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: In addition to renal allografts with TG , we also examined grafts with acute rejection , recurrent glomerulonephritis , chronic allograft nephropathy and stable grafts ( " protocol biopsies " ) .
### Output Text:
In addition to renal allografts with TG , we also examined grafts with acute rejection , recurrent glomerulonephritis , chronic allograft nephropathy and stable grafts ( " protocol biopsies " ) . 