[BioC] How to filter a list of genes by their ontology

[Laurent Pays [guest]]

Hi, 
After analysing my arrays for differentially expressed genes, I get a list of genes Id. To reduce even more the number of genes in this list, I would like to retain only genes related to the immune system. I've looked for packages dealing with "ontology" but I couldn't find any doing this simple task...

Any idea on what package/function I could use?

Thanks in advance for your help.

L.P

 -- output of sessionInfo(): 

R version 2.7.0 (2008-04-22) 
powerpc-apple-darwin8.10.1 

locale:
fr_FR.UTF-8/fr_FR.UTF-8/C/C/fr_FR.UTF-8/fr_FR.UTF-8

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base  

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