Autologous Bone Marrow Transplantation - Blog Science Connections

354 Burkitts Lymphoma Purging Assay
each set of experiments the percentage of BL cells at day 10 within each
sample, set up with serial BL cell dilutions, provides a calibration curve (Fig 1).
Next, the effects of purging have been assessed in bone marrow samples
contaminated with 1% BL cells and treated either by a complement-mediated
cytolysis or immunomagnetic depletion. They were then grown in the same
conditions as the untreated samples. At day 10 of the culture, the percentage of
growing BL cells in the treated samples were compared with that in the
untreated samples, and the number of residual BL cells that escaped treatment
in each sample estimated (for example, see Fig 1). The estimates ranged from 1
in 10 3 (4000 total BL cells) down to 1 in 4 x 10 6 (i.e., 1 BL cell). The efficacy of
the purging procedure can thus be quantitated from 2 to 4.6 logs (decimal
logarithms) removal, or "kill," representing the outgrowth of cells related to the
initial number of BL cells in the unpurged samples.
During the experiments, two additional findings emerged. First, when the
samples contained more than 1 BL cell in 10 4
and the kill was less than 2 logs,
the final proportion of BL cells in cultures grown for 10 days reached 90-100%.
Consequently, this assay is not primarily suitable for measuring purging
methods of low efficiency without starting with more highly diluted BL cells. In
contrast, the assay described here is capable of detecting very low proportions
of residual BL cells after purging. Second, by keeping the samples for more
than 3 weeks in culture, it was possible to confirm the total elimination of all
growing BL cells by the purging method used (Table 2).
% BL ceils A
day 10 of
the culture |
100
calibration curve
without purging
80
60
40
20
0 1 4 40 400
Figure 1. Measurement of residual BL cells after purging.
^
Absolute number
of BL celia in
4.106 normal
ceils at start