280
Therefore, we examined the RB status of a series of B-cell mutants that are defective in class II expression, generated either in vitro or derived from Bare Lymphocyte Syndrome (BLS) patients.
 RB
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: cell line, protein, RNA, DNA, cell type 
Text: {0} 
Answer:
 RB