Blebs and Apoptotic Bodies Are B Cell Autoantigens

Abstract

Mounting evidence suggests that systemic lupus erythematosus autoantigens are derived from apoptotic cells. To characterize the potential interactions between apoptotic cells and B cells, the D56R/S76R variant of 3H9, a murine autoantibody that binds to DNA, chromatin, and anionic phospholipids, was compared with DNA4/1, a human anti-DNA autoantibody. Flow cytometry revealed that only D56R/S76R bound to Jurkat cells treated with either of three distinct proapoptotic stimuli, Ab binding was dependent on caspase activity, and immunoreactivity developed subsequent to annexin V binding. Confocal microscopy established a structural basis for the distinct kinetics of binding. D56R/S76R preferentially bound to membrane blebs of apoptotic cells, whereas annexin V binding did not require blebs. Inhibition of ROCK I kinase, an enzyme that stimulates nuclear fragmentation and fragment distribution into blebs, significantly reduced Ab binding. Because members of the collectin and pentraxin families of serum proteins bind to blebs on apoptotic cells and assist in the clearance of cellular remains, our results suggest that Abs to blebs could affect the recognition of apoptotic cells by cells of the innate immune system and thus modify tolerance to nuclear Ags.

Anti-idiotype-mediated epitope spreading and diminished phagocytosis by a human monoclonal antibody recognizing late-stage apoptotic cells

“…The kinetic parallels between antibody binding and PI recognition, as well as their colocalization on the apoptotic cell surface, is expected, since degraded nucleosomal material is also similarly targeted. 23 The ubiquitous nature of the antigens recognized by the antibody is consistent with the conserved nature of the apoptotic process, and the commonality of biochemical pathways of death that are known to occur, irrespective of cell lineage. Ro52 and Ro60, the molecules recognized by RN86, are RNPs of unknown function in higher organisms.…”

“…22 Apoptotic cell specific molecular patterns (ACAMPs), comprising prominent autoantigens (such as DNA, histones and the ribonucleoprotiens Ro and La), appear upon membrane blebs in advance of cellular lysis and are readily accessible by specific autoreactive antibodies. 23 These appear to segregate into two different populations on the cell surface. Large apoptotic bodies arise from condensed fragmented nuclei and contain nucleosomes, Ro and La and snRNPs, whereas small blebs contain fragmented endoplasmic reticulum (ER) and ribosomal antigens, along with Ro.…”

Exploiting death: apoptotic immunity in microbial pathogenesis

“…Additional transcriptional and other responses (e.g., the induction of TGFβ expression 13 ; Pattabiraman et al, unpublished Arg-II 73,75 ; Pattabiraman et al, unpublished delineated in Figure 1, and the glycolytic enzyme molecules that are externalized apoptotically are indicated. These glycolytic enzyme molecules exist among a surprisingly extensive array of cellular components, representing autoantigens, that are exposed on the surface of apoptotic cells 25 it is likely that the absence of autoimmune reactivity normally is established and maintained through IAI. 3 Biochemical analyses indicate that the externalized glycolytic enzyme molecules, including α-enolase and GAPDH, exist as peripheral membrane proteins in multimeric complexes (Palasiewicz, Pattabiraman, and Ucker, unpublished data).…”

Pathogenic implications for autoantibodies against C-reactive protein and other acute phase proteins

“…Interestingly, many of the nuclear antigens to which CRP binds are the same as those targeted by antinuclear antibodies (ANA) seen in sera from patients with systemic lupus erythematosus (SLE) and other systemic inflammatory rheumatic diseases [56,57]. It is conceivable that CRP, by FcR-mediated uptake in phagocytes, facilitates the clearance of circulating nucleosomes and apoptotic blebs on which nuclear antigens are exposed [55, 58,59], thereby limiting the contact of these autoantigens with the adaptive immune system. In an inflammatory microenvironment with acidic conditions, native CRP dissociates into CRP monomers, which bind to IgG-containing immune complexes (ICs) [60] and to FcRIII [47].…”

“…Some of these blebs are shed as apoptotic bodies on which nuclear autoantigens (e.g. nucleosomes, Ro/SS-A, La/SS-B and Sm) are exposed and may in turn become available to professional antigen-presenting cells [58,108]. Interestingly, monocytoid dendritic cells but not macrophages efficiently present antigens derived from apoptotic cells to cytotoxic T cells [109].…”