RICOSTITUZIONE IMMUNITARIA IN PAZIENTI SOTTOPOSTI A TRAPIANTO ALLOGENICO DI CELLULE STAMINALI EMOPOIETICHE: VALUTAZIONI A LUNGO TERMINE
Creators: name: VENDRAMIN, ANTONIO
Publisher: name: Universit� degli Studi di Milano
Year: 2012

description: Allogenic stem cell transplantation represents an important therapeutic option for the treatment of a number of haematological diseases. Particularly in the context of onco-haematological diseases this treatment has been shown to improve outcome thanks to the graft versus tumour (GVT) effect. Although recent improvements in transplantation procedures, still some limitations to the applicability of these treatment persist. First, not all patients may have available an HLA (human leukocyte antigens) identical donor and secondly, conditioning regimens before transplantation may be too toxic for elderly patients or for patients with other co-morbidities. To overcome this limitations in last few years many researchers have been exploiting new approaches. The introduction of not fully matched transplantations (mismatched or haploidentical) and reduced intensity regiments have partially overcome the limitations. In the onco-haematological context the most common complications of allogenic stem cell transplantation are relapse, opportunistic infections and activation of transplanted immune system against the normal tissues of the host (graft versus host disease ? GVHD). All of these represent alterations of the normal functions of the immune system and demonstrate the importance of monitoring immunity in allo-transplanted patients. Studies in these field are mostly limited to the evaluation of the first year after transplantation and data from longer follow up are limited. In this study we monitored patients undergoing haematopoietic stem cell transplantation from an alternative donor after reduced intensity regimen over one year after transplantation (up to 4-5 years after transplantation). Particularly we evaluated 6 patients (age at transplantation 34; range 15-49) undergoing haploidentical stem cell transplantataion associated with T cell depletion in vitro (immunomagnetic selection of CD34 stem cells) and in vivo (anti CD52 antibody ? Alemtuzumab) followed by infusion of CD8 depleted donor lymphocytes and 18 patients (age at transplantation 40; range 22-60) undergoing transplantation from a match unrelated donor (MUD) followed by in vivo T cell depletion (anti thymocyte globulins ? ATG). All the patients have been analysed at the times of clinical remission and not under pharmacological treatment. In order to compare data obtained by the single cohorts to a normal situation we also evaluated 10 healthy donors (age 37; range 24-55). The evaluation of the immune recovery has been carried out through 4 different techniques: - analysis of chimerism through amplification of 9 different short tandem repeats (STR); - evaluation of the lymphoid sub population B, T and NK (and their maturation stages) through flow cytometry immunophenotype; - analysis of the thymic productivity trough quantification of the episomal DNA sjTREC (signal joint T-cell receptor excision circle); - evaluation of the receptorial complexity of the T and B cell compartment trough analysis of the CDR3 (complementary determinating region 3) of the ? chain of the T cell receptor and of the heavy chain of the immunoglobulins. Our results show no significant differences between the two groups of patients analysed in the long term immune reconstitution, neither respectively the counts of the lymphoid sub population nor regarding the complexity values for the B and T cell receptors comparing the data to the ones from healthy subjects. We show a reduction in the thymic productivity that persist over 3 years post transplantation although there are no difference comparing the two cohorts of patients. Even though the counts of the main populations normalize between 1 and 2 years after transplantation the analysis of the maturation of the B and T cell compartments highlights the persistence of alterations in the normal maturation process in all the follow up points. Particularly both patients undergoing haploidentical or MUD transplantation present an increase in the B na�ve subpopulation and a decrease in the B memory subsets demonstrating an alteration in the normal B cell development probably due to an alteration in the normal function of the germinal center. Concerning the T cell compartment it has been seen a decrease in the production of na�ve T cells, that reflects the low thymic production, and an increase in the effector and terminal memory compartment. These might be a mechanism involved in the control of the oncological disease . In conclusion, patients that do not relapse and do not experience other clinical problems are able to recover immunity in the long term although thymic production remains low. No significant difference are found between the two types of transplantation highlighting that haploidentical transplantation is a good alternative to HLA identical transplantation implying less problems for donor recruitment. Analysis of the maturation steps of the B and T cell compartment demonstrated the persistence of alterations long term after transplantation indicating that this evaluation should be further studied in order to elucidate the mechanism at the basis of the immune recovery. Moreover this could be a good marker for monitoring the clinical course of the patients.