Scale Invariance of Immune System Response Rates and Times: Perspectives on Immune System Architecture and Implications for Artificial Immune Systems

摘要

Most biological rates and times decrease systematically with organism bodysize. We use an ordinary differential equation (ODE) model of West Nile Virusin birds to show that pathogen replication rates decline with host body size,but natural immune system (NIS) response rates do not change systematicallywith body size. This is surprising since the NIS has to search for smallquantities of pathogens through larger physical spaces in larger organisms, andalso respond by producing larger absolute quantities of antibody in largerorganisms. We call this scale-invariant detection and response. We hypothesizethat the NIS has evolved an architecture to efficiently neutralize pathogens.We investigate a range of architectures using an Agent Based Model (ABM). Wefind that a sub-modular NIS architecture, in which lymph node number and sizeboth increase sublinearly with body size, efficiently balances the tradeoffbetween local pathogen detection and global response using antibodies. Thisleads to nearly scale-invariant detection and response, consistent withexperimental data. Similar to the NIS, physical space and resources are alsoimportant constraints on Artificial Immune Systems (AIS), especiallydistributed systems applications used to connect low-powered sensors usingshort-range wireless communication. We show that AIS problems, like distributedrobot control, will also require a sub-modular architecture to efficientlybalance the tradeoff between local search for a solution and global response orproliferation of the solution between different components. This research haswide applicability in other distributed systems AIS applications.