A cytomorphological and immunohistochemical profile of aggressive B-cell lymphoma: high clinical impact of a cumulative immunohistochemical outcome predictor score

We analyzed morphological and immunohistochemical features in 174 aggressive B-cell lymphomas of nodal and extranodal origin. Morphological features included presence or absence of a follicular component and cytologic criteria according to the Kiel classification, whereas immunohistochemical studies included expression of CD10, BCL-2, BCL-6, IRF4/MUM1, HLA-DR, p53, Ki-67 and the assessment of plasmacytoid differentiation. Patients were treated with a CHOP-like regimen. While the presence or absence of either CD10, BCL-6 and IRF4/MUM1 reactivity or plasmacytoid differentiation did not identify particular cytomorphologic or site-specific subtypes, we found that expression of CD10 and BCL-6, and a low reactivity for IRF4/MUM1 were favourable prognostic indicators. In contrast, BCL-2 expression and presence of a monotypic cytoplasmic immunoglobulin expression was associated with an unfavourable prognosis in univariate analyses. Meta-analysis of these data resulted in the development of a cumulative immunohistochemical outcome predictor score (CIOPS) enabling the recognition of four distinct prognostic groups. Multivariate analysis proved this score to be independent of the international prognostic index. Such a cumulative immunohistochemical scoring approach might provide a valuable alternative in the recognition of defined risk types of aggressive B-cell lymphomas.     

Early Growth Response Genes 2 and 3 Regulate the Expression of Bcl6 and Differentiation of T Follicular Helper Cells

T follicular helper (Tfh) cells support differentiation of B cells to plasma cells and high affinity antibody production in germinal centers (GCs), and Tfh differentiation requires the function of B cell lymphoma 6 (BCL6). We have now discovered that early growth response gene 2 (EGR2) and EGR3 directly regulate the expression of Bcl6 in Tfh cells, which is required for their function in regulation of GC formation. In the absence of EGR2 and -3, the expression of BCL6 in Tfh cells is defective, leading to impaired differentiation of Tfh cells, resulting in a failure to form GCs following virus infection and defects in production of antiviral antibodies. Enforced expression of BCL6 in EGR2/3-deficient CD4 T cells partially restored Tfh differentiation and GC formation in response to virus infection. Our findings demonstrate a novel function of EGR2/3 that is important for Tfh cell development and Tfh cell-mediated B cell immune responses.     

Hypergammaglobulinemia in an SIV-infected rhesus macaque with a B-cell neoplasm with plasma cell differentiation

An SIV-infected rhesus macaque presented with anemia, hypercalcemia, and hyperglobulinemia. Neoplastic round cells with plasma cell morphology infiltrated multiple organs and stained immunohistochemically positive for CD45, MUM1/IRF4, CD138, VS38C, and Kappa light chain and variably positive for CD20 and CD79a, consistent with a B-cell neoplasm with plasma cell differentiation.     

Selective induction of DNA repair pathways in human B cells activated by CD4+ T cells

Greater than 75% of all hematologic malignancies derive from germinal center (GC) or post-GC B cells, suggesting that the GC reaction predisposes B cells to tumorigenesis. Because GC B cells acquire expression of the highly mutagenic enzyme activation-induced cytidine deaminase (AID), GC B cells may require additional DNA repair capacity. The goal of this study was to investigate whether normal human B cells acquire enhanced expression of DNA repair factors upon AID induction. We first demonstrated that several DNA mismatch repair, homologous recombination, base excision repair, and ATR signaling genes were overexpressed in GC B cells relative to naïve and memory B cells, reflecting activation of a process we have termed somatic hyperrepair (SHR). Using an in vitro system, we next characterized activation signals required to induce AID expression and SHR. Although AID expression was induced by a variety of polyclonal activators, SHR induction strictly required signals provided by contact with activated CD4⁺ T cells, and B cells activated in this manner displayed reduced levels of DNA damage-induced apoptosis. We further show the induction of SHR is independent of AID expression, as GC B cells from AID -/- mice retained heightened expression of SHR proteins. In consideration of the critical role that CD4⁺ T cells play in inducing the SHR process, our data suggest a novel role for CD4⁺ T cells in the tumor suppression of GC/post-GC B cells.     

Development of a monoclonal antibody, anti-6C2, which is involved in the interaction of CD4 T helper cells and activated B cells.

We have developed a mAb anti-6C2, by immunizing mice with T cell line derived from the Callithrix jacchus (common marmoset). Anti-6C2 is reactive with approximately 50% of unfractionated T cells, 50% of CD4+ cells, and 40% of CD8+ cells. Regarding CD4+ cells, anti-6C2-reactive cells substantially overlap with the CD29+CD45RO+ Th cell population. Moreover, anti-6C2 can divide these T cells into 6C2+ and 6C2- subpopulations. The CD4+CD45RO+6C2+ cells maximally respond to soluble Ag such as tetanus toxoid and provide strong helper function for PWM-driven B cell IgG synthesis. Most interestingly, anti-6C2 was also reactive against activated B cells but not resting B cells; furthermore, this epitope was inducible through activation of resting B cells or B cell line. Biochemical characterization showed that anti-6C2 precipitated two glycoproteins with the relative molecular weights of 180,000 and 95,000 from 125I-surface labeled cell lysate. Sequential immunoprecipitation studies demonstrated that these two glycoproteins were the lymphocyte function-associated antigen (LFA-1) Ag complex (CD11a/18). Significantly, although this antibody did not inhibit cytotoxic killer T cell responses and Ag-induced T cell proliferation as did conventional anti-LFA-1, it did inhibit PWM-driven B cell IgG synthesis. Because 6C2 expression was induced after B cell activation, the above results strongly suggest that the 6C2 molecule may play a role in the interaction of CD4 helper cells and activated B lymphocytes.     

