Local T-T cell and T-B cell interactions: a cellular automaton approach.
In this paper we use cellular automata to study growth factor (IL-2) dependent proliferation of helper T cell (Th) and B cell clones at the level of individual cells. We argue that such a spatially- and individual-oriented approach can provide important insights, not obtainable by more conventional modelling approaches in which the immune system is modelled as a well mixed collection of clones. Two questions are examined: (1) under which conditions can a cell which produces its own growth factor (i.e. Th cells) be regulated by it; and (2) if a growth factor is effective only locally, and if both Th and B cells depend on growth factors excreted by Th cells, how can the spatial segregation of T cells and B cells in lymphoid organs and/or at acute infection sites be explained? The results show that, firstly, autocrine regulation can indeed occur in two ways: it can ensure (a) that the cell reacts only on its growth factor when packed inside tissue of arbitrary cells or (b), that the cell reacts only when close to other growth factor producing cells; and secondly, segregation of T cells and B cells results automatically from simple assumptions about the interaction and proliferation of the cells, notwithstanding the fact that proliferation is slowed down by this segregation.
Hogeweg
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Bioinformatica, Padualaan, Utrecht, The Netherlands.
D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology*; D002455:Cell Division; D003198:Computer Simulation; D004058:Diffusion; D006801:Humans; D007376:Interleukin-2 / Q000378:metabolism; D008211:Lymphocyte Cooperation; D008954:Models, Biological; D013601:T-Lymphocytes / Q000276:immunology*; D006377:T-Lymphocytes, Helper-Inducer / Q000276:immunology / Q000378:metabolism
D007376:Interleukin-2