The ANALYSIS of Chimerism IN ACTIVATED T Lymphocites CD25+ Improves the CAPACITY of the T Lymphocytes CD3+ Chimerism Dinamic to Predict COMPLICATIONS AFTER Allogenic STEM CELL TRANSPLANTATION.

Abstract 4307 Introduction Complications after Allogenic Stem Cell Transplantation (Allo-SCT) are influenced by the immunological fenomena associated to the alloreactivity/allotolerance between donor and recepient. In this context, the usefulness of chimerism quantification in T lymphocytes for the prediction of complications after Allo-SCT is well known. However, to our knowledge, there is no information on the utility of chimerism analysis in activated lymphocytes (CD25+). Objective To stablish an asociation betwen the more common complications post Allo-Tph (aGVHD, cGVHD, relapse, reject), and the chimerism dynamics in CD25+ activated lymphocytes in the early period post-transplantation, trying to predict the patients with more risk of suffering from this complications. Materials and Methods The study included 38 Allo-SCT (17 NMA, 21 MA; 7 Haploidentical, 13 non-related donor, 18 identical donor; 7 UCB, 5 BM, 26 PB). Chimerism analysis was performed every 2 weeks until complete chimerism (CC) was achieved, and every 3 months thereafter. Follow up was censored when patients received DLI or 2nd Allo-SCT.Chimerism quantification was performed by microsatellite PCR (STR-PCR; AmpFlSTR SGM Plus; Applied Biosystems) on DNA obtained from peripheral blood and purified cell lineages (95% putity) by immunomagnetic technology (Miltenyi Biotec). Results [Table 1][1] shows the results at day +30 for T and activated lymphocytes (CD3+ and CD25+) allocating patients in two groups depending on the relative percentage of recipient cells (% rec) in both cell lineages. 20 patients were in CC in CD25+, maintening this CC during the study. 18 patients were found in MC in CD25+ (18/38 MC). 1/18 was in CC in CD3+ TL, and 10/18 were in CC in whole blood. 17/18 were in MC both in CD3+ and CD25+ lymphocytes, | | Day + 30 post Allo-Tph n=17 | |:--------- | --------------------------- | -------------------- | | | % rec CD25 >% rec CD3 | % rec CD3>% rec CD25 | | Patients | 12 | 5 | | aGVHD >1 | 5 (41%) | 1 (20%) | | cGVHD | 4 (33%) | 1 (20%) | | CQ day+90 | 7 (58%) | 5 (100%) | | Relapse | 4 (33%) | 0 (0%) | | Rejection | 1 (8%) | 0 (0%) | Table 1 Although no statistical significance is achieved due to the reduced sample size, patients in the first group (% rec higher in activated that in T lymphocytes) tend to achieve CC later and to show higher risk of developing complications such as acute and chronic GVHD, relapse or rejection. Conclusions A higher incidence of complications post Allo-SCT (aGVHD, cGVHD, relapse, rejection) in patients with % of recipient in CD25+> % recipient in CD3 at day 30. Chimerism analysis in activated lymphocytes (CD25+) is of great utility after Allo-SCT since it allows beter prediction of complications than standard follow up of whole blood or T lymphocytes. Disclosures: No relevant conflicts of interest to declare. [1]: #T1