How do you activate T cells?

T-cells are the primary offensive force against antigens threatening the body, and are activated by two separate signals. If only one signal is received, the T-cells will not fully respond, which is how and why the immune system does not fully rouse against every possible threat. This is termed ‘peripheral tolerance’. Every T cell is specialized to respond to a specific threat, forming an efficient system that allows for a wide recognition of possible antigens, without overburdening any one cell.

The two signals that are necessary are:

1. Binding of the specialized T cell receptor (often abbreviated as TCR) to its target peptide.
2. The antigen engaging with the biomolecules CD80 or CD86, or with cytokines.

If both signals are received, the T-cells will fully activate against the threat by proliferating, providing assistance for B cells, and otherwise assisting in the development of the adaptive immune response that ensures a consistently-defended system.

In the laboratory, T cell activation is typically measured by cell assays with known concentrations of antigens and immune cells incubated for set lengths of time. Microplates are the typical format, but many variations exist depending on the scale and nature of the experiment. 

References:

1. Ralph C.Budd, Karen A.Fortner (2017) Kelley and Firestein's Textbook of Rheumatology (Tenth Edition) Volume 1 Pages 189-206 https://doi.org/10.1016/B978-0-323-31696-5.00012-7.
2. Tak W. Mak, Mary E. Saunders (2006) The Immune Response. Pages 373-401 https://doi.org/10.1016/B978-012088451-3.50016-8.