Phenotypic heterogeneity of B- and T-cell differentiation antigens in B-CLL

Proposals for a Phenotypic Classification of B-Chronic Lymphocytic Leukemia, Relationship with Prognostic Factors

Immunophenotypic analysis was performed in 53 cases of B chronic lymphocytic leukemia using a large panel of monoclonal antibodies recognizing B, T, activation and myeloid antigens. Our results showed four patterns of reactivity: (a) several molecules were constantly expressed: CD19, CD20, CD24, CD37, HLA-DR, mu heavy chain, CD5, CD23, B5, CD32; (b) one antigen, CD11b, was found in 50 to 80% of the cases; (c) some markers were detected in less than 50% of the cases: CD25, CD38, CD71, CD11a, c, CD14b-c; (d) CD2 and CD16 were never detected. From these results, a phenotypic classification in three groups has been proposed and these groups were correlated with the progression of the disease, mainly with the lymphocyte doubling time of less than one year. We hypothesized that the leukemia cells could be at various stages of differentiation and/or activation according to their expression of activation and myeloid markers.

The Splenic White Pulp in Chronic Lymphocytic Leukaemia: A Microenvironment Associated with CR2 (CD21) Expression, Cell Transformation and Proliferation

Splenectomy specimens from 8 cases of chronic lymphocytic leukaemia (CLL) were examined. The infiltrate in the red pulp consisted predominantly of small lymphocytes. In contrast the predominant cells in the white pulp were pro-lymphocytes and para-immunoblasts. The Ki67 marker, which identifies cells in growth phase, was also concentrated among the transformed cells in the white pulp. Staining with monoclonal antibodies for CD21, which identifies the CR2 receptor, showed that the cells in the white pulp were strongly positive in contrast to those in the red pulp which were weak or negative. These findings suggest that factors present in the white pulp promote transformation and proliferation of CLL cells.

CD23 antigen density is related to serum gamma globulin level, bone marrow reticulin pattern, and treatment in B chronic lymphocytic leukemia

The CD23 antigen density was evaluated by a cytofluorometric technique in 55 patients with chronic lymphocytic leukemia. The quantification method was based on the use of biological standards in indirect immunofluorescence. The CD23 antigen density was correlated with the percentage of CD23 positive cells, but antigen density appeared to be a more informative parameter. CD23 antigen density was lower in stage B than in stages A or C patients, and higher in patients undergoing chemotherapy or previously treated than in untreated patients. There was a significant negative correlation between CD23 antigen density and serum gamma globulin and IgG levels, that existed only in patients in an advanced stage of the disease. CD23 antigen density was higher in patients with abnormal bone marrow reticulin pattern. Serum gamma globulin level was lower in these patients, as well as in patients with prognostically unfavorable histologic bone marrow infiltration pattern. These data emphasize the interest of antigen density as an additional parameter and the complex relationship between CD23 expression, hypogammaglobulinemia, bone marrow histologic findings, and treatment in chronic lymphocytic leukemia.

Immunoglobulin V gene expression in CD5 B-cell malignancies

Chronic lymphocytic leukemia (CLL) and small lymphocytic lymphomas (SLL) generally are malignancies of CD5 B cells. Immunophenotypic and clinicopathologic data, however, are required to distinguish subtypes that apparently have a different cytogenesis than that of conventional CLL or SLL. In addition to expressing CD5, neoplastic cells of the latter are also distinctive in that they frequently coexpress surface immunoglobulin (Ig), bearing one or more cross-reactive idiotypes (CRIs) (e.g. 17.109, G6,) that commonly are found on monoclonal IgM autoantibodies. The frequent occurrence of such CRIs reflects both the biased rearrangement and subsequent selected expression of Ig V genes with little or no somatic mutation. IgM/L CLL, for example, frequently (8/33) harbor abortive Ig rearrangements involving Humkv325, the VK gene encoding the 17.109-CRI. Also, the VH1 gene(s) encoding the G6 CRI accounts for over 10% of all VH genes and over 60% of all the VH1 genes used in randomly selected common CLL/SLL. Furthermore, comparison with the Ig expressed by nonmalignant G6 CRI+ B cells reveals an apparent restriction in the CDR3 of IgH expressed by G6 CRI+ CLL. Coupled with the observed potential bias in antibody light chain and heavy chain pairing in B-CLL, these data suggest that the autoantibodies expressed in this disease are selected based on antigen-binding activity. Collectively, our studies indicate that nonstochastic Ig V gene rearrangement and subsequent selection may influence the Ig repertoire expressed in this common B-cell malignancy.

Diagnostic and prognostic significance of myelomonocytic cell surface antigens in acute myeloid leukaemia

Thirty-six cases of acute myeloid leukaemia (AML) were tested with a large battery of monoclonal antibodies (moAbs) detecting surface markers normally expressed by myelomonocytic, T and B lymphoid, megakaryocytic and erythroid lineages. Differences in antigenic expression were observed among the various FAB subgroups: HLA-class II molecules were found in almost all AML cases but not in the promyelocytic subgroup (M3); CD14 and CD36 antigens were detected in monocytic leukaemias (M4 and M5); the CD34 moAb (MY10) recognizing an epitope described on myeloid stem cells was positive in 88% of the M1 and 80% of the M3 cases. By a multivariate analysis, only the CD14b (MY4) discriminated significantly between M1-M2 and M4-M5 subgroups. Using Cox's model to assess the prognostic importance of variables including immunophenotyping on survival, we undertook a one by one analysis and found that the presence of CD17 antigen predicted for a shorter survival (P = 0.03). In addition this marker appeared more significant than other clinical and biological parameters.

CD1 expression on B-CLL lymphocytes

In a previous report we showed that D47 CD1a monoclonal antibody positively labelled B-CLL cells of some patients. Six cases were selected to further characterize CD1 antigenic expression at the leukaemic cell surface using flow cytometry with a battery of six CD1a, two CD1b and two CD1c monoclonal antibodies. CLL cells were positively labelled with CD1a antibodies except OKT6 and NA1/34; in all cases they were CD1b negative and CD1c positive. These results suggested that CD1a, c epitopes can be detected on leukaemic B cells in addition to other T cell differentiation antigens. In view of recently published data demonstrating the presence of CD1c molecule in normal B cell subsets, our results further question the relationship of B-CLL with a restricted subpopulation of B cells.