In this task, you are given a sentence. You are expected to write the name of the organism substances in the body mentioned in the input. Although there might be several correct answers, you need to write one of them.
One example is below.
Q: Antisperm antibodies were assessed in the serum samples of 73 men unable to ejaculate naturally and on the sperm cells of 13 of these men.
A: serum
Rationale: Serum is a substance of the organism and needs to be tagged.
Q:  As GM1 is a major component of lipid rafts and recent studies suggest that Abeta accumulation in these lipid rafts is an early event in AD development , GM1 might play an important role in the early steps in AD pathogenesis [ 155 , 156 ] .
A:
lipid rafts