20295
The result was humanized IgG2 found in rat embryo / fetal tissues as early as gestation day 11 with a > 1000 - fold increase in the amount of total IgG2 by day 21 .
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Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
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