CD180 Expression in B-Cell Lymphomas: A Multicenter Geil Study

CD180 is a Toll-Like Receptor homolog strongly expressed on normal human B-cells and involved in innate immune responses. Previous proteomic analyses on microparticles derived from mature B-cell neoplasms allowed us to identify CD180 as a marker of marginal zone lymphomas (MZL)(Miguet, Leukemia, 2013). Using flow cytometry on blood samples we showed that this protein is lost or underexpressed at the plasma membrane for almost all B-cell lymphomas except MZL. In order to confirm its clinical relevance, we conducted a prospective multicenter flow cytometry study in 5 French University Hospital laboratories, on behalf of the GEIL. Blood or bone marrow samples from 236 patients were studied (20 normal controls ; 74 chronic lymphocytic leukemia (CLL); 21 mantle cell lymphoma (MCL); 42 lymphoplasmacytic lymphoma (LPL); 13 follicular lymphoma (FL) ; 58 MZL, 14 of which with numerous villous lymphocytes; 8 hairy cell leukemia (HCL)). Analyses were performed either on FACSCanto II (BD Biosciences, 3 centers) or on Navios (Beckman Coulter, 2 centers) instruments. Harmonization process was performed using Rainbow beads (Spherotech).

For the CLL group, CD180 Median fluorescence (MdFI) in each center was not significantly different (Anova test, p>0.05). Instruments’ harmonization was therefore effective enough to obtain similar data from all centres. In the whole cohort, CD180 was significantly less expressed in the group of lymphomas -including CLL, MCL, LPL and FL- than in controls (Mann-Whitney test, p<0.05). Conversely, in the group of MZL and HCL, CD180 MdFI was not different from those of controls (Mann-Whitney test, p>0.05) but significantly higher than in CLL, MCL, LPL and FL (Mann-Whitney test, p<0.0001). Distinction between MZL and lymphomas with numerous villous lymphocytes was possible (Mann-Whitney test, p=0.0012) but not between MZL and HCL. ROC curve analysis determined a CD180 MdFI threshold of 1800 which allow the positive diagnosis of MZL with a sensitivity of 77% and specificity of 92%.

These results underline the efficiency of CD180 as a single positive and robust marker for MZL diagnosis, and confirm that between centers and between instruments harmonization is largely feasible in routine practice as published recently (Solly F et al. Cytomery part A, 2013). It should be emphasized that among the group of lymphomas with intense expression of CD180, all interestingly originating from the spleen, those with numerous villous lymphocytes display the highest expression. We described for the first time in this study the strong positivity of CD180 in HCL. Anti-CD180 antibody may be included in diagnosis combination markers in order to improve the diagnosis of chronic B-cell malignancies