Page 315 - Essential Haematology

Chapter 23 Stem cell transplantation / 301

Figure 23.3 Peripheral blood
stem cell collection: enriched
+
CD34 cells stained by May –
Gr ü nwald - Giemsa stain. The cells
have the appearance of small -
and medium - sized lymphocytes.

the foreign ’ stem cells. An important development include agents such as fludarabine, low - dose irradia-
‘
that has occurred in SCT is a major shift from tion, antilymphocyte globulin or other antibodies
myeloablative regimens to non - myeloablative that delete T cells, and low doses of busulfan
conditioning. or cyclophosphamide. The aim in these

Myeloablative conditioning regimens irrevers- ‘ mini - or reduced - intensity - transplants ’ is to use
ibly destroy the haemopoietic function of the bone enough immunosuppression to allow donor stem
marrow with high doses of chemotherapy or radio- cells to engraft without completely eradicating host
therapy. TBI is usually used in patients with malig- marrow stem cells. Donor leucocyte infusions (DLI)
nant disease and is administered as a single dose or are commonly used at a late stage in order to
in smaller doses over several days ( fractionated ). Th e encourage complete donor engraftment. Such regi-
most commonly used chemotherapy drug is cyclo- mens extend the age range and increase the treat-
phosphamide but busulfan, melphalan, cytosine ment indications for allogeneic transplantation.
arabinoside, etoposide or nitrosoureas are given in
some protocols. At least 36 hours are allowed for
Post - t ransplant e ngraftment

the elimination of the drugs from the circulation
and i mmunity
following the last dose of chemotherapy before
donor stem cells are infused. Conditioning therapy After a period of typically 1 – 3 weeks of severe pan-

is often complicated by mucositis and patients cytopenia, the first signs of successful engraftment
sometimes need parenteral nutrition. Trials are are monocytes and neutrophils in the blood with a
taking place in which monoclonal antibodies subsequent increase in platelet count (Fig. 23.4 ).

directed against specific antigens such as CD45 are A reticulocytosis also begins and natural killer
attached to toxins or radioactive isotopes in an (NK) cells are among the earliest donor - derived
attempt to selectively target white cells as an aid to lymphocytes to appear. G - CSF may be used to
conditioning. reduce the period of neutropenia. Engraftment is
Non - myeloablative conditioning regimens usually quicker following PBSC transplantation
have been developed to reduce the morbidity and than BMT.

mortality of allogeneic transplantation and do not The marrow cellularity gradually returns to
completely destroy the host bone marrow. Th ese can normal but the marrow reserve remains impaired