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.

Example input: 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.
Example output: serum
Example explanation: Serum is a substance of the organism and needs to be tagged.
Q:  Allergen and particle dose - response experiments in BALB / cA and NIH mice Levels of serum OVA - specific IgE ( A , D ) , IgG1 ( B , E ) and IgG2a ( C , F ) on day 26 after injection into one hind footpad of 100 ( open columns ) , 50 ( gray ) or 10 ( black ) mug OVA combined with 100 , 40 , 10 or 0 mug PSP , or buffer ( HBSS ( hatched ) ) , in BALB / cA ( A , B , C ) and NIH ( D , E , F ) mice .
A:
serum