Immunology as a Metaphor for Computational ... - Napier University

Chapter 2. Background 17Antigene 0p 1e1p 2e 2p ne nFigure 2.4: Formation of a cycle allowing antigen with epitope e 0 to be remembered.The arrows denote recognition via the matching algorithmpattern recognition system, its primary intention being to learn more about the internaloperation of the immune system in real systems. However, they note “...generalisedversions of the model may be capable of performing artificial intelligence tasks”.Gibert and Routen [Gibert and Routen, 1994] adopted this approach and attemptedto apply it to create a content-addressable auto-associative memory. Inputs to theirsystem are black and white pictures of 64x64 pixels which are analogous to antigens.The aim was to present the antigen to the system, initiate a response during which amemory of the antigen would be created, then observe the existence of the memory byinitiating a secondary response via injection of the same or similar antigen. However,they report that they were unable to satisfy the simultaneous requirements of rememberingpatterns whilst maintaining system stability. They suggest two variations of themodel. In the first, they attempted to forcibly create recognition loops in the networkto enable the maintenance by the network of clones responding to the antigen, and thusprovide a memory of the antigen. However, they show subsequently that this provesunstable, in that clones would proliferate continuously and lead to collapse of the system.They modified this system to increase suppression of clones, which resulted in astable system, in which memory cells were maintained by the network but tended todissipate slowly and eventually disappear. However, the system responded poorly, inthat it did not show good quality output, particularly after a secondary response.2.2.1 Negative Selection Based ModelsA whole class of implementations of artificial immune systems focus on modellingthe generally accepted self/non-self discrimination ability of the biological immune