Immunophenotypic Analysis Using CD80 and CD86 Staining Improves the Diagnosis of Waldenstrom's Macroglobulinemia by Evidencing a CD80+/CD86- Profile.
Authors: Toma Andrea , Poulain Stephanie , Grelier Aurore , Le Garff-Tavernier Magali , Davi Frederic , Brissard Martine , Bonnemye Patrick , Gueguen Stephanie , Musset Lucille , Azar Nabih , Morel Pierre , Leleu Xavier , Leblond Veronique , Merle-Beral Helene 
Published: October 2019

Abstract
Abstract 4389
The immunophenotypic characterization is an essential tool in the diagnosis of hematological malignancies but the immunophenotypic profile of Waldenstrom's macroglobulinemia (WM) B cells remains not clearly defined. In order to improve the diagnosis of WM by an immunophenotypic peripheral blood test, we studied within a multicentric protocol the expression of costimulatory molecules CD80 (B7.1) and CD86 (B7.2) on blood B-cells of WM patients diagnosed by monoclonal IgM in the serum and morphological lymphoplasmacytic bone marrow (BM) infiltration. Results were compared to those obtained in healthy controls and other chronic B-cell lymphoproliferative disorders (LPD). Immunophenotypic analysis was performed by flow cytometry using six-colour staining. The CD80 and CD86 staining was concomitant with usual analysis of standard antigens (kappa/lambda immunoglobulin light chains, CD20, CD19, CD79b, CD5, CD10, CD23, FMC7, CD38, CD25, CD43, CD11c, CD1c, CD27, IgM, IgD). We first analyzed 65 cases of WM and compared results to 13 healthy control subjects. Among the WM patients, 45 (69%) showed a monotypic kappa or lambda peripheral blood B-cell population with a Matutes score '3. In these patients, CD80 was always positive (>21% of B-cells) and CD86 negative (<18%). The mean responses obtained in WM compared to controls were: CD80 = 44.2±19.5% versus 13±4.6% (p<0.00001), CD86 = 5.4±5.3% versus 4.5±2.1% (p=0.18). Among the 20 patients without monotypic kappa or lambda B-cell population in peripheral blood, 13 showed a CD80+/CD86- profile (CD80 = 33±7.4%, CD86 = 7.6±4.4%). Six of them were studied by molecular aproach (PCR) showing the presence of a clonal B-cell population in all cases. Overall, 90% of WM patients showed a CD80+/CD86- profile in blood. Seven patients without peripheral monotypic kappa or lambda B-cell population evidenced a CD80-/CD86- profile; among them, one was tested by PCR and showed the lack of a clonal B-cell population in blood. We then studied other chronic B-cell LPD with peripheral blood neoplastic involvement by a monotypic kappa/lambda population, including 15 marginal zone lymphoma (MZL), 4 non-Hodgkin lymphomas (NHL) and 28 chronic lymphocytic leukemia (CLL). The mean expression of CD80 was 37±35.6%, 2.5±1.7%, 12.4±20.6%, and of CD86 30.5±38%, 19±27.5%, 15.4±19.3%, respectively. The expression of these antigens in MZL was heterogeneous, but a WM-type CD80+/CD86- profile was never observed in peripheral blood B cells. No NHL and 4 CLL (14%) exhibited a CD80+/CD86- profile. In conclusion, while immunophenotypic analysis usually performed with standard antigens does not allow to define a typical profile of WM, additional CD80 and CD86 staining in blood samples usefully improves the diagnosis of WM in the context of chronic B-cell LPD with peripheral blood involvement having a Matutes score '3. Furthermore, even in the absence of blood involvement detected by classical imunophenotypical aproach, the CD80 and CD86 staining may prove the presence of a peripheral blood monoclonal population, discriminating WM from other B-LPD with plasmatic IgM and lymphoplasmacytic BM infiltration, and diagnosing a WM in 90% of cases.

Disclosures:
No relevant conflicts of interest to declare.