The term is "Central Tolerance". The Thymus (Which someone else mentioned) effectively checks the following: (1) Does the cell react to an antigen (Foreign pa

The term is "Central Tolerance". The Thymus (Which someone else mentioned) effectively checks the following: (1) Does the cell react to an antigen (Foreign particle) [β-selection] (2) Does the cell still work with the immune system (Can it bind to the cells it needs to bind to once it finds the antigen) [Positive Selection] (3) Does the cell recognize only foreign particles and not the body itself [Central Tolerance / Negative Selection]