A novel monoclonal antibody specific for human pre-B cell leukemia/lymphoma

'Normal counterparts' of nodal peripheral T-cell lymphoma

Peripheral T-cell lymphomas (PTCL) have been difficult to classify. A homogeneous principle of classification is still lacking, partly because lymph node compartments containing functionally distinct T-cell subsets have not been identified. A correlation to differentiated T-cell subsets, as CD4(+) or CD8(+) cells as well as cytotoxic populations has not revealed clinically meaningful entities. Upon antigen encounter, mature T-cells pass through distinct stages characterized by their surface molecule expression. Naïve T-cells are CD45RA(+)/CD45R0(-)/CD27(+)/CCR7(+), however, after antigen contact CD45RA expression is replaced by CD45R0. They differentiate to central memory cells, which retain CD27 and CCR7, or to effector-memory cells, which loose expression of both molecules depending on the strength of the antigen interaction. Immunohistological analysis of PTCL showed an effector or effector-memory cell phenotype (CD45RA(-)/CD45R0(+)/CD27(-)) for both angioimmunoblastic T-cell lymphoma (AILT) and anaplastic large cell lymphoma (ALCL), but different cytotoxic and activation markers expressed by these tumours. A subset of CD4(+) PTCL-not otherwise specified (PTCL-NOS) may correspond to a central memory cell phenotype (CD45RA(-)/CD45R0(+)/CD27(+)). Thus, a correlation of PTCL to stages of differentiation, rather than to the direction of differentiation, may reveal homogeneous categories. A comparison between the lymphomas and their normal counterparts may contribute to the understanding of the underlying transformation mechanisms.

Identification of the tumor cells in peripheral T-cell lymphomas by combined polymerase chain reaction-based T-cell receptor beta spectrotyping and immunohistological detection with T-cell receptor beta chain variable region segment-specific antibodies

Most nodal peripheral T-cell lymphomas (PTCL) originate from alphabeta-T cells, and they often contain reactive T cells that may hamper immunophenotyping. To specifically identify the neoplastic population in immunohistochemically stained slides, we assessed the heterogeneity of the T-cell receptor beta chain variable region (TCRVbeta). This region contains 65 gene segments, of which only one is expressed after rearrangement. To investigate PTCL, we developed a polymerase chain reaction assay to define the clonally rearranged TCRVbeta segment. Detecting the corresponding epitope with segment-specific antibodies enabled identification of tumor cells among the T cells. The TCRVbeta segment of the tumor cells was defined in 13 of 13 PTCL not otherwise specified and 11 of 13 angioimmunoblastic T-cell lymphomas. Antibodies corresponding to the respective TCRVbeta segment of the tumor were available for seven cases from each group. After applying these antibodies in combination with antibodies against CD3, CD5, CD4, CD8, and cytotoxic molecules, double stains were evaluated by confocal laser scanning microscopy. In 9 of 14 cases, less than 50% of T cells expressed the clonally rearranged TCRVbeta segment. Phenotypes defined in double stains differed from those obtained by conventional immunohistochemistry in 11 of 14 cases. The combination of TCRVbeta polymerase chain reaction and immunohistochemistry may facilitate more reliable detection and characterization of tumor cells in PTCL.