CD3 (Cluster of differentiation 3), originally known as T3, is one of the first groups of human T lymphocyte surface antigens recognized by monoclonal antibodies. It has been reported that antibodies against CD3 could either stimulate T cells to divide or inhibit the progress of effector functions according to the conditions used. It plays an important role in T cell and the CD3 T-cell co-receptor helps to activate the cytotoxic T-Cell and T helper cells. The CD3 molecule is composed of a protein complex and consists of four distinct chains. The complex of mammals contains a CD3γ chain, a CD3δ chain, and two CD3ε chains. All these chains associate with T-cell receptor and the ζ-chain to generate an activation signal in T lymphocytes. Gp120 (GP120, Envelope glycoprotein 120) is a glycoprotein exposed on the surface of the human immunodeficiency virus (HIV) envelope, that is part of the outer layer of this virus. The 120 in the name represents its molecular weight of 120 kDa. The gp120 is encoded by the HIV env gene, which is approximately 2.5 kb long and codes for 850 amino acids. The primary env product is the protein gp160, which is cleaved to gp120 and gp41 in the endoplasmatic reticulum. It presents as viral membrane spikes containing three molecules of gp120 bound together and anchored to the membrane via gp41 protein, involved in virus-cell attachment. Gp120 is essential for the viral infection because it promotes the HIV entry into the host cells and that is why it is best-known and most researched in HIV infection.