Question

What initiates T cell activation?

a)T cell activation begins with a dendritic cell processing and displaying antigen fragments on its MHC molecules.
b)T cell activation begins when the T cell differentiates into effector cells and memory cells.
c)T cell activation begins when a T cell is ingested by a macrophage.
d) T cell activation begins with the interaction of the T cell with other molecules on the cells called co-stimulators.

Answer 1

T cell activation is initiated when an APC, such as a dendritic cell or macrophage, processes and displays antigen fragments on MHC molecules, which then interact with T cell receptors on T cells.

Step-by-step explanation:

T cell activation begins with a sequence of events involving the recognition of an antigen. This process is initiated when antigen-presenting cells (APCs), such as dendritic cells or macrophages, process and present antigenic fragments on their surface through molecules called the Major Histocompatibility Complex (MHC). The correct initiation of T cell activation comes from the interaction between a T cell and an APC, where the APC has processed and displayed an antigen on its MHC molecules.

For helper T cells, activation requires the recognition of antigens presented with MHC II, while cytotoxic T cells are activated by antigens associated with MHC I. Both processes involve T cell receptors (TCRs) recognizing the specific foreign epitopes, co-receptors CD4 or CD8 interacting with MHC, and cytokine signalling that leads to activation, proliferation, and differentiation into effector and memory cells.