Figure 2

Effect of central and peripheral tolerance on immune self-reactivity. The x-axis represents the effective abundance of a self-Ag, in arbitrary units. Top: probability that self-reactive lymphocytes towards a given self-Ag remain after the induction of central tolerance. The curve corresponds to 1 – f _i from eqn. 1 and it can be also interpreted as the fraction of self-Ags with a given effective abundance that remain untolerated. Middle: probability that an Ag (self or non-self) is efficiently presented by an APC. Bottom: combined effect of central and peripheral tolerance on the probability of targeting a self-Ag. In our simple model, peripheral tolerance is determined by the threshold a ^*, the minimum effective abundance required for efficient Ag presentation. In the absence of peripheral tolerance, the probability of targeting a self-Ag becomes greatest for those self-antigens with effective abundances close to a ^max.