Nikolas
Created page with "While B-cells can bind free antigens in the blood and tissues, T-cell receptors can only bind to antigens that are being presented to them by other cells. This means that a T-cell cannot recognize a bacterium or virus floating past; some other cell has to digest the bacterium or virus and then ''present'' a small part of it, an antigen, from the pathogen to the T-cell for it to be activated. == Major histocompatibility complex == A protein called major histocompatibilit..."
