Although 13 years have passed since identification of human immunodeficiency virus-1 (HIV-1) as the cause of AIDS, we do not yet know how HIV kills its primary target, the T cell that carries the CD4 antigen. We and others have shown an increase in the percentage of apoptotic cells among circulating CD4+ (and CD8+) T cells of HIV-seropositive individuals and an increase in frequency of apoptosis with disease progression. However, it is not known if this apoptosis occurs in infected or uninfected T cells. We show here, using in situ labelling of lymph nodes from HIV-infected children and SIV-infected macaques, that apoptosis occurs predominantly in bystander cells and not in the productively infected cells themselves. These data have implications for pathogenesis and therapy, namely, arguing that rational drug therapy may involve combination agents targeting viral replication in infected cells and apoptosis of uninfected cells.

Summ~aryDuring human immunodeficiency virus (HIV) infection there is a profound and selective decrease in the CD4 + population of T lymphocytes. The mechanism of this depletion is not understood, as only a small fraction of all CD4 + cells appear to be productively infected with HIV-1 in seropositive individuals. In the present study, crosslinking of bound gp120 on human CD4 + T cells followed by signaling through the T cell receptor for antigen was found to result in activation-dependent cell death by a form of cell suicide termed apoptosis, or programmed cell death. The data indicate that even picomolar concentrations of gp120 prime T cells for activationinduced cell death, suggesting a mechanism for CD4 + T cell depletion in acquired immune deficiency syndrome (AIDS), particularly in the face of concurrent infection and antigenic challenge with other organisms. These results also provide an explanation for the enhancement of infection by certain antibodies against HIV, and for the paradox that HIV appears to cause AIDS after the onset of antiviral immunity.T he immunodeficiency that defines AIDS is due primarily to a progressive decline in the number and function of CD4 + T cells. The mechanism of this decline is debated, though lyric infection of cells targeted by interaction of CD4 with the envelope glycoprotein of the HIV virion, gp120, is an obvious model (1-4), and recent data suggest an apoptotic mechanism of cell death after HIV infection (5). However, previous studies have found that only 1 in 1-10 x 104 PBMC actively express HIV-1 in patients with AIDS (6-10), and immune dysfunction is seen early in infection, before a significant proportion of CD4 + cells has been eliminated (11-15). Thus, it is likely that mechanisms other than direct viral destruction contribute to CD4 + T cell loss and to the anergy associated with CD4 + T cell-dependent immune responses.Mouse splenic T cells pretreated with anti-CD4 antibodies die by apoptosis when stimulated through the oL/~ TCR (16). Apoptosis is an active form of physiologic cell death, requiring RNA and protein synthesis, which is characterized by the activation of endogenous endonucleases that cleave chromatin DNA between nucleosomes (17, 18). Here we report that crosslinking of gp120 on human CD4 + T cells followed by signaling through the TCR results in activation-induced cell death. This cell death has the characteristic features of apoptosis, including the histologic changes of nuclear and cytoplasmic condensation and DNA fragmentation into nucleosome-sized multimers of 200 bp. Our data provide a mechanism for the recent observation that CD4 + T cells from HIV-infected individuals are primed in vivo for suicide by apoptosis, upon TCR activation by both superantigen and MHC class II-restricted antigens (19). Materials and Methodslsola~'on ofCD4 + T Cells. Human T ceils were separated from Ficoll-Hypaque-isolated PBMC by rosetting with 2-aminoethylisothio-uronium bromide hydrobromide (AET)-treated SRBC, as described (20). CD4 + calls were isolated by incu...

Genome-wide association studies (GWASs) have identified hundreds of susceptibility genes, including shared associations across clinically distinct autoimmune diseases. We performed an inverse χ2 meta-analysis across ten pediatric-age-of-onset autoimmune diseases (pAIDs) in a case-control study including more than 6,035 cases and 10,718 shared population-based controls. We identified 27 genome-wide significant loci associated with one or more pAIDs, mapping to in silico–replicated autoimmune-associated genes (including IL2RA) and new candidate loci with established immunoregulatory functions such as ADGRL2, TENM3, ANKRD30A, ADCY7 and CD40LG. The pAID-associated single-nucleotide polymorphisms (SNPs) were functionally enriched for deoxyribonuclease (DNase)-hypersensitivity sites, expression quantitative trait loci (eQTLs), microRNA (miRNA)-binding sites and coding variants. We also identified biologically correlated, pAID-associated candidate gene sets on the basis of immune cell expression profiling and found evidence of genetic sharing. Network and protein-interaction analyses demonstrated converging roles for the signaling pathways of type 1, 2 and 17 helper T cells (TH1, TH2 and TH17), JAK-STAT, interferon and interleukin in multiple autoimmune diseases.

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Objective. To examine the relationship between changes in anti-double-stranded DNA (anti-dsDNA) antibody levels and the risk of renal flare in patients with systemic lupus erythematosus (SLE), using data from 2 randomized, controlled trials.Methods. Analyses were based on 487 patients with SLE and a history of lupus nephritis who had an anti-dsDNA antibody titer >15 IU/ml at baseline, as measured by Farr assay. Results are presented for the combined population of patients, the placebo arms, and the drug treatment arms in which a dsDNA-based bioconjugate (abetimus sodium; LJP 394) was used.Results. Changes in anti-dsDNA antibody levels were inversely correlated with changes in the C3 level (P < 0.0001 in both trials). Cox proportional hazards regression models showed that changes in anti-dsDNA antibody levels correlated with the risk of renal flare. The models predicted that a point estimate of a 50% reduction in anti-dsDNA antibody levels is associated with a 52% reduction (95% confidence interval [95% CI] 26-68%, nominal P ‫؍‬ 0.0007) and a 53% reduction (95% CI 33-69%, nominal P < 0.0001) in the risk of renal flare in the 2 trials, respectively. In the 2 trials, the incidence of renal flare was lower in patients with sustained reductions in anti-dsDNA antibodies (3.0% and 4.1%, respectively) than in patients with stable or increasing antibody levels (21.3% and 20.3%, respectively).Conclusion. Changes in anti-dsDNA antibody levels were directly correlated with the risk of renal flare and inversely correlated with changes in the C3 level. Reducing anti-dsDNA antibody levels may represent a therapeutic objective in SLE patients with lupus nephritis, because it is associated with a reduced risk of renal flare.Anti-double-stranded DNA (anti-dsDNA) antibodies are diagnostic for systemic lupus erythematosus (SLE) (1) and have been implicated in the underlying pathogenesis of SLE renal disease and other disease manifestations (2-7). Immune complexes containing anti-