CD2 is expressed by a subpopulation of normal B cells and is frequently present in mature B-cell neoplasms

BACKGROUND: CD2 is expressed by T and natural killer (NK) cells and has been reported in T/NK cell lineage neoplasms as well as in immature B-lymphoblastic and myeloid leukemias. Although CD2+ B-cells have been identified in normal fetal and postnatal thymus, they have not been reported in adults. METHODS: We retrospectively reviewed flow cytometric immunophenotypic data on consecutive low-grade B-cell leukemias and lymphomas to investigate the frequency of CD2 expression. We also reviewed samples from normal healthy donors to determine whether there is a normal CD2+ B-cell population. RESULTS: CD2 expression (partial or complete) was observed in 13 of 83 (16%) chronic lymphocytic leukemias (CLL), 16 of 29 (55%) follicle center lymphomas (FCL), 3 of 12 (25%) hairy cell leukemias (HCL), 0 of 6 mantle cell lymphomas (MCL), 8 of 28 (29%) large cell lymphomas (LCL), and in 0 of 5 marginal zone/mucosa-associated lymphoid tissue lymphomas (MZL/MALT). We determined that 5.74 +/- 2.46% (mean +/- SD) of normal peripheral blood B cells and 6.48 +/- 1.62 % (mean +/- SD) of normal bone marrow B cells coexpress CD2. CONCLUSIONS: CD2 expression in B-cell neoplasia is a more prevalent phenomenon than previously appreciated. Normal CD2+ B-cell populations are observed in adults and may represent the nonmalignant counterpart of CD2+ B-cell neoplasms.     

Cancer dormancy. VII. A regulatory role for CD8+ T cells and IFN-gamma in establishing and maintaining the tumor-dormant state

Dormant tumor cells resistant to ablative cancer therapy represent a significant clinical obstacle due to later relapse. Experimentally, the murine B cell lymphoma (BCL1) is used as a model of tumor dormancy in mice vaccinated with the BCL1 Ig. Here, we used this model to explore the cellular mechanisms underlying dormancy. Our previous studies have demonstrated that T cell-mediated immunity is an important component in the regulation of tumor dormancy because Id-immune T cells adoptively transferred into passively immunized SCID mice challenged with BCL1 cells significantly increased the incidence and duration of the dormant state. We have extended these observations and demonstrate that CD8+, but not CD4+, T cells are required for the maintenance of dormancy in BCL1 Ig-immunized BALB/c mice. In parallel studies, the transfer of Id-immune CD8+ cells, but not Id-immune CD4+ cells, conferred significant protection to SCID mice passively immunized with nonprotective levels of polyclonal anti-Id and then challenged with BCL1 cells. Furthermore, the ability of CD8+ T cells to induce a state of dormancy in passively immunized SCID mice was completely abrogated by treatment with neutralizing alpha-IFN-gamma mAbs in vivo. In vitro studies demonstrated that IFN-gamma alone or in combination with reagents to cross-link the surface Ig induced both cell cycle arrest and apoptosis in a BCL1 cell line. Collectively, these data demonstrate a role for CD8+ T cells via endogenous production of IFN-gamma in collaboration with humoral immunity to both induce and maintain a state of tumor dormancy.     

Phenotypic characterization of thymic prelymphoma cells of B10 mice treated with split-dose irradiation

Using an intrathymic injection assay on B10 Thy-1 congenic mice, it was demonstrated that thymic prelymphoma cells first developed within the thymuses from 4 to 8 days after split-dose irradiation and were detected in more than 63% of the test donor thymuses when examined at 21 and 31 days after irradiation. Moreover, some mice (25%) at 2 mo after split-dose irradiation had already developed thymic lymphomas in their thymuses. To characterize these thymic prelymphoma cells, the thymocytes from B10 Thy-1.1 mice 1 mo after irradiation were stained with anti-CD4 and anti-CD8 mAb and were sorted into four subpopulations. These fractionated cells were injected into the recipient thymuses to examine which subpopulation contained thymic prelymphoma cells. The results indicated that thymic prelymphoma cells existed mainly in CD4- CD8- and CD4- CD8+ thymocyte subpopulations and also in CD4+ CD8+ subpopulation. T cell lymphomas derived from CD4- CD8- prelymphoma cells had mainly CD4- CD8- or CD4- CD8+ phenotypes. T cell lymphomas developed from CD4- CD8+ prelymphoma cells mainly expressed CD4- CD8+ or CD4+ CD8+ phenotype. T cell lymphomas originating from CD4+ CD8+ prelymphoma cells were mainly CD4+ CD8+ but some CD4- CD8+ or CD4+ CD8- cells were also present. These thymic prelymphoma cells were further characterized phenotypically in relation to their expression of the marker defined by the mAb against J11d marker and TL-2 (thymus-leukemia) Ag, which is not expressed on normal thymocytes of B10.Thy-1.2 or B10.Thy-1.1 strain, but appears on the thymocytes of lymphomagenic irradiated mice. The results indicated that the prelymphoma cells existed in J11d+, TL-2+ cells.