Localization of monoclonal B-cell populations through the use of Komogorov-Smirnov D-value and reduced chi-square contours

Flow cytometric clonal excess analysis of peripheral blood, routine handling, and pitfalls in interpretation

Clonal excess (CE) analysis by flow cytometry is a convenient method to detect minimal involvement of peripheral blood and bone marrow by B-cell lymphoma. The method is based on evaluation of the congruity between kappa and lambda light chain distributions within a normal B-cell population. By using the Kolmogorov-Smirnov method for evaluation of histogram identity, the maximum difference (D value) between distributions is calculated. However, variable adsorption of cytophilic plasma immunoglobulin (Ig) to CD16 positive cells, T-cell subsets, and the B cells themselves may cause incongruity between the light chain distributions that might simulate or disguise a true clonal excess and thus create major pitfalls in the interpretation of the CE analysis. These phenomena are observed both in normal blood donors and in patients with non-Hodgkin's lymphoma. In the present report we describe: (1) how freezing of the isolated mononuclear cells before immunostaining effectively removes most of the adsorbed cytophilic Ig, (2) how by exclusion of the CD16 positive population further resolution of the relevant histogram shape is obtained to avoid false interpretations of incongruity, and (3) how adsorption of Ig to B-cells creates a typical pattern of "reciprocal labeling" that can be mistaken for a clonal excess. Based on our observations we argue against an uncritical use of normal D values for definition of clonal excess and advocate an analytic evaluation of the kappa and lambda overlay distribution by dual immunofluorescence, either by excluding CD16 positive cells or by including only B cells, to reveal the nature of the different deviations.

Comparison of poly- and monoclonal antibodies for determination of B-cell clonal excess in an routine clinical laboratory

Flow cytometry (FCM) has gained wide use in the determination of clonality in B-cell lymphoproliferative diseases and many methodological variations exist. We have compared the suitability of a) dual fluorochrome (FITC/PE)-labelled monoclonal antibodies, b) single fluorochrome (FITC)-labelled monoclonal antibodies and c) F(ab')2 fragments of FITC-labelled polyclonal antibodies for flow cytometric determination of clonality using commercially available software and a short sample preparation protocol. The FCM method was validated by analysis of immunoglobulin heavy chain and light chain gene rearrangements. We recommend the use of FITC-labelled monoclonals to obtain three parameters, the kappa/lambda ratio, D and D/S(n) values (Kolmogorov-Smirnov statistics) instead of the commonly used kappa/lambda ratio and D values only. This allows the use of a rapid sample preparation protocol to blood and bone marrow aspirates without sacrificing sensitivity or specificity obtained by the usual FCM method.

Concomitant delineation of surface Ig, B-cell differentiation antigens, and HLADR on lymphoid proliferations using three-color immunocytometry

Accurate and consistent enumeration of B-cell subpopulations in lymphoid tissue was achieved through multiparameter three-color immunofluorescence and flow cytometric analysis (FCM). Phycoerythrin (PE)-anti-CD19 (Leu12) and biotinylated anti-HLADr/streptavidin-Duochrome (PE/Texas Red), used in conjunction with polyclonal fluorescein isothiocyanate (FITC) conjugated anti-surface immunoglobulin (SIg) antibodies, effectively separated non-specific binding and background fluorescence from true B-cell surface FITC immunofluorescence, while concomitantly analyzing for HLADr and CD19 phenotypic expression/deletion. Autofluorescence was measured to establish a fluorescence threshold. A second control measured non-specific binding of isotypic control mouse Ig and non-immune rabbit IgG. Cell suspensions from 128 samples of various lymphoid proliferations were studied. In 116 of the 128 samples, kappa/lambda ratios determined by flow cytometry correlated well with immunocytology results obtained using cytospins from the same cell suspension and with histopathologically established diagnosis. Clonality and lineage as defined immunotypically by flow cytometry was concordant with genotypic results in 64 of the 67 cases evaluated. SIg, HLADr, and CD19 deletions were demonstrated by flow cytometry in 8, 4, and 1 case(s), respectively. Discordance was usually attributable to selective loss of large neoplastic cells in flow cytometry specimens or absent expression of SIg by some cytoplasmic Ig (CIg+) lymphomas.

Lectins as probes to Pneumocystis carinii surface glycocomplexes

The binding characteristics of a panel of commercially available FITC-conjugated lectins to Pneumocystis carinii (Pc) were assessed by fluorescence microscopy and flow cytometry. Rat Pc obtained from infected lung homogenates were incubated with FITC-conjugated lectins in a series of concentrations, counterstained with propidium iodide, and analyzed for percent fluorescence and fluorescence intensity. All organisms bound concanavalin A and Wisteria floribunda agglutinin, 2 representatives of the glucose/mannose-binding group. From the lectin group specific for N-acetylglucosamine, Pc reacted more strongly with wheat germ agglutinin than with Solanum tuberosum agglutinin or Griffonia simplicifolia II lectin. Pneumocystis treated with lectins specific for N-acetyl-D-galactosamine and galactose exhibited much variation; the cells reacted moderately well to soybean agglutinin and less to Bauhinia purpurea, Maclura pomifera and Dolichos biflorus agglutinins and Griffonia simplicifolia I lectin. Arachis hypogaea agglutinin, Viscum album agglutinin and Griffonia simplicifolia I-beta 4 lectin had not effect. The organisms reacted weakly with Ulex europeus I agglutinin which is specific for fucose and did not react with Limax flavus lectin, which is specific for sialic acid. Competitive inhibition studies using relevant carbohydrates were performed to indicate that the positive reactions were specific. These studies should help to elucidate the mechanisms of attachment and pathogenesis of this organism.