501
The salient exceptions were spleen , thymus , and red blood cells , which had almost equal numbers of cells expressing the wild - type or the recombined allele , implying that GPI - linked proteins are not essential for the derivation of these tissues .
 None
Given options, please tell me the categories of all the listed entity words.Output format is "type1: word1; type2: word2". 
Option: Disease 
Text: {0} 
 Entities:  
Answer:
 None