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Background and Objectives. We explored the expression of LCK and BAFF-R (B-cell activating factor receptor) both of which are known to play a role in signaling and apoptosis, in routine tissue biopsies. It was hypothesized that their expression patterns might yield information on apoptosis as it occurs in normal and reactive lymphoid cells, and also be of value for the detection of lymphoma subtypes. Design and Methods. Both molecules were studied in paraffin-embedded tissue sections and cell lines by immunoperoxidase staining, and were also studied by western blotting. Human tonsillar B-cell subsets were analyzed by flow cytometry for LCK expression. Results. LCK was detected for the first time in germinal centers and, at lower levels, in mantle zone B cells. The presence of LCK in B cells was confirmed by western blotting. Cross-linking surface IgM reduced LCK expression whereas cross-linking surface CD40 appeared to have the opposite effect. BAFF-R was present on mantle zone B cells but absent or weakly expressed in germinal center cells. Most lymphomas of germinal center origin (e.g. follicular lymphoma) and also many mantle cell lymphomas, chronic lymphocytic leukemia (CLL) and most T-cell neoplasms expressed LCK. In contrast, BAFF-R was expressed in a variety of B-cell lymphomas, but often absent in grade 3 follicular lymphomas and diffuse large B-cell lymphomas (DLBCL). Both LCK-positive and BAFF-R-positive DLBCL tended to be of germinal-center phenotype. Interpretation and Conclusions. The reciprocal expression pattern of LCK and BAFF-R in germinal center and mantle zone B cells may reflect their opposing roles in apoptosis. Their detection in lymphoma tissue biopsies may therefore be of clinical relevance in predicting response to treatment.

We have previously reported that plasma from patients with anaplastic lymphoma kinase (ALK)-positive lymphoma contains antibodies against the oncogenic kinase NPM-ALK protein characteristic of this disease. We investigated whether this reactivity represents a phenomenon unique to ALK-positive lymphoma by screening plasma from patients with follicular lymphoma for antibodies to BCL-2 protein. Eight out of 10 samples showed such reactivity (and in six cases gave specific staining of BCL-2-transfected cells). As these findings suggest a new biochemical approach to the identification of oncogenic proteins in lymphoma, we investigated whether antibodies present in patients with ALK-positive lymphoma can precipitate NPM-ALK in quantities which should be sufficient for further analysis. We found that plasma samples from all10 patients studied immunoprecipitated NPM-ALK asaprotein visible in silver-stained sodium dodecyl sulphatepolyacrylamide gels. Finally we demonstrated that NPM-ALK could be visualized more clearly if it were immunoprecipitated from extracts of cells in which newly synthesized proteins had been labelled with 35S and then identified by autoradiography. These results suggest a strategy for using patients' autoantibodies to screen for antibodies to other tumour-associated proteins.

Jaw1, also known as lymphoid-restricted membrane protein (LRMP), is an endoplasmic reticulum-associated protein. High levels of Jaw1/LRMP mRNA have been found in germinal centre B-cells and in diffuse large B-cell lymphomas of 'germinal centre' subtype. This paper documents Jaw1/LRMP expression at the protein level in human tissues by immunohistochemical and western blotting analysis using an antibody reactive with paraffin-embedded tissues. Jaw1/LRMP was highly expressed in germinal centre B-cells (in keeping with gene expression data), in 'monocytoid B-cells', and in splenic marginal zone B-cells. It was absent, or present at only low levels, in mature T-cells, although cortical thymocytes were weakly positive. Among lymphoid neoplasms, Jaw1/LRMP was found in germinal centre-derived lymphomas (follicle centre lymphoma, Burkitt's lymphoma, lymphocyte-predominant Hodgkin's disease) but not in T-cell neoplasms (with the exception of a single T lymphoblastic lymphoma). Classical Hodgkin's disease and myeloma lacked Jaw1/LRMP but many cases of chronic lymphocytic leukaemia (but not mantle zone lymphoma) were Jaw1/LRMP-positive. Approximately half of the marginal zone lymphomas were Jaw1/LRMP-positive. In diffuse large B-cell lymphomas, Jaw1/LRMP was found in three-quarters (24/32) of the cases classified phenotypically as being of 'germinal centre' type, but it was also expressed in almost half (13/28) of the 'non-germinal centre' cases. A similar proportion of 'non-germinal centre' cases were positive for the protein products of two other genes expressed highly in germinal centre cells (HGAL/GCET2 and PAG). The fact that all three of these proteins are expressed in a significant proportion of diffuse large B-cell lymphomas assigned to the 'non-germinal centre' category indicates that the immunophenotypic categorization of diffuse large B-cell lymphoma according to cellular origin may be more complicated than currently understood. Finally, the expression of Jaw1/LRMP in other types of lymphoma and in non-lymphoid tissues/tumours may be of interest in differential diagnosis and research.

Transmembrane adaptor proteins (of which 7 have been identified so far) are involved in receptor signaling in immune cells. They have only a short extracellular region, with most of the molecule comprising a substantial intracytoplasmic region carrying multiple tyrosine residues that can be phosphorylated by Src- or Syk-family kinases. In this paper, we report an immunohistologic study of 6 of these molecules in normal and neoplastic human tissue sections and show that they are restricted to subpopulations of lymphoid cells, being present in either T cells (LAT, LIME, and TRIM), B cells (NTAL), or subsets of both cell types (PAG and SIT). Their expression in neoplastic lymphoid cells broadly reflects that of normal lymphoid tissue, including the positivity of plasma cells and myeloma/plasmacytoma for LIME, NTAL, PAG, and SIT. However, this study also revealed some reactions that may be of diagnostic/prognostic value. For example, lymphocytic lymphoma and mantle-cell lymphoma showed similar profiles but differed clearly from follicle-center lymphoma, whereas PAG tended to be selectively expressed in germinal center-derived subsets of diffuse large B-cell lymphoma. These molecules represent a potentially important addition to the panel of immunophenotypic markers detectable in routine biopsies that can be used in hematopathologic studies.

Stimulation of lymphoid cells via their surface receptors triggers signalling pathways that terminate in the nucleus, where they induce alterations in gene transcription. Nuclear factor of activated T cells (NFAT) transcription factors, involved in a major Ca2+-dependent signalling pathway, normally reside in the cytoplasm but re-locate to the nucleus when activation of the pathway (e.g. following ligation of antigen receptors) leads to their dephosphorylation. This study found that one member of the NFAT family (NFATc1/NFAT2) can be detected in routine biopsy samples, where it is seen in essentially all lymphoid cells, but is absent from the great majority of non-haematopoietic cells. An immunohistological evaluation of NFATc1 in almost 300 lymphomas showed that most neoplastic lymphoid cells also express NFATc1 as a cytoplasmic constituent, although it is absent in classical Hodgkin's disease and plasma cell proliferations. Of particular interest was the finding that NFATc1 was relocated to the nucleus in a minority of lymphoid neoplasms (usually diffuse large B-cell lymphomas or Burkitt lymphoma), presumably reflecting activation of the NFAT pathway. It would be of interest to correlate this feature with patterns of gene expression and also with prognosis, since it may identify a subset of human lymphoma that is distinct in its molecular and clinical features.