tokens: Positive selection refers to the active process of rescuing MHC -restricted thymocytes from programmed cell death .
folded_tokens: positive selection refers to the active process of rescuing mhc -restricted thymocytes from programmed cell death .
labels: B-other_name I-other_name O O O O O O O B-protein_complex O O O B-other_name I-other_name I-other_name O