instruction:
Given scientific fact as input, generate the question from this fact such that it can be answered from the input.
question:
Most protein antigens require signals from helper t cells (th2) to proceed to make antibody.
answer:
Most protein antigens require signals from helper t cells (th2) to proceed to make what?

question:
Multiple genes mutations is usually necessary to develop cancer.
answer:
What is usually necessary to develop cancer?

question:
Calcium ion is an example of a second messenger.
answer:
Calcium ion is an example of what kind of messenger?