Memory cell

Part of these T-lymphocytes transform into memory cells. These cells are different from their ancestors in that they are activated by a much lower antigen binding strength and also much less depend on signal 2. Now self-antigens can activate these T-lymphocytes. As during activation continuously new memory cells are formed, autoreactivity is sustained and autoimmune disease follows (Fig. 2). 

These are supplied by the secretion of peptide molecules (termed cytokines or lymphokines) fiom a subset of the T-cell family (the helper T cells, TH cells). These peptide molecules (interleukins (IL) 2,4,5 and 6) stimulate the B cells to proliferate, undergo clonal expansion and mature into plasma cells which secrete antibody and also into the longer-hving, non-dividing memory cells. 

The ideal of any vaccine is to provide life-long protection to the individual against disease. Immunological memory (Chapter 14) depends upon the survival of cloned populations of small B and T lymphocytes (memory cells). These small lymphocytes have a lifespan in the body of ca. 15-20 years. Thus, if the immune system is not boosted, either by natural exposure to the organism or by re-immunization, then immunity gained in childhood will be attenuated or lost completely by the age of 30. Those vaccines which provide only poor protection against disease have proportionately reduced time-spans of effectiveness. Yellow fever vaccination, which is highly effective, must therefore be repeated at 10-year intervals, whilst typhoid vaccines are only effective for 1-3 years. Whether or not immunization in childhood is boosted at adolescence or in adult life depends on the relative risks associated with the infection as a function of age. 

Forster R, Emrich T, Kremmer E, Lipp M. Expression of the G-protein-coupled receptor BLR1 defines mature, recirculating B cells and a subset of T-helper memory cells. Blood 1994 84 830-40. 

Early Memory Cells That Display an Effector Phenotype... 

Early memory cells CXCR3, CCR4 Used to identify these cells, which have an otherwise naive phenotype... 

Wu CY, Kirman JR, Rotte MJ, et al. Distinct lineages of T(H)1 cells have differential capacities for memory cell generation in vivo. Nat Immunol 2002 3 852-858. 

Baekkevold ES, Wurbel MA, Kivisakk P, et al. A role for CCR4 in development of mature circulating cutaneous T helper memory cell populations. J Exp Med 2005 201 1045-1051. 

Sutton, M. A., and Schuman, E. M. (2006). Dendritic protein synthesis, synaptic plasticity, and memory. Cell 127, 49-58. 

In an immune response, antibodies are produced and secreted by the B-lymphocytes in conjunction with the T, cells. In the majority of hapten-carrier systems, the B cells end up producing antibodies that are specific for both the hapten and the carrier. In these cases, the T lymphocytes will have specific-binding domains on the carrier, but will not recognize the hapten alone. In a kind of synergism, the B- and T-cells cooperate to induce a hapten-specific antibody response. After such an immune response has taken place, if the host is subsequently challenged with only the hapten, usually it will respond by producing hapten-specific antibodies from memory cells formed after the initial immunization. For a review of immunobiology (see Janeway, 2004). 

Ami S, Joachim C (2001) Logic gates and memory cells based on single C60 electromechanical transistor. Nanotechnology 12 44... 

Lee, H. Kim, Y. K. Kim, D. Kang, D.-H. 2005. Switching behavior of indium selenide-based phase-change memory cell. IEEE Trans. Magnetics. 41 1034-1036. 

Reed, M. A. Chen, J. Rawlett, A. M. Price, D. W. Tour, J. M. 2001. Molecular random access memory cell. Appl. Phys. Lett. 78 3735-3737. 

Tsien, I. Z., Huerta, P. T. and Tonegawa, S. The essential role of hippocampal CA1 NMDA receptor-dependent synaptic plasticity in spatial memory. Cell 87 1327-1338,1996. 

Figure 1.7. Lymphocyte activation. When naive lymphocytes first encounter the antigen that is recognised by their receptor, they are stimulated to differentiate and proliferate. This clonal expansion is aided by the production of cytokines. Two cell types develop from this process the effector cells (i.e. either antibody-secreting plasma cells or cytotoxic T cells) and memory cells. Both cell types possess virtually the same receptor that was expressed on the naive lymphocyte.

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