**5.1 T-cells**

T-cell is divided into "helper T cell (Th)", "cytotoxic T cell (Tc)", "natural killer T cell (NKT)" and "memory T cell (Tm)" [66]. Th cells are responsible for activation and proliferation of cytokines. They also assist in the maturation of B cells and activation of Tc and macrophages [66]. Helper T cell is divided into Type 1 (Th1) and Type 2 (Th2) T-helper cells [66]. Cell-mediated response is usually aided by Th1. Resulting in the recruitment of macrophages to an infected site for action [66]. Interferon gamma (IFNγ) and macrophages are the main effector biomarkers of Th1 immune response [66]. Th1 response is usually mounted against intracellular bacteria and protozoa [66]. Th2 on the other hand aids in the activation and proliferation of B cells, and is a component of humoral immunity [66]. Th2 cells functions to clear extracellular bacteria from the body [66]. Eosinophils basophils, and mast cells are important effector agents of Th2 immune response [66]. Cytotoxic T cell (Tc) is responsible for the disruption and cytolysis of host cells infected by virus [66]. They also play key role in tumour and cancer immunity [66]. Natural killer T cell (NKT) also assist in B cell activation and microbial defence [66].
