Final answer:
Cytotoxic T cells (CTLs) are activated in secondary lymphoid tissues by antigen-presenting cells (APCs) through antigen recognition and subsequent interactions involving MHC I and the CD8 co-receptor.
Step-by-step explanation:
Activation of Cytotoxic T Cells
Cytotoxic T cells, also known as cytotoxic T lymphocytes or CTLs, become activated through a multistep process involving antigen-presenting cells (APCs). Initially, these T cells are activated by antigen recognition in secondary lymphoid tissues. Antigen-presenting cells, such as macrophages, dendritic cells, and B cells, present antigens on their surface with Major Histocompatibility Complex Class I (MHC I) proteins. CTLs recognize these antigens using their T-cell receptors (TCRs) and co-receptor CD8, leading to their activation.
A correct match for the activation process is: a) Antigen recognition / peripheral lymphoid. This process involves the CTLs recognizing the foreign antigen presented by an APC and receiving additional signals, which may include cytokines released by the APC and helper T cells. Through this interaction, CTLs are stimulated to proliferate and differentiate into effector cells that can target and destroy cells infected with pathogens or memory cells that provide long-term immunity.