Final answer:
T-cells recognize processed antigen plus MHC molecules which act as markers to inform T-cell that is in contact with another cell.
Step-by-step explanation:
T-cells recognize processed antigen plus MHC molecules which act as markers to inform T-cell that is in contact with another cell. These MHC molecules, also known as major histocompatibility complex molecules, are proteins that are involved in presenting processed antigens to T-cells.
The T-cell receptor (TCR) molecules on T-cells bind to the antigen-MHC complex, allowing the T-cell to recognize and respond to the antigen.