ACCELERATED PLATELET RECONSTITUTION FOLLOWING TRANSPLANTATION OF BONE-MARROW CELLS DERIVED FROM IL-6-TREATED DONOR MICE

We transplanted bone marrow cells derived from normal donor mice treat ed with IL-6 to study the effect on the hematopoietic recovery of leth ally irradiated (8.5 Gy) recipients. Male Balb/C mice were treated for 7 days by continuous infusion of IL-6 (10 mu g/day). Not only did the se donor mice have increased numbers of circulating platelets as was p reviously shown; the numbers of circulating progenitor cells also incr eased more than 25-fold. Transplantation of nucleated bone marrow cell s derived from these donor mice into lethally irradiated female recipi ents resulted in increased platelet nadir counts in comparison to reci pients of normal bone marrow cells and similar to nadir counts of reci pients of normal donor bone marrow treated with IL-6 for 7 days after transplantation. Combination of transplantation of bone marrow derived from IL-6 treated donors with post-transplantation treatment of the r ecipients with IL-6 resulted in a further increase in nadir counts, al though it did not cause a further acceleration of platelet reconstitut ion. We conclude that transplantation of bone marrow cells modified in vivo by IL-6 results in significantly accelerated reconstitution of p latelets, to a degree similar to that observed following treatment wit h IL-6 after transplantation.