Autologous Bone Marrow Transplantation - Blog Science Connections

Purging Methods in Burkitt's Lymphoma 363
very sensitive to the complement lysis; in contrast, the IMD procedure provided
an optimal BL cell elimination on the BLg 3
cell line partially resistant to
complement. The analysis of individual experiments, in which one or the other
procedure failed, supplied complementary data, as shown in the three
examples of Table 3. Indeed, we demonstrated a complementarity between the
two immunologic procedures. It has been previously reported that chemical
(mafosfamide) and immunologic purging methods have additive effects
(6-10). Such a complementary effect could appear more surprising in the case
of two immunologic methods. It is in fact quite logical if one remembers that the
resistance of malignant cells to complement lysis (as shown for BL 9 3
) is
relatively independent of the monoclonal antibody used and that quality criteria
required from monoclonal antibodies and the recognized antigen in the IMD are
different from those required in the complement lysis procedure (see V.
Combaret et al. in this volume).
CONCLUSION
Our work shows that one or the other procedure enables us to purge a
bone marrow having minimal involvement (i.e., 1% or less), but a few
unpredictable partial failures were observed with both methods. Considering
such results, we are tempted to propose combining the purging methods, to
allow the cleansing of bone marrow contaminated by more than 1% malignant
cells and to avoid the few failures we observed. We will, however, strongly reject
such an idea. Indeed, in the first hypothesis, if the marrow contains more than
156 malignant cells, it could probably be purged by a combination of these
procedures, but the peripheral disease would not be eradicated by high-dose
chemotherapy. In the second hypothesis, in order to avoid a few failures in some
patients it is unacceptable to increase for all of them the toxicity and the cost of
the purging by combining two procedures. We will, therefore, suggest a purging
"a la carte" for which optimal monoclonal antibodies and consequently optimal
methods will be selected for each patient in a preclinical assay (4; see also 1.
Philip et al. in this volume). Such an approach is certainly a very difficult one for
laboratory investigators but could allow the evaluation of the purging method
Table 3. Complementary Effects of Two Immunologic Procedures
Mean Cell Kill
(log)
Cell
Line
Complement
Magnetic
Depletion
BL99 >5 2
BL93 2 >5
BL 2 >5 3
Note: These three individual experiments (one on each line) are part of Table 2
results and are given as examples. When one of the two techniques fails, the other one
is highly
efficient.