# Cells' consumption of cytokine concentration

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### Victoria Ponce

Oct 2, 2019, 4:34:03 AM10/2/19
to Morpheus users
Hello all,

I am trying to integrate in my ABM the consumption of cytokines by  cells and I am having some trouble doing it and I hope you can help.

A cell can sense and consume the cytokine concentration using a Mapper as in https://morpheus.gitlab.io/blog/2018/02/13/a-multiscale-mini-model/
However how can I decrease the concentration of the cytokine after the cell has consumed it?

Best,

Victoria

### Walter de Back

Oct 2, 2019, 5:22:26 AM10/2/19
to Victoria Ponce, Morpheus users
Hi Victoria and welcome to the forum,

A cell can sense and consume the cytokine concentration using a Mapper as in https://morpheus.gitlab.io/blog/2018/02/13/a-multiscale-mini-model/
However how can I decrease the concentration of the cytokine after the cell has consumed it?

Good question, this is not obvious to many new users.

The logic is like this: In your PDE that describes the reaction and diffusion of your cytokine, you include a negative term (i.e. for decrease) that is nonzero where there is a cell and zero where there is no cell.

The attached model contains minimal example, resulting in this situation:

First, in `Global`, I defined a `Field` called `cytokine` with an initial concentration of 1.0 and diffusion.

``````<Field symbol="cytokine" value="1.0" name="Cytokine concentration">
<Diffusion rate="1"/>
</Field>
``````

Then, I defined a `System` with a differential equation with a negative term `-r*cell*cytokine` where `r` is the consumption rate of cells. (Here `r` is a constant, but it could also be a cell property to specify that each cell has its own consumption rate.)

``````<System solver="adaptive45">
<Constant symbol="r" value="0.1" name="consumption rate"/>
<DiffEqn symbol-ref="cytokine">
<Expression>             -r*cell*cytokine        </Expression>
</DiffEqn>
</System>
``````

Finally, I defined a `Constant` called `cell` which is 0 everywhere, except where there is a cell.
To do this, specify `cell` in `Global` and set it to `0`:

``````<Global>
<Constant symbol="cell" value="0" name="presence of cell"/>
</Global>
``````

But in `CellType`, the value of the constant `cell` is locally overwritten with a value of `1`:

``````<CellType class="biological" name="cells">
<Constant symbol="cell" value="1" name="presence of cell"/>
</CellType>
``````

In this way, the term "-r*cell*cytokine" is negative 'within' cells and zero outside. Therefore, the cytokine concentration is only decreased at locations with cells.

See the attached model for more details. Hope this helps!

Best,
Walter

consumption.xml