SummaryTranslocation-associated Notch homologue (TAN-l), a gene originally cloned from the translocation breakpoint of a human T cell leukemia carrying a 9:7(q34.3) translocation, encodes a protein belonging to the Notch/Lin-12/Glp-1 receptor family. These receptors mediate the specification of numerous cell fates during development in invertebrates and vertebrates. The intracellular portion of Notch/TAN-1 contains six ankyrin repeats that are similar to those found in cytoplasmic Ir proteins. IKB proteins are specific inhibitors of nuclear factor (NF)-cd3/Rel transcription factors. Here we show that TAN-1 has functional properties of an Icd3-1ike regulator with specificity for the NF-ed3 p50 subunit. A recombinant polypeptide corresponding to the cytoplasmic portion of TAN-1 (TAN-lc) specifically inhibited the DNA binding ofp50-containing NF-KB complexes. When overexpressed in an appropriate cell line, TAN-1 c prevented KB-dependent transactivation in transient reporter gene assays in a fashion similar to the structurally related protein, Bcl-3. TAN-1 c could activate KB-dependent gene expression by attenuating the inhibitory effect of an excess of p50 hom,odimers. Immunoprecipitation experiments showed that the TAN-1 from a T cell hne is associated with NF-KB containing p50 and p65 subunits. These observations indicate that TAN-1 c may directly engage NF-Id3 transcription factors and modulate nuclear gene expression.

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The expression of B-cell antigens on various cell populations was studied through the use of human alloantisera and with heteroantisera raised to preparations of the alloantigen bearing molecules isolated from B-cell lines. The allo-and hetero-antisera competed with each other in blocking experiments and gave closely parallel results, reacting with normal and leukemic B lymphocytes, monocytes, E-rosette-negative acute lymphatic leukemias, all acute and certain chronic myelogenous leukemias, and a minor population of cells in fetal spleen and liver. These highly immunogenic surface components appeared to comprise the dominant B- cell specific plasma membrane determinants. Neither type of antiserum reacted with any but a minor population of normal or pokeweed-mitogen-transformed T cells, fetal thymic lymphocytes, E-rosette-positive acute lymphatic leukemias, or Sezary-cell leukemia. Through the use of these antisera evidence was obtained that Fc-receptor-bearing Ig-negative lymphocytes were divisible into two groups according to the presence or absence of the B-cell antigens. Both hetero- and allo-antisera blocked binding of immune complexes or antibody-coated ox erythrocytes to Fc receptors on B cells. F(ab')2 fragments of the heteroantibodies strongly inhibited antibody-dependent cell-mediated killing.

The CD4 molecule, which is expressed by a subset of mature human T cells, has been identified as the cellular receptor for the human immunodeficiency virus type I (HIV I)' (1, 2). In searching for the putative region in the HIV I envelope protein that interacts with the CD4 receptor, we postulated that this virus had evolved to mimic the natural ligand of CD4. It was previously established that CD4 plays an auxiliary role during T cell activation, probably by interacting with MHC class II molecules on APCs that also serve as restriction elements for presentation of foreign antigens to the T cell receptors (3-5). Furthermore, results from a study in which chimeric class I/class II molecules bearing L cells were used led us to suspect that the NH2-terminal domain of the MHC class II ,B chain (,B 1 domain) is involved in CD4 binding (5).In this report we describe a computer search comparing the conserved amino acid regions of HLA class 11 a and 0 chains with the amino acid sequences of HIV I proteins . This search identified an homology between two highly conserved sequences in the 0 1 domain of HLA class II molecules and in the gp41 region of HIV I envelope protein.To assess the biological relevance of this homology, peptides from the conserved regions of HIV gp41 and HLA class II were synthesized and tested for their ability to generate antibodies that would recognize the native protein molecules. This report describes the generation of murine mAbs against the gp41-derived peptide and their crossreactivity on native HIV I env as well as on human class II antigens. Moreover, in screening of HIV I-infected individuals, 'Abbreviations used in this paper: AA, amino acids; CSA, chicken serum album; HIV 1, human immunodeficiency virus type I.

BruceUa abortus may be useful as a component of vaccines. This is because it possesses several unique properties as a carrier that enable it to stimulate human B cells even in the relative absence of T cells. Human immunodeficiency virus type 1 proteins conjugated to B. abortus could induce neutralizing antibodies against human immunodeficiency virus type 1. Recently we showed that the characteristics of lipopolysaccharide (LPS) derived from B. abortus are similar to those of the whole bacterium in that the LPS acts as a T-independent type 1 carrier in mice. In this study we wanted to determine whether LPS derived from B. abortus is associated with the adverse effects seen with other bacterial endotoxins. LPS purified from B. abortus by butanol extraction was shown to have <2% (wt/wt) contamination by protein and < 1% (wt/wt) contamination by nucleic acids and to contain 1% (wt/wt) ketodeoxyoctanic acid. Compared with LPS derived from Escherichia coli, B. abortus LPS was 10,000-fold less potent in eliciting fever in rabbits, 268-fold less potent in killing D-galactosamine-sensitized mice, and 1,400-fold and 400-fold less potent in inducing interleukin-1 and tumor necrosis factor alpha production, respectively. These results suggest that B. abortus LPS is much less likely than the LPS from E. coli to evoke endotoxic shock; therefore, it may be feasible to incorporate B. abortus as a component of vaccines.

The role of phospholipid methylation and phospholipase A2 (phosphatide 2-acylhydrolase, EC 3.1.1.4) in natural killer (NK) function by human peripheral blood mononuclear cells was studied. Pretreatment of effector cells with a methyltransferase inhibitor, 3-deazaadenosine, in the presence of homocysteine thiolactone, reduced cytotoxicity in a dose-dependent fashion.This effect was closely associated with inhibition of methylation of lipids but not of nucleic acids or proteins. The suggestion for a role of phospholipid methylation was supported by the observation that the interaction between NK-susceptible tumor targets and peripheral blood mononuclear cells caused increased phospholipid methylation only when susceptible target cells were used. Phospholipase A2 was also implicated in human NK activity. Inhibitors of the enzyme such as tetracaine, mepacrine, Rosenthal's inhibitor, and corticosteroids impaired NK function. Rosenthal's inhibitor was also shown to exert an inhibitory effect on a purified NK-cell population obtained by the isolation oflarge granular lymphocytes on Percoll gradients. Peripheral blood mononuclear cells were also directly shown to display phospholipase A2-like activity, as measured by the decrease in radioactive arachidonate from prelabeled phospholipids, specifically phosphatidylcholine, in effector cells. These data suggest that enhanced phospholipid methylation occurs during the recognition function of NK cells. Consequent activation of phospholipase A2 might be involved in the mechanisms leading to lytic events within the target cell.Transmethylation, the donation of methyl groups to species of RNA, DNA, proteins, carbohydrates, or lipids is necessary for a wide variety of important cellular functions. Recently, two methyl transferases located on the cell membrane have been identified that participate in the synthesis-of phosphatidylcholine from phosphatidylethanolamine, with attendant influences on membrane fluidity and receptor functions (1-3). In the im--mune system, chemotaxis (4-6), histamine release by mast cells and basophils (7,8), mitogen stimulation (9), and cell-mediated lympholysis (10) are among the actions affected by this pathway.The metabolism of glycerophospholipids through the action ofphospholipase A2 (phosphatide 2-acylhydrolase, EC 3.1.1.4), with the resulting liberation of the corresponding lyso-compounds and free fatty acids, has also been implicated in regulatory and effector function in cells of the.immune system (4, 9-11). Particular interest has focused on the accumulation of lysolecithin, a detergent and fusogen, in tumors, which could potentially mediate their lysis.Natural (13). In experiments in which phospholipid metabolism was measured, three to six washes of cells harvested from the interface were done to achieve fewer than two platelets per mononuclear cell. Large granular lymphocytes (LGL) were isolated by Percoll density gradient separation as described (14).Long-term cell lines were grown in suspension culture in medium containing fetal...

THOMASPeripheral blood lymphocytes from patients with systemic lupus erythematosus (SLE) demonstrated significantly less cytotoxicity against two different lymphoblastoid cell lines and one myeloid cell line than peripheral blood lymphocytes from normal individuals. Short-term culture and other attempts to remove interfering immune complexes failed to restore low natural killer (NK) function. Six day culture in fetal calf serum resulted in increased cytotoxicity by mononuclear cells from normal individuals and some SLE patients, but this effect was shown to be dependent on Fc-, not Fc+, effector cells. Suppressor cells were not demonstrable as a cause for decreased NK activity.Systemic lupus erythematosus (SLE) has been associated with numerous immunologic aberrations (I), ranging from abnormalities of antibody formation to defects in cellular immunity. Recently studies in humans and a mouse (NZB) model have found impaired cytotoxic functions as well, notably those involving antibody-dependent cell cytotoxicity (ADCC) (2) and cell-mediated lympholysis (CML) (3,4).Much interest of late has focused on cytotoxic immune functions which take place in the absence of exogenous antibody or known prior sensitization. Socalled natural killing (NK) or spontaneous cell-medi- Studies of effector cells involved in natural cytotoxicity in humans have established their similarity to those participating in antibody-dependent cell cytotoxicity (K cells), principally by the presence of Fc receptors (6,7). In light of previous reports (2) and our own observations (8) documenting impaired ADCC in SLE by immune complexes, antibodies or innate abnormalities of Fc receptor-bearing cell populations, it seemed relevant to study natural killer function as well. We chose to assess NK function in patients with SLE by utilizing radioactive 5'Cr-labeled human lymphoblastoid cell lines (LCL) as targets. The principal problems addressed were: Does natural cytotoxicity reflect pathophysiologic or clinical changes in patients with SLE? What role might the interactions of Fc receptors with antibody or immune complexes play in enhancing or impairing cytotoxic function? MATERIALS AND METHODSPatient selection. Thirty-one SLE patients (25 females, 6 males) were studied. All attended the SLE clinic at the Rockefeller University Hospital. Each patient satisfied the American Rheumatism Association (ARA) clinical criteria for the diagnosis of systemic lupus erythematosus and had strongly positive diagnostic serologies, i.e., antinuclear antibody and anti-DNA antibodies in high titer. Patients were initially classified as having active or inactive disease based on the clinician's subjective evaluation of the presence or absence of systemic symptoms or organ involvement, followed by laboratory documentation of lymphopenia, hypocomplementemia, and elevated erythrocyte sedimentation rate. Healthy laboratory personnel or volunteers served as controls.Cell isolation and culture. Mononuclear cells were isolated from heparinized venous blood on Ficoll-Hypaque gra-

A B S T R A C T Effects of human fibroblast (,) or leukocyte (a) interferon (IFN) on differentiations of a human histiocytic lymphoma-derived cell line (U937) or promyelocytic leukemia-derived cell line (HL-60) were studied. When cultured with ,B-IFN (400-1,000 U/ml), U937 cells showed gross morphologic and microscopic changes consisting of clumping, increased cytoplasmic-to-nuclear ratio, enhanced prominence of cytoplasmic granules, and membrane ruffling. After culture with #l-IFN, the number of U937 cells reactive with B43.4.1 monoclonal antibody, which is specific for human monocytes, natural killer cells, and neutrophils, increased from <10% of U937 cells to 47%. ,B-IFN treatment also enhanced antibody-dependent cellular cytotoxicity against chicken erythrocytes by U937 cells. The same morphologic, phenotypic, and functional changes were also observed when U937 were treated with recombinant or natural a-IFN. The effects of a-IFN were totally abolished by anti-a-IFN serum. In contrast, HL-60, which differentiates toward cells of the monocyte lineage in response to phorbol 12-myristate 13-acetate (based on the above criteria), and toward granulocytes in response to dimethyl sulfoxide, did not differentiate when cultured with a-or ,B-IFN. No consistent relationship between induction of differentiation and changes in phospholipid methylation were observed.