Delayed matching to sample task 48: assessment of malingering with simulating design.

The results of neuropsychological tests may be distorted by patients who exaggerate cognitive deficits. Eighty-three patients with cognitive deficit [Amnestic Mild Cognitive Impairment (aMCI), n = 53; Alzheimer's disease (AD) dementia, n = 30], 44 healthy older adults (HA), and 30 simulators of AD (s-AD) underwent comprehensive neuropsychological assessment. Receiver Operating Characteristic (ROC) analysis revealed high specificity but low sensitivity of the Delayed Matching to Sample Task (DMS48) in differentiating s-AD from AD dementia (87 and 53%, respectively) and from aMCI (96 and 57%). The sensitivity was considerably increased by using the DMS48/Rey Auditory Verbal Learning Test (RAVLT) ratio (specificity and sensitivity 93% and 93% for AD dementia and 96% and 80% for aMCI). The DMS48 differentiates s-AD from both aMCI and AD dementia with high specificity but low sensitivity. Its predictive value greatly increased when evaluated together with the RAVLT.

Amplification of T cell blastogenic responses in healthy individuals and patients with acquired immunodeficiency syndrome.

Human immunodeficiency virus (HIV) infection is associated with a profound impairment of T cell function. Hence, enhancement of T cell reactivity to viral and bacterial antigens is important in the treatment of patients with AIDS. To develop tools for amplifying T cell reactivity, we have immunized mice with human helper T cell clones and selected monoclonal antibodies (MAbs) that enhance in vitro blastogenic responses. MAb NDA5, which recognizes the leukocyte common antigen CD45, amplifies human T cell responses to mitogens and soluble antigens including HIV-1 glycoprotein (gp)-120 and peptides derived from the HIV-1 gp-120 sequence. In the presence of MAb NDA5, peripheral blood mononuclear cells (PBMC) from healthy, HIV-1-seronegative individual displayed augmented blastogenic responses to HIV-1 gp-120 and to HIV-1 gp-120 synthetic peptides. In vitro memory responses to various vaccines and to alloantigens were also enhanced in cultures with MAb. Similarly, the response of PBMC from AIDS patients to pokeweed mitogen, HIV-1 gp-120, and tetanus toxoid was enhanced with MAb NDA5. The finding that the in vitro immune response of patients with AIDS can be amplified with MAb NDA5, suggests that the in vivo immune response of immunodeficient individuals can also be enhanced.

Establishment of AIDS-related lymphoma cell lines from lymphomatous effusions.

AIDS-related non-Hodgkin lymphomas (AIDS-NHL) are most frequently derived from B cells and include small non-cleaved cell lymphoma (SNCCL) and diffuse large cell lymphoma (DLCL) and less frequently anaplastic large cell lymphoma (ALCL) or body cavity-based lymphoma (BCBL). AIDS-NHL cell lines have proved useful to study AIDS-NHL pathogenesis. In this report, we describe the establishment and molecular characterization of two novel AIDS-NHL cell lines (HBL-4 and HBL-6) derived from lymphomatous effusions. HBL-4 was derived from a patient with SNCCL, whereas HBL-6 was derived from a patient with BCBL. The identity of the cell lines with the original tumor clone was established by immunoglobulin gene rearrangement analysis. Both HBL-4 and HBL-6 carry a monoclonal EBV infection and do not contain HIV. In addition, HBL-6 harbors DNA sequences of the recently identified Kaposi's sarcoma-associated herpesvirus (KSHV), now formally called human herpesvirus 8 (HHV8). Finally, HBL-4, but not HBL-6, harbors a rearranged c-MYC allele, while the BCL-6 gene displayed a germline configurations in both cell lines. These AIDS-NHL cell lines may prove useful in understanding the biologic events contributing to AIDS-NHL development.

Opposite regulation of gene transcription and cell proliferation by c-Myc and Max.

c-Myc and Max are nuclear phosphoproteins capable of forming DNA-binding, homo- and heteropolymeric complexes in vitro and in vivo. Using a transient cotransfection assay involving c-Myc and Max expression vectors and a reporter gene plasmid containing the Myc/Max binding site, we find that Max represses transcription, whereas a significant stimulation is obtained when Max is coexpressed with c-Myc. Analysis of specific mutants indicates that transcriptional activation requires both the c-Myc and the Max dimerization and DNA-binding domains, as well as the c-Myc transactivation function; transcriptional repression by Max requires both DNA binding and dimerization. Analogously, in stably transfected human B-lymphoblastoid cell lines, overexpressed c-Myc and Max synergize to cause malignant transformation, whereas overexpression of Max alone leads to growth inhibition. These results indicate that the c-Myc and Max are transcriptional regulators with the ability to oppositely regulate target-gene expression and cell proliferation, most likely as the result of the opposite effects of heterodimeric c-Myc-Max (positive) versus homodimeric Max (negative) complexes.

Negative autoregulation of c-myc gene expression is inactivated in transformed cells.

Negative feedback regulation of c-myc gene expression has been observed in some, but not all, cell types. In order to demonstrate conclusively the existence of this mechanism and gain insight into the cause of its inactivation, we have directly examined its function in B cells and then investigated its activity in a number of cell types. We demonstrate the existence of negative c-myc autoregulation by showing the rapid, dose dependent and reversible suppression of endogenous c-myc expression in EBV-immortalized B lymphoblastoid cells transfected with a c-myc gene expressed under the control of a heavy metal inducible promoter. Autoregulation occurs at the level of transcriptional initiation and is mediated by at least one stable intermediate or cofactor molecule. The c-myc autoregulatory mechanism was found operative in all (11 of 11) non-tumorigenic cells tested, including normal and immortalized lymphocytes and fibroblasts. However, this mechanism was found to be inactive in all (10 of 10) tumor cell lines derived from a variety of tissues including those carrying normal and oncogenically activated c-myc genes. These data establish the existence of an important regulatory circuit modulating c-myc expression in normal cells and suggest that its inactivation may represent a general regulatory disturbance of transformed cells.

BCL-6 protein is expressed in germinal-center B cells.

Structural alterations of the 5' noncoding region of the BCL-6 gene have been found in 40% of diffuse large cell lymphoma (DLCL) and 5% to 10% of follicular lymphomas (FL), suggesting that deregulated BCL-6 expression may play a role in lymphomagenesis. Nucleotide sequencing of BCL-6 cDNA predicted a protein containing six zinc-finger domains, suggesting that it may function as a transcription factor. Using antisera raised against N- and C-terminal BCL-6 synthetic oligopeptides in immunoprecipitation, immunoblot, and immunocytochemical assays, this study identifies the BCL-6 gene product as a 95-kD nuclear protein. Western blot analysis of human tumor cell lines representative of various hematopoietic lineages/stages of differentiation showed that the BCL-6 protein is predominantly expressed in the B-cell lineage where it was found in mature B cells. Immunohistochemical analysis of normal human lymphoid tissues indicated that BCL-6 expression is topographically restricted to germinal centers including all centroblasts and centrocytes. The BCL-6 protein was also detectable in inter- and intra-follicular CD4+ T cells, but not in other follicular components including mantle-zone B cells, plasma cells, dendritic cells, and macrophages. Immunohistochemical analysis of DLCL and FL biopsy samples showed that the BCL-6 protein is detectable in these tumors independent of the presence of BCL-6 gene rearrangements. These results indicate that the expression of the BCL-6 gene is specifically regulated during B-cell differentiation and suggest a role for BCL-6 in germinal center development or function. Because DLCL derive from germinal-center B cells, deregulated BCL-6 expression may contribute to lymphomagenesis by preventing postgerminal center differentiation.

BCL-6 and the molecular pathogenesis of B-cell lymphoma.

The results presented identify the first genetic lesion associated with DLCL, the most clinically relevant form of NHL. Although no proof yet exists of a role for these lesions in DLCL pathogenesis, the feature of the BCL-6 gene product, its specific pattern of expression in B cells, and the clustering of lesions disrupting its regulatory domain strongly suggest that deregulation of BCL-6 expression may contribute to DLCL development. A more precise definition of the role of BCL-6 in normal and neoplastic B-cell development is the goal of ongoing study of transgenic mice engineered either to express BCL-6 under heterologous promoters or lacking BCL-6 function due to targeted deletions. In addition to contributing to the understanding of DLCL pathogenesis, the identification of BCL-6 lesions may have relevant clinical implications. DLCL represent a heterogeneous group of neoplasms which are treated homogeneously despite the fact that only 50% of patients experience long-term disease-free survival (Schneider et al. 1990). The fact that BCL-6 rearrangements identify biologically and clinically distinct subsets of DLCL suggests that these lesions may be useful as markers in selection of differential therapeutic strategies based on different risk groups. Furthermore, the BCL-6 rearrangements can be used to identify and monitor the malignant clone with sensitive PCR-based techniques. Since clinical remission has been observed in a significant fraction of DLCL cases, these markers may serve as critical tools for sensitive monitoring of minimal residual disease and early diagnosis of relapse (Gribben et al. 1993).