The term ZBA (Zero Balance Account) is sometimes used to describe a transit account. In reality, ZBAs are a completely different story and are usually used in an acquiring and merchant account context, where one party opens the account and another sweeps (clears) it daily.
Helper T cells are the major driving force and the main regulators of the immune defense. Their primary task is to activate B cells and killer T cells. However, the helper T cells themselves must be activated.
It is made up of three layers of cells: the supporting cells, the olfactory receptor cells, and the basal cells. Supporting cells are similar to glial cells and help produce mucus. Basal cells are the source of new receptors.