T-cell Activation & Helper T-cell Actions

How do Helper T-cells get activated?

Helper T-cells are activated when their receptors (TCRs) and a co-receptor (CD4) bind to MHC-II molecules on antigen-presenting cells (APCs) like dendritic cells or macrophages.

What is the first signal that activates Helper T-cells?

The first signal is the binding of Helper T-cell receptors (TCRs) to MHC-II molecules on an APC.

What is the second signal that activates Helper T-cells?

The second signal is the release of interleukins (IL) from the APC, which causes a positive feedback loop, helping the Helper T-cell become fully active.

What do activated Helper T-cells do?

Activated Helper T-cells attract macrophages, neutrophils, and NK cells to help fight infections. They also stimulate other T-cells and B-cells to multiply and fight the infection.

How do Cytotoxic T-cells get activated?

Cytotoxic T-cells get activated when their TCRs and co-receptors (CD8) bind to MHC-I molecules on infected cells.

What is the first signal that activates Cytotoxic T-cells?

The first signal is the binding of Cytotoxic T-cell receptors (TCRs) to MHC-I molecules on infected cells.

What is the second signal that activates Cytotoxic T-cells?

The second signal comes from interleukins (IL) released by Helper T-cells, which helps activate the Cytotoxic T-cells.