Pb2261 autologous transplantation of spleen tissue can recover splenic function after traumatic splenectomy

Background: Splenectomy has important consequences for the homeostasis of the immune system, with major involvement of B cell compartment. Autotransplantation of splenic tissue is a still debated therapeutic option for preserving splenic function after traumatic splenectomy. In our experience, the recovery of function of the splenic implant is complete after splenic autotransplant, as confirmed after 3 months by abdominal computed tomography and scintigraphy, but no data are available about long-term immune recovery. Aims: Detection of B- and T-cell function in patients who underwent splenic autotransplantation after traumatic splenectomy Methods: We evaluated the long-term follow-up of splenectomized patients by imaging, the amount micronucleated reticulocytes (MN-RET) as bio-marker of hemocatheresis, B and T subsets in peripheral blood, as bio-marker of immune dysregulation, by multi-parametric flow cytometry. Our series included 10 patients who received splenectomy after trauma, with 5 of them treated with splenic autotransplantation (Group A) and 5 not (Group B) and compared to 7 healthy subjects (Group C). MN-RETs were identified as fraction of erythrocytes negative for CD42b and positive for CD71 and propidium iodide, according to the procedure described by Dertinger Stephen D, (Mutation Research 2000). For evaluation of B-cell subsets, we used the Dura Clone IM B Cells kit (Beckman Coulter), a reagent panel of 8 monoclonal antibody: IgD (FITC), CD21 (PE),CD19 (ECD),CD27 (PC7),CD24 (APC),CD38 (APC-750), IgM (Pacidic Blue),CD45 (Krome Orange), according to the manufacturer's instructions. After gating on CD19 positive cells, the different expression of IgM, IgD, CD38 and CD27 allows to distinguish the following B-subpopulations: B-naıve, B-marginal zone, B-class-switched memory and B-class-unswitched memory. To identify the different T cell subsets, we used the kit Dura Clone IM T Cells (Beckman Coulter) a reagent panel of 10 monoclonal antibody: CD45RA (FITC), CCR7 (CD197)(PE),CD28 (ECD), PD1(PC5.5),CD27 (PC7),CD4 (APC),CD8 (A700),CD3(APC-750),CD57 (Pacific Blue),CD45 (Krome Orange), to identify CD4+ and CD8+ T-cells, and their PD1 expression. By the different expression of CCR7 and CD45RA we identified the following subsets of T-cells: naive, central memory, effector memory and terminal differentiated effector memory T-cells. Results: We did not observe significant differences in the percentage of both B-lymphocytes and T-lymphocytes in the three groups studied. However, splenectomized patients (group B) compared to healthy donors (group C) had an increase of naive B-lymphocytes (p = 0.03) and B cells marginal zone (p = 0.01) and a defect of class-unswitched (p = 0.007) and class-switched memory B cells (p = 0.05), associated to increased expression of the check-point inhibitor PD1 on CD8+T-lymphocytes (p = 0.08). For all evaluated subsets, patients in group A who received splenic autotransplantation did not show significant differences from healthy subjects, suggesting a partial recovery of immune splenic function and of hemocateretic activity. Summary/Conclusion: In patients underwent splenectomy there is an impairment of B and T cell functions as well as an altered hemocateretic activity that could be partially reverted by autologous spleen tissue transplantation. Taken together, our data, if confirmed on a greater number of patients, suggest that autotransplantation of splenic tissue could be sufficient to maintain a physiological immune splenic activity.