12th Congress of the European Hematology ... - Haematologica

12 th Congress of the European Hematology Association
0193
IMMUNE RECONSTITUTION OF THE T CELL COMPARTMENT IN HEMATOLOGICAL MALIG-
NANCIES FOLLOWING ALLOGENEIC NON MYELOABLATIVE HEMATOPOIETIC CELL
TRANSPLANTATION
P. Omedé, 1 B. Bruno, 2 M. Gilestro, 1 M. Spagnolo, 2 F. Ferro, 2
M. Ruggeri, 2 M. Brunetti, 2 S. Caltagirone, 2 C. Di Bello, 2 A. Fantauzzo, 2
L. Cimolin, 2 C. Sfiligoi, 2 S. Cena, 2 L. Giaccone, 2 F. Fiore, 2 M. Rotta, 2
R. Sorasio, 2 M. Boccadoro2 1 2 ASO San Giovanni Battista, TORINO; Divisione di Ematologia, TORINO,
Italy
Background and Aims. Allografting is a potentially curative therapy for
a variety of hematological malignancies. However, relapse and treatment-related
toxicity are major obstacles to cure. Reducedintensity/non-myeloablative
conditionings were designed to initially
establish hematopoietic mixed-chimerism and then to serve as a platform
for additional cell immunotherapy aimed at eradicating tumor cells
in medically unfit or elderly patients (up to 70 years). However, the risk
of post-transplant infections and the efficacy of graft-versus-tumor
effects also rely on the thymic function, potentially reduced with age.
For this reason it is mandatory to evaluate the residual thymic function.
Material and methods. The immune recovery of the T cell compartment
was evaluated by flow cytometry in 66 patients with hematological
malignancies, median age 54 years (range 34-64), conditioned with low
dose TBI (200 cGy), with/without fludarabine (90 mg/m 2 total), followed
by G-CSF mobilised peripheral blood stem cell infusion from HLA identical
siblings. The analyses were performed at different timepoints: baseline,
at day +28, at 3, 6 months, and at 1, 2, 3, 4, 5, 6 years post-transplant.
Briefly, fresh peripheral whole blood samples were red cell depleted
and stained with four-colour combinations with the following
MoAbs: CD3, CD4, CD8, CD16, CD45RA, CD45R0, CD62L. At least
80000 events for each combination were acquired on a FacsCalibur (Becton
Dickinson), and analysed with CellQuest Pro software. T cell Receptor
Excision Circles (TRECs) were evaluated by real-time quantitative
PCR with an ABI PRISM 7900HT Sequence Detection System at the
same timepoints. Results. Peripheral CD4+ T cells to >200/ul promptly
recovered by day +28 with median values of 274/uL, gradually increasing
to 474/ul, 682/uL, and 964/uL, at 1, 3 and 6 years, respectively. Naïve
CD4+CD45RA+bright T cells increased to 49/uL, 66/uL, 122/uL, at day
+28, and at 2, 6 years, respectively. Memory CD4+CD45R0+bright
remained stable with median values of 153/ul and 128/uL from day +28
through month +3, respectively; then increased to 234/uL, 332/uL,
529/uL, at 1, 2, 6 years. The evaluation of the coexpression of the CD45
isoforms showed that the number of CD4+CD45RA+CD45R0+ T cells
reached median values of 63/ ul by day +28 and 73/ul at 6 months; then
increased to 128/ul, 191/ul, 237/ul at 2, 5, 6 years, respectively. CD8+ T
cells reached median values of 156/ ul by day +28, increasing to 445/uL,
880/ulL, at 6 months, and at 4 years, respectively. CD4/CD8 ratio was
1.8 by day +28, decreased to 0.57 at 1 years, and then increasing at 0.9
at 4 years. In a subset of 35 patients the presence of naïve
CD4+CD62L+CD45RA+bright T cells and of memory CD4+CD62L-
CD45R0+bright T cells was evaluated. Preliminary data showed an
increase of these cell populations at 4 years with a median value of
836/ul, and 433/ul, respectively, while they remained stable at 5 and 6
years. TREC copies/100 ng DNA from peripheral mononuclear cells and
sorted CD4 cells were measured in 52 and 46 patients, respectively, at
the same timepoints: median baseline value from PBMC was 0.5, then
it gradually increased to 2.6 at 1 years, reached 53.7 at 5 years, and
remained stable at 6 years. A significant correlation was demonstrated
between TREC values from PBMC and CD4+CD62L+CD45RA+bright
T cells (p