A HUMAN-SCID-MOUSE-ISLET TRANSPLANT MODEL FOR THE EVALUATION OF THE REGULATORY ACTIVITY OF DONOR BONE MARROW CELLS.

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A HUMAN-SCID-MOUSE-ISLET TRANSPLANT MODEL FOR THE EVALUATION OF THE REGULATORY ACTIVITY OF DONOR BONE MARROW CELLS.
James M. Mathew, PhD , Silvia Alvarez BS , Teresa Vallone MT , Bonnie B. Blomberg, PhD , Miller Joshua MD and Violet Esquenazi PhD . Surgery and Miami FL, USA, University of Miami & VA Medical Center, 33136, Microbiology & Immunology .

Since certain experimental protocols cannot be carried out in humans and since animal studies may not reflect what may be relevant clinically, we have developed a SCID- mouse-human islet transplant model and have used it to evaluate regulatory activity by human donor bone marrow cells (DBMC).
It was observed that the levels of C-peptide (estimated using a competitive radioimmunoassay) were proportional to the number of purified human islets transplanted, and that the most cellularly economical dose with measurable human C-peptide levels was 3,000 islet-equivalents per animal. Similarly, intraportal injection was found to give higher C-peptide levels than sub-renal capsular implantation of the islets. Even though maximal reconstitution was observed in mice that received 20x10⁶ fresh PBL and 20x10⁶ anti-CD3 activated PBL, the development of GvHD was severe with the animals dying by day 40. The reconstitution was measured by flow cytometric analysis and enzyme-linked immunosorbent assay of peripheral blood leukocytes and plasma human IgG levels respectively. The animals that received 20x10⁶ anti-CD3 activated PBL on day 3 followed by 20x10⁶ alloactivated PBL each on days 5 and 7, demonstrated good reconstitution with upto 40% human cells in their peripheral circulation and no discernible GvHD. More importantly, the latter method of reconstitution was associated with rejection of the transplanted islets and this rejection could be abrogated by co-injection of the animals with DBMC. These in vivo results confirmed our previous in vitro observations that DBMC has a regulatory activity. This hu-SCID mouse islet transplant model will be used for further analysis of the immunoregulatory role of donor bone marrow cells.