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.
Epithelial cells help to protect or enclose organs. Most produce mucus or other secretions. Certain types of epithelial cells have tiny hairs called cilia, which help remove foreign substances. Epithelial cells are arranged in single, or multiple layers, depending on the organ and location.