Fabio Luciani

Stochastic Approach in the modelling of IS

Fabio Luciani

The first model is a stochastic dynamic system for the CD8+ T naive lymphocytes (CD8+ CD95-) dynamics on the long time scale of the human life span. The purpose is to test the recent hypothesis that the depletion of virgin CD8+ T lymphocytes can be considered a likely marker of mortality. The model is capable of fitting the experimental data concerning the changes of virgin T cell concentration over age, and at the same time to reproduce survival curves similar to the demographic ones. It confirms the finite probability of having individuals with a life span much longer than the average (centenarians) and that the stochastic process is responsible of the peculiar shape of survival curves, strikingly similar from worms to humans and in outbred and inbred populations (see figure 1). The second model emphasizes the role of chronic antigenic stimuli in the clonal expansion of T and B cells over a long time scale and their role on the Immunosenescence. This is particularly relevant since the study of the chronic stimulations is quite neglected even if they are fundamental for the vaccine effectiveness.


Figure 1
Figure 1: Distribution of v(t) and survival curves
Top: Black Central curve is v(t), blue external curves v(t)±σ(t) with
v=-0.4 ; γ=0.1 (right)
v=-0.4 ; γ=0.15 (left).
Bottom: Corresponding survival curves for different values of the parameters v , γ.


Figure 2
Figure 2: Theoretical curves with demographic data represented by dots (top). Human Male (top left) and Human Females (top right). The same demographic data (down) 1994.




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