In the sentence extracted from biomedical literature, identify all the chemical entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="chemical"> to denote a chemical.

### Input Text: Activated peripheral blood T cells from patients with psoriasis tended to exhibit greater spontaneous or dexamethasone - induced apoptosis than did normal T cells , particularly in the presence of sirolimus .
### Output Text:
Activated peripheral blood T cells from patients with psoriasis tended to exhibit greater spontaneous or <span class="chemical">dexamethasone</span> - induced apoptosis than did normal T cells , particularly in the presence of <span class="chemical">sirolimus</span> . 