SWARTHMORE PHYS 120 - Complexity and the Immune System

Unformatted text preview:

Complexity and the Immune SystemWhy look at the immune system?Main IssuesImmune System BasicsNiels Kaj Jerne Danish ImmunologistSelf Defense in a Network SystemNetworks that do thisPowerPoint PresentationSlide 9ResultsBut do we really need the network?What about self-recognition?Can networks do this?But… the non-network solutionBut, immune networks have other applications!ReferencesComplexity and the Immune SystemWhy look at the immune system?-Intermediate level-One of the major information processing systems in the body (with neural system)-Competing theories that can be tested - we’ll see how well the network theory holds up in this caseMain Issues•Protection: find and destroy invaders•Self Recognition: don’t destroy cells from your own body•Memory of past pathogensImmune System Basics•Antigens and antigen determinants•Multiple epitopes per cell of any type•Antibodies (4 chains; “variable region”)•B cells and clones•T cells (recognize peptide fragments from MHC)Niels Kaj JerneDanish Immunologist•Shared the Nobel prize in 1984 for his work•Theory of antibody formation (from genetic variation rather than a response to pathogens) - 1955•The body learns to distinguish between self and nonself in the thymus - 1971•Concept of the immune system as complex, self-regulating network - 1974Self Defense in a Network System•Key factors:–Quick and full response from those antibodies that can bind to the right antigen determinants– Response that dies down (ie doesn’t explode)–Memory of past pathogens so that response is quicker next timeNetworks that do this•Coupled PDEs involving the concentration of antibodies and antigens•Multi-dimensional space that maps shape characteristics that allow binding (eg hydrophilicity/polarity, physical shape, etc)•Cellular automata where each point r (vector) is coupled to the points around its mirror image, -rResults-This behavior was seen for a region near the boundary between stable and chaotic behavior of the automata-Preserved over a range of dimensions (biologically need at least 5 dimensions to cover “shape space”) and lattice sizesBut do we really need the network?•Genetic variation can lead to B and T cells that cover the entire range of pathogens, and each antibody hits on average one antigen•B cells differentiate into memory cells, which are able to quickly split into lots of effector cells and more memory cells•After an attack, have more memory cells, and they’re more coordinatedWhat about self-recognition?-Self recognition is “learned” - each organism has different self-antigens and can recognize them-If “other” antigens are introduced at a particular stage in development, the organism will incorporate them as “self” (mice)Can networks do this?•Yes! Well, small networks can. Particularly, networks with an odd number of nodes connected in loops can. •Some networks blow up under a small but constant antigen concentration•But some don’t - and those are the ones that seem to correspond most closely to biological realityBut… the non-network solution•T cells are “weeded out” in the thymus if they attack the self antigens•B and T cells somehow trigger a self-destruction signal if they respond too strongly or too weakly to self antigens as they developBut, immune networks have other applications!•Data analysis•Other computers•Models for body-wide immune events (as models of system-wide behavior, can explain some medical results)References•Bernandes, A. T. et al. Immune network at the edge of chaos. Journal of Theoretical Biology. ISI Web of Knowledge. 1997. •Calenbuhr, V. et al. Natural tolerance in a simple immune network. Journal of Theoretical Biology. ISI Web of Knowledge. 2001. •Sun, J. et al. Glassy dynamics in the adaptive immune response prevents autoimmune disease. Physical Review Letters. ISI Web of Knowledge. 2005. •Sadava, David, et al. Life: The Science of Biology. 2006. Chapter 18: The Immune System.•Muc-Wierzgon, M, et al. On the holistic approach in cancer biology: Tumer necrosis factor, colon cancer cells, chaos theory and complexity. Journal of Biological Regulators and Homeostatic Agents. ISI Web of Knowledge. 2004. •"Jerne, Niels K.." Encyclopædia Britannica. 2008. Encyclopædia Britannica Online. 3 May 2008


View Full Document

SWARTHMORE PHYS 120 - Complexity and the Immune System

Documents in this Course
Load more
Download Complexity and the Immune System
Our administrator received your request to download this document. We will send you the file to your email shortly.
Loading Unlocking...
Login

Join to view Complexity and the Immune System and access 3M+ class-specific study document.

or
We will never post anything without your permission.
Don't have an account?
Sign Up

Join to view Complexity and the Immune System 2 2 and access 3M+ class-specific study document.

or

By creating an account you agree to our Privacy Policy and Terms Of Use

Already a member?