Molecular mimics can induce a nonautoaggressive repertoire that preempts induction of autoimmunity

CD4+ virtual memory: Antigen-inexperienced T cells reside in the naïve, regulatory, and memory T cell compartments at similar frequencies, implications for autoimmunity

It is widely accepted that central and effector memory CD4⁺ T cells originate from naïve T cells after they have encountered their cognate antigen in the setting of appropriate co-stimulation. However, if this were true the diversity of T cell receptor (TCR) sequences within the naïve T cell compartment should be far greater than that of the memory T cell compartment, which is not supported by TCR sequencing data. Here we demonstrate that aged mice with far fewer naïve T cells, respond to the model antigen, hen eggwhite lysozyme (HEL), by utilizing the same TCR sequence as their younger counterparts. CD4⁺ T cell repertoire analysis of highly purified T cell populations from naive animals revealed that the HEL-specific clones displayed effector and central "memory" cell surface phenotypes even prior to having encountered their cognate antigen. Furthermore, HEL-inexperienced CD4⁺ T cells were found to reside within the naïve, regulatory, central memory, and effector memory T cell populations at similar frequencies and the majority of the CD4⁺ T cells within the regulatory and memory populations were unexpanded. These findings support a new paradigm for CD4⁺ T cell maturation in which a specific clone can undergo a differentiation process to exhibit a "memory" or regulatory phenotype without having undergone a clonal expansion event. It also demonstrates that a foreign-specific T cell is just as likely to reside within the regulatory T cell compartment as it would the naïve compartment, arguing against the specificity of the regulatory T cell compartment being skewed towards self-reactive T cell clones. Finally, we demonstrate that the same set of foreign and autoreactive CD4⁺ T cell clones are repetitively generated throughout adulthood. The latter observation argues against T cell-depleting strategies or autologous stem cell transplantation as therapies for autoimmunity-as the immune system has the ability to regenerate pathogenic clones.

Synthesis and cell-based screening of one-bead-one-compound peptide libraries

Combinatorial one-bead-one-compound (OBOC) peptide library screening has proven to be a powerful tool for identification of small molecules, peptides, or peptidomimetics against a variety of specific targets such as cell surface receptors, protein kinases, proteases, and phosphatases. With each bead displaying many copies of a single chemical entity, millions of compounds can be rapidly synthesized and screened with whole-cell binding on-bead functional assays. Here we describe the methodology for the synthesis, screening, and sequence deconvolution of an OBOC peptide library analyzed for affinity to a cancer cell line.

CD4⁺ T cells in chronic autoantigenic stimulation in MGUS, multiple myeloma and Waldenström's macroglobulinemia

Hyperphosphorylated paratarg-7 (pP-7) carrier state is the strongest and most frequent molecular risk factor for MGUS, multiple myeloma (MM) and Waldenström's macroglobulinemia (WM), inherited autosomal-dominantly and, depending on the ethnic background, found in up to one third of patients with MGUS/MM. Since P-7 is the antigenic target of paraproteins that do not distinguish between wtP-7 and pP-7, we investigated CD4(+) T-cell responses in pP-7(+) patients and controls. Peptides spanning amino acids 1-35 or 4-31 containing phosphorylated or nonphosphorylated serine17 were used for stimulation. CD4(+) cells from 9/14 patients (65%) showed a pP-7 specific HLA-DR restricted response. These results demonstrate that pP-7 specific CD4(+) cells can mediate help for pP-7 specific chronic antigenic stimulation of P-7 specific B cells, which might ultimately result in the clonal evolution of a B cell into MGUS/MM/WM producing a P-7 specific paraprotein. Prerequisites for pP-7 specific stimulation of CD4(+) cells appear to be both a pP-7 carrier state and an HLA-DR subtype able to present and recognize pP-7. Our results serve as an explanation for the exclusive autoimmunogenicity of the hyperphosphorylated variant of P-7 and for the different hazard ratios of pP-7 carriers from different ethnic origins to develop MGUS/MM/WM.

Pathophysiology of Autoimmune Bullous Diseases: Nature Versus Nurture

Pemphigus and pemphigoid are the prototypical immunobullous diseases. Although it has been well established that they are caused by deposition of autoreactive antibodies directed against adherence proteins within the skin, the specific genetic and environmental factors leading to development of these diseases continue to be an area of investigation. Herein, we discuss several of the potential environmental triggers that may induce patients to develop immunobullous diseases including medications, viral infections, UV exposure or other radiation injury and dietary factors. In addition, the potential genetic and immunologic mechanisms contributing to the pathogenesis of pemphigus and pemphigoid will be reviewed. The multifactorial nature of these diseases contributes to their complexity and highlights the importance of a detailed personal and family history when caring for these patients.

Mimicry epitope from Ehrlichia canis for interphotoreceptor retinoid-binding protein 201-216 prevents autoimmune uveoretinitis by acting as altered peptide ligand

We report here identification of novel mimicry epitopes for interphotoreceptor retinoid-binding protein (IRBP) 201-216, a candidate ocular antigen that causes experimental autoimmune uveoretinitis (EAU) in A/J mice. One mimicry epitope from Ehrlichia canis (EHC), designated EHC 44-59, induced cross-reactive T cells for IRBP 201-216 capable of producing T helper (Th)1 and Th17 cytokines, but failed to induce EAU in A/J mice. In addition, animals first primed with suboptimal doses of IRBP 201-216 and subsequently immunized with EHC 44-59 did not develop EAU; rather, the mimicry epitope prevented the disease induced by IRBP 201-216. However, alteration in the composition of EHC 44-59 by substituting alanine with valine at position 49, similar to the composition of IRBP 201-216, enabled the mimicry epitope to acquire uveitogenicity. The data provide new insights as to how microbes containing mimicry sequences for retinal antigens can prevent ocular inflammation by acting as naturally occurring altered peptide ligands.

Sercarzian immunology--In memoriam. Eli E. Sercarz, 1934-2009

During his long career as a principal investigator and educator, Eli Sercarz trained over 100 scientists. He is best known for developing hen egg white lysozyme (HEL) as a model antigen for immunologic studies. Working in his model system Eli furthered our understanding of antigen processing and immunologic tolerance. His work established important concepts of how the immune system recognizes antigenic determinants processed from whole protein antigens; specifically he developed the concepts of immunodominance and crypticity. Later in his career he focused more on autoimmunity using a variety of established animal models to develop theories on how T cells can circumvent tolerance induction and how an autoreactive immune response can evolve over time. His theory of "determinant spreading" is one of the cornerstones of our modern understanding of autoimmunity. This review covers Eli's entire scientific career outlining his many seminal discoveries.

T cell clonal expansions detected in patients with primary biliary cirrhosis express CX3CR1

The intrahepatic biliary destruction of primary biliary cirrhosis (PBC) appears secondary to a multi-lineage response that includes autoantibodies, biliary apotopes, and cellular responses. Although there has been considerable effort in defining the role and specificity of anti-mitochondrial autoantibodies, a major challenge has been the characterization of T effector pathways. This difficulty is due in part to the limitation of current technologies for directly isolating and characterizing autoreactive T cells from patients. Herein, we successfully demonstrate a novel technology for characterizing the surface phenotype of T cell oligoclonal expansions directly ex vivo. Using PBC as a prototypic disease we were able to detect clonal T cell expansions in 15/15 patients examined. Although the T cell expansions from different patients expressed different TCRVβ gene segments, the surface phenotype of the cells was the same. The clonal T cell expansions in PBC patients are CX3CR1(+) Fas(+