Download immune status of chronically transfused patients

Li Chi-Kong
The Chinese University of Hong Kong, Hong Kong SAR
IMMUNE STATUS OF CHRONICALLY TRANSFUSED PATIENTS
Symposium 4, 11th International Conference on Thalassaemia & Haemoglobinopathies
Infection is the second commonest cause of death among transfusion dependent Thalassaemia
major (TM) patients. There are multiple factors contributing to the increase incidence of
severe infective and also the special types of infection in TM. Studies had been performed to
investigate the immune system and also its relationship to infection. In-vitro studies
demonstrated iron overload was associated with defective phagocytic activity of neutrophil
and monocyte, and also modulation of natural killer cell activity. Treatment with iron
chelator can partially correct the defective function. Splenectomy is associated with increased
incidence of infection especially encapsulated bacteria and gram negative bacteria. With
advances in transfusion therapy, splenectomy is less frequently performed. Deferiprone may
cause neutropenia or agranulocytosis in <1% of patients, and fatal infection may happen.
Immunomodulation after blood transfusion has been demonstrated in various studies.
Increased risk of post-operative infections favours the deleterious clinical effects of
transfusion immunomodulation, but it is debatable NK cell function has been shown but the
clinical significance is not certain. With the exposure to transfused foreign antigens, there is
increased in activation status of the white cells. Abnormalities in serum levels of cytokines
are common, including increased TNF, soluble CD8, sCD25 and lower sCD4. IL-6 and IL-8
was also increased in some studies. White cell in the transfused blood was considered as an
important cause of the immune changes. With more efficient leukodepletion by filters, the
immune changes may be ameliorated. With the above changes in the immune status, TM
patients may have partial functional immunodeficiency. However the multiple factors as
described above make the prediction of immune competency of an individual patient
difficult. Further studies are required to study the immune status in view of the new
development of transfusion practice, vaccination and chelation.