RT Book, Section A1 Nguyen, Linh T. A1 Lind, Evan F. A1 Ohashi, Pamela S. A2 Tannock, Ian F. A2 Hill, Richard P. A2 Bristow, Robert G. A2 Harrington, Lea SR Print(0) ID 1127473784 T1 The Immune System and Immunotherapy T2 The Basic Science of Oncology, 5e YR 2016 FD 2016 PB McGraw-Hill Education Medical PP New York, NY SN 9780071745208 LK hemonc.mhmedical.com/content.aspx?aid=1127473784 RD 2024/10/04 AB One feature that is common to all organisms is the ability to defend themselves against challenges in the environment in which they live. Mammals have a complex phalanx of defenses against bacteria, viruses, and parasites, which comprise the immune system. The immune system can be very broadly characterized as having 2 major arms: innate immunity and adaptive immunity. The innate immune system is the "first line of defense" against pathogens, and includes macrophages and dendritic cells that function in part to present antigens to the cells in the adaptive immune system. The adaptive arm of the immune system is mediated by lymphocytes and responds with higher specificity to pathogens. Key cells of the adaptive immune system are helper T cells (Th) that express a marker known as CD4, cytotoxic T lymphocytes (CTL) that are distinguished by the CD8 marker, and B cells that produce antibodies. The molecular components of pathogens that are recognized by T and B cells are broadly referred to as antigens.