Immune system consists of regular or nonspecific mechanisms for the defense of an separate against foreign antigens \ These natural defense are present from birth and do not necessarily require exposure to antigens for their development. Natural defense, the body’s first line of defense , consist of both anatomic and chemical barriers to microbial invasion. In a healthy adult person, approximately 10-10 new blood cells are produced daily in order to maintain steady state levels in the peripheral circulation in all cellular blood components are derived from hematopoietic stem cells  Adaptive immune system does not retrieve long-lasting or protective immunity to the host. Innate immune systems supply immediate defense against infection, and are found in all classes of plant and animal life. The innate immune system comprises the cells and mechanism that protect the host from infection by other organisms in a nonspecific manner.

T cells belong to a group of white blood cells (WBC) known as lymphocytes, and play a central role in cell-mediated immunity  WBC can be renowned from other lymphocyte types, such as B cells and natural killer cells (NK cells) by the presence of a special receptor on their cell surface called T cell receptors (TCR). The contraction T in T cell, stands for thymus, since this is the principal organ liable for the T cell’s maturation. Different subsets of T cells have been revealed, each with a different function . Epitope is confined to a small region on the surface of an antigen that is capable of eliciting an immune response and a portion of a molecule to which an antibody binds