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Free keywords:
idiotypic network; self-tolerance; control of autoreactive idiotypes; autoimmunity; bitstring model; mean-field theory
Abstract:
We consider the problem of self-tolerance in the frame of a minimalistic model of the idiotypic
network. A node of this network represents a population of B-lymphocytes of the
same idiotype, which is encoded by a bit string. The links of the network connect nodes
with (nearly) complementary strings. The population of a node survives if the number of
occupied neighbors is not too small and not too large. There is an influx of lymphocytes
with random idiotype from the bone marrow. Previous investigations have shown that this
system evolves toward highly organized architectures, where the nodes can be classified
into groups according to their statistical properties.The building principles of these architectures
can be analytically described and the statistical results of simulations agree very well
with results of a modular mean-field theory. In this paper, we present simulation results
for the case that one or several nodes, playing the role of self, are permanently occupied.
These self nodes influence their linked neighbors, the autoreactive clones, but are themselves
not affected by idiotypic interactions. We observe that the group structure of the
architecture is very similar to the case without self antigen, but organized such that the
neighbors of the self are only weakly occupied, thus providing self-tolerance.We also treat
this situation in mean-field theory, which give results in good agreement with data from
simulation. The model supports the view that autoreactive clones, which naturally occur
also in healthy organisms are controlled by anti-idiotypic interactions, and could be helpful
to understand network aspects of autoimmune disorders.
