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.
CD4+ cells recognize antigen presented in the context of class II major histocompatibility complex (MHC), while CD8+ cells recognize antigen presented in the context of class I MHC. CD4+ T helper subsets include T helper type 1 (Th1), T helper type 2 (Th2), and T helper type 17 (Th17) cells (figure 1 and table 1) [1]. There is evidence that each of these subsets is involved in the defense against a certain subset of micro-organisms.