Latest Immune Models and Hybrid Approaches - Immunological Computation: Theory and Applications - page 163

cytokines by other immune cells. h ese interactions form a lymphoid endocrine system
ca lled the cy tok ine net work. h e immune cells in the cytokine network perform a dual
role, producing cytokines and carrying out the immune response (acting as eff ector
cells). h e cytokines produced by the network regulate the development and growth
of the responding immune cells.
From a computational point of view, the input in the cytokine network has the
state of disease (extent and severity) and the state of the ongoing responses (extent
and e cacy), whereas the output includes the proliferation of selected eff ector cells
and the organization of new responses.
h e model of the cytokine network proposed by Horne and van den Bergt
(2007) considered an intercellular medium in which n distinct chemical species of
cytokines diff use and are well mixed. Both the input and output are encoded by the
concentrations of the various cytokines. h e artifi cial cytokine network includes
the following elements:

Cytokine concentrations
Cytokine types
External stimuli
h e density of cell for each type

Cytokine production by a cell of any one of these types depends on external stimuli
as well as the cytokines themselves. h e system as a whole is functional, mapping
the external stimuli into a cytokine profi le. h e kinetics of the cytokine network
is divided into two types: the dynamics of the cytokines and the dynamics of the
cytokine-producing cells. h e following equation was used to calculate the dynam-
ics of the cytokines:

m

∑

i

……

k

u ψ (, , ,, ,) u u s s u

k

lk 1 n 1 r l k

l 1

where u is the cytokine concentration and s is the external stimuli. Function
ψ lk

>

0 expresses the eff ect of the cytokines and external stimuli on the produc-
tion of cytokine k by a cell of type l ; υ k

>

0 is the rate of degradation of the k th

cytokine.
h e dynamics of the cytokine-producing cells was measured by the following
equation:

i l

……

((, , ,, ,) u u s s )

l 1 n 1 r l l

l >

where 0 expresses the eff ect of the cytokines and external stimuli on the pro-

liferation rate of a cell of type l and µ l

>

0 is the death rate of cells of type l .