In the article by Fung-Lung and colleagues, it was found that CD8 is a crucial molecule for the development of cytotoxic T cells. They skillfully presented the implications of their results and convincingly concluded the importance of CD8 in the immune response. Through the use of knockout mice, Fung-Lung et al. were able to demonstrate that disruption of the CD8α gene impairs the cytotoxic functions of T lymphocytes and does not affect the functions of helper T lymphocytes. CD8 has been and still is widely studied in immunological diseases, particularly leukemia. Various studies show that CD8 plays an important role in the effects and development of specific types of leukemia. Background CD8 is an important co-receptor molecule for the activation of T lymphocytes, present on many cells of the lymphoid system and exists in 2 forms; the homodimeric αα and heterodimeric αβ form. The αα homodimer is found on natural killer cells, γδ T cells, intestinal lymphocytes, and some dendritic subsets. The function of the αα homodimer has not yet been clearly identified. The αβ heterodimeric form is found on approximately 90% of killer T cells and plays a major role in enhancing T cell activation by increasing their sensitivity to antigens. It also stabilizes the interaction between the TCR and the MHC class I molecule. (Cole et al., 2012) CD8 has two subunits; α and β, both of which contain an NH2-terminal domain and a “hinge” region, which connects the NH2-terminal to the membrane-spanning region. The NH2 terminal is similar to the variable domains of immunoglobulins and contains 9 beta strands divided into 2 beta sheets. A disulfide bridge connects strand B and support F of the CD8α subunit. There is also an interleaf connection between strands B and C, suggesting that either...... middle of paper......ritish Journal of Haematology. (First view). National Center for Biotechnology Information. (2014). CD8A molecule. National Center for Biotechnology Information. (2014). CD8B molecule. Shore, DA, Issafras, H., Landais, E., Teyton, L., Wilson, IA (2008). The crystal structure of CD8 in complex with YTS156.7.7 Fab and the interaction with other CD8 antibodies defines the mode of binding of CD8αβ to MHC class I. Journal of Molecular Biology, 384(5), 1190-1202.te Raa, GD, Pascutti, MF, Garcia-Vallejo, JJ, Reinen, E., Remmerswaal, EBM, ten Berge, IJM, van Lier, RAW, Eldering, E., van Oers, MHJ, Tonino, SH, Kater, AP (2013). CMV-specific CD8+ T cell function is not impaired in chronic lymphocytic leukemia. Blood, 123(5), 717-724. Zhang, N. and Bevan, M.J. (2011). CD8+ T cells: foot soldiers of the immune system. Immunity, 35(2), 161-168.