An improved clonal excess assay using flow cytometry and B-cell gating
BW Letwin, PK Wallace, KA Muirhead, GL Hensler, WH Kashatus and PK Horan
Smith Kline & French Labs, King of Prussia, PA.
In humans with B-cell malignancies, the presence of monoclonal B
lymphocytes (clonal proliferation) can be detected by comparing the
fluorescence intensity distributions of lymphocytes stained with anti-
kappa and anti-lambda reagents. The sensitivity of previously described
single-color immunofluorescence techniques to low levels of clonal excess
is limited by background from cytophilic immunoglobulins on non- B cells
and by the low proportion of circulating B cells in individuals with
minimal disease. We have used two-color immunofluorescence and B- cell
gating to develop an improved assay that avoids false positives due to
non-B cells, without requiring restrictive light scatter gates that may
exclude true positives. This method is sensitive to 0.2% monoclonal B cells
admixed with fresh normal lymphocytes, to 0.6% monoclonal B cells admixed
with normal lymphocytes that have been stored for up to 72 hours, and
readily detects 1% monoclonal cells in patient specimens. The two color
B-cell gated assay offers sensitivity equivalent to the single-color assay
and improved specificity for detection of low levels of clonal excess.
Volume 75,
Issue 5,
pp. 1178-1185,
03/01/1990
Copyright © 1990 by The American Society of Hematology
