Ratio ofblood andmarrow-derived cells inbone marrow transplantation

Inbonemarrowtransplantation inman,amixture ofbloodandmarrowisaspirated fromthedonor andinjected intravenously totherecipient. To obtain enoughcells (usually considered to be >2 x 108/kg bodyweight) thevolume ofaspirate mustapproach onelitre, ofwhichitcanbeassumed that980% orsoisactually blood andless than20% isderived fromthemarrowitself. Thiscell mixture isinsharp contrast withthat usedinmarrowtransplants inmice, wherefemoral marrowcells forman inoculum whichisvirtually free ofblood contamination. Furthermore, itisanoldobservation that in micegraft vhost(GvH)reactions arerelatively uncommonanddifficult toinduce bysuchmarrow suspensions, whereas theaddition ofblood, lymph nodeorspleen cells greatly enhances theincidence andseverity ofGvHreactions.1 Similar observations indogsandotherspecies confirm thegeneral validity ofthehypothesis thatitiscells fromthe bloodpresumptively T lymphocytes-which are theprecipitating causeofGvHdisease.2 3 Whatisnotknownistheactual composition of theblood-marrow mixture inhumantransplants andwhether itisrelated toGvH disease. Inparticular, theincreased susceptibility toGvH disease if