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

patient is still undergoing intensive chemotherapy and the outcome is
not known yet. We would conclude that not all transformation events
in CLL occur within the original clone. The majority appear to be clonally
distinct and a significant proportion of these appear to be EBV associated.
This presumably occurs as a result of both the underlying
immune-deficiency seen in CLL as well the potent immunosuppressive
agents given as therapy. This phenomenon may also be a feature of other
B-cell disorders as we have recently seen a phenotypically and genotypically
distinct EBV associated DLBL in a patient treated with chlorambucil,
CHOP and FCR for mantle cell lymphoma. The natural history of
these tumours remains uncertain at this stage but it is clear that at least
a minority may resolve spontaneously. All biopsies demonstrating histological
transformation in CLL patients should be assessed for the presence
of EBV.
1083
RH-INCOMPATIBLE PLATELET TRANSFUSIONS AND EVALUATION
OF ANTI-D ALLOIMMUNIZATION
S. Misso, 1 L. Paesano, 2 M. D’Onofrio, 2 B. Feola, 1 G. Fratellanza, 3
E. D’Agostino, 3 S. Marotta, 1 A. Minerva1 1 Hospital S. Sebastiano and S. Anna, CASERTA, Italy; 2 Hospital S. Giovanni
Bosco, NAPLES; 3 University Federico II, NAPLES, Italy
Background. Transfusions of platelet concentrates (PC) are indicated
both for the prophylaxis of bleeding and for thrombocytopenic patients.
PC can sometimes contain enough red blood cells to cause immunization
against antigens of the Rh system, thus Rh D+ PC should not be
transfused to Rh D- female patients in child-bearing age. Moreover, the
platelet membrane carries numerous structures with varying degrees of
antigenic potential, including substances A and B absorbed from the
plasma. For these reasons, platelets are transfused according to the following
criteria: a) ABO-matched to the recipient; b) according to compatibility
of plasma; c) platelets suspended in a crystalloid solution. Aims.
The aim of our study was to evaluate anti-D alloimmunization caused
by transfusions of Rh incompatible platelets, produced from plateletrich
plasma, in both immunosuppressed and immunocompetent subjects.
Methods. 115 Rh D- patients, with not detectable irregular antibodies
prior to transfusion, were studied in Caserta’s Hospital and in
University. 58 of them were affected with onco-hematological disorders
(12 with acute leukemia, 21 with Non-Hodgkin’s lymphoma, 15 with
myelodysplastic syndrome and 10 with chronic myeloid leukemia in
blast crisis); these had undergone chemotherapy for their malignancy and
some had received conditioning therapy for a subsequent bone marrow
transplant; the supportive therapy was based on transfusion of red blood
cell (RBC) concentrates selected for both ABO and Rh compatibility and
PC administered regardless of Rh compatibility. The others were 45 surgical
and 12 neonatal patients, which received Rh-matched RBC transfusions
but unmatched PC. Rh incompatible platelet administration was
carried out because transfusion therapy could not be delayed and compatible
blood components were not available. However, the blood components
for all the hematological patients and for the variably immunosuppressed
patients were filtered at the bed-side. The indirect antiglobulin
test, by gel-test, was carried out, in all patients, before the first transfusion
and repeated 1 month after the last one. Results. 562 PC, obtained
from single units of whole blood, were transfused. ABO compatibility
was respected in only 43% of the cases. On average every transfusion
episode consisted of 5/6 units of platelets. No one of the Rh-negative
hematological or pediatric patients developed alloimmunization. On the
contrary, 3 on 45 surgical patients (6.6%) showed alloimmune antibodies:
two anti-D (4.4%) and one anti-E (2.2%) were identified. Alloimmunizations
became detectable by laboratory tests 37±4 days after the first
transfusion. Conclusions. The incidence of anti-D alloimmunization has
been reported to range between 0-19% in immunosuppressed patients
and to be greater than 80% in immunocompetent subjects. Our data
differed from that in literature, in fact we found no cases of alloimmunization
among immunosuppressed patients. This is because hematological
patients received strongly immunosuppressive chemotherapy and
newborns were not immunocompetent yet. Despite the limited sample
size, we can conclude that: the risk of alloimmunization from incompatible
platelet is low, but does exist; this risk is related with the volume
(>0.03 mL) of RBCs contaminating the PC and it might be inversely
related to immunomodulation due to massive or prolonged transfusion
therapy.
12 th Congress of the European Hematology Association
1084
CHARACTERIZATION OF IG VH4-34 EXPRESSED BY CHRONIC LYMPHOCYTIC LEUKEMIA
(CLL) PATIENTS IDENTIFIES A SUBSET WITH A VIRTUALLY IDENTICAL HEAVY AND LIGHT
CHAIN THIRD COMPLEMENTARY DETERMINING REGION (HCDR3 AND LCDR3)
E.M. Ghia, 1 S. Santangelo, 2 M. Marinelli, 2 I. Del Giudice, 2 R. Maggio, 2
N. Peragine, 2 F.R. Mauro, 2 M.S. De Propris, 2 D. Capello, 3 G. Gaidano, 3
A. Guarini, 2 R. Foa’ 2
1 University La Sapienza, ROME, Italy; 2 University La Sapienza, ROME, Italy;
3 Division of Hematology, Amedeo Avogadro, NOVARA, Italy
Previous studies suggest that the Ig heavy and light chain variable
region (VH and VL) repertoire expressed by patients affected by CLL is
restricted. Evidence of biased Ig heavy and light chain variable region
genes indicates a possible response to a common antigen epitope. To further
explore the antigen-driven selection in CLL, we focused on CLL
patients expressing the VH4-34 gene. DNA was extracted from peripheral
blood mononuclear cells isolated from 126 CLL patients studied at
diagnosis at a single institution (patients selected by age less than 65
years, median age: 50±9). PCR amplification was performed using VH
family specific and consensus JH primers, followed by automated
sequencing. VH4-34 light chains were sequenced using VL and JL primers.
The sequences were aligned to Ig sequences from the IMGT, GeneBank
and V-BASE databases. The VH family gene usage was the following:
VH1 17%, VH2 2%, VH3 45%, VH4 32%, VH5 2%, VH6 1% and VH7
1%. Mutated VH genes (98% homology to germline sequence) were 26%. Within the VH4 gene
family, the most frequent gene was VH4-34 (56%); only one of the 23 cases
expressing VH4-34 was unmutated. The majority of mutated VH4-34
(16/22 cases, 73%) had homology 96% and