There are 25 million to a billion different T-cells in your body. Each cell has a unique T-cell receptor that can fit with only one kind of antigen, like a lock that can fit with only one shape of key. Antigens and receptors work a lot like a lock and key. Each of the 25 million to a billion different T-cells fit with a different shape of antigen.
Motivating operation. Motivating operation (MO) is a behavioristic concept introduced by Jack Michael in 1982. It is used to explain variations in the effects in the consequences of behavior. Most importantly, a MO affects how strongly the person is reinforced or punished by the consequences of their behavior.
uk â /ÉËpriË.ÊÉ.tÉªv/ us â /ÉËpriË.ÊÉ.tÌ¬Éªv/. âº showing that you understand how good something is, or are grateful for something: It's nice to have an appreciative audience. I'm very appreciative of all the support you've given me. Thesaurus: synonyms and related words.