Detection of LIM domain only 2 (LMO2) in normal human tissues and haematopoietic and non-haematopoietic tumours using a newly developed rabbit monoclonal antibody.

Aims:  We describe a new rabbit monoclonal antibody, raised against a fixation-resistant epitope of the transcription regulator LIM domain only 2 (LMO2). Methods and results:  Lymphoma cell lines and a large series of normal and neoplastic samples were investigated by Western blot and immunohistochemistry. The antibody detected nuclear positivity for the protein, with the exception of a proportion of classical Hodgkin lymphomas (HLs), peripheral T cell lymphomas (PTCLs) and solid tumours that showed granular cytoplasmic staining. In normal lympho-haematopoietic tissues, LMO2 was expressed at different intensities by CD34(+) blasts, haematopoietic precursors, germinal centre (GC), mantle and splenic marginal zone B cells. While reactive with only scattered elements in the thymus and nine of 237 PTCLs, the antibody stained 31 of 39 T-acute lymphoblastic lymphoma/leukaemias (T-ALLs) and the T-ALL-derived human leukaemic cell line, CCRF-CEM. LMO2 was found in 88% of B-acute lymphoblastic lymphoma/leukaemias (B-ALLs), 5% chronic lymphocytic leukaemias (CLLs) and 14%, 57% and 41% of mantle, follicular and Burkitt lymphomas, respectively. In the setting of diffuse large B cell lymphomas (DLBCLs), LMO2-positivity was related strongly to a GC phenotype. LMO2 was found in 83% primary mediastinal large B cell lymphomas (PMBLs) and 100% nodular lymphocyte predominant Hodgkin lymphomas (NLPHLs), whereas only 10% of classical HLs were stained. Acute and chronic myeloid leukaemias were usually positive. Conclusions:  The new anti-LMO2 antibody can be applied confidently to routine sections, contributing to the differential diagnosis of several lymphoma subtypes, subtyping of DLBCLs and potential development of innovative therapies.