Final answer:
Memory CD8 T cells are long-lived immune cells that persist after an infection and can rapidly respond upon re-exposure to the same pathogen. They contrast with effector T cells, which die after the pathogen is cleared. Memory T cell exhaustion can lead to decreased immune response and increased susceptibility to diseases such as HIV/AIDS.
Step-by-step explanation:
Exhaustion of Memory CD8 T CellsMemory T cells are a subset of T lymphocytes that play a critical role in the immune response to pathogens. After the clearance of an infection, cytotoxic T cells, which are capable of destroying infected cells and the viruses they contain, mostly die off. In contrast, a portion of these cells remain as long-lived memory cells, poised to respond swiftly to future exposures to the same pathogen. These memory cells can rapidly proliferate and produce many cytotoxic T cells that are specific to an antigen, upon re-exposure to the same pathogen, enhancing the body’s immune defense.
MHC class I molecules, which are found on the surface of almost all body cells, bind to the CD8 molecule on T cells. This interaction is necessary for the proper functioning of CD8+ cytotoxic T cells. It is important to note that a decrease in helper T cells, especially CD4+ T cells, can lead to immune deficiencies, as seen in diseases such as HIV/AIDS. An HIV infection can lead to a severe reduction in CD4+ T cells, impairing adaptive immune functions and making the body vulnerable to opportunistic infections.
Furthermore, acute restraint stress has been shown to increase the numbers of memory and effector helper T cells, which may contribute to the heightened immune response upon antigen re-exposure. The memory cells, unlike effector cells, do not respond during the primary immune response but can become effector cells quickly upon re-exposure to the antigen. In contrast to effector cells, which undergo apoptosis after the infection subsides, memory cells persist in the circulation, retaining the immunological memory of the pathogen.