Preferably {HEAD ~ the fluids} contain blood or blood products and comprise {TAIL ~ biologically active proteins} 
comprise
Preferably { HEAD ~ the fluids } contain blood or blood products and comprise { TAIL ~ biologically active proteins }
OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL