B2 [ U ] a situation in which people are peaceful and agree with each other, or when things seem right or suitable together: racial harmony (= good feelings between different races) domestic harmony (= good feelings in the family or home) Imagine a society in which everyone lived together in (perfect) harmony. We must ensure that tourism develops in harmony with the environment.
Once activated, helper T cells start to divide and to produce proteins that activate B and T cells as well as other immune cells. The killer T cell is specialized in attacking cells of the body infected by viruses and sometimes also by bacteria. It can also attack cancer cells. The killer T cell has receptors that are used to search each cell that it meets.
T cells are activated when a particular phagocyte known as an antigen-presenting cell (APC) displays the antigen to which the T cell is specific. This blended cell (mostly human but displaying an antigen to the T cell) is a trigger for the various elements of the specific immune response. A subtype of T cell known as a T helper cell performs a number of roles. T helper cells release chemicals to.