ████ ████ ████████ █████████ █████████ ██ ███ ████ ███████ █████ ███████████
This could be true. It suggests that scientists’ initial belief that MS is triggered by viral infections is incorrect. This could explain why gamma interferon, one of the body’s antiviral tools, is ineffective against it.
e
The drug now ████ ██ █████ ████████ █████████ ██ █████ ██ ███████ ███ ████████ ██ █████ ███████████
This could be true and may explain why gamma interferon makes MS patients’ conditions worse. It suggests that inhibiting gamma interferon levels improves patients’ conditions—this is consistent with the finding that increasing gamma interferon levels worsens patients’ conditions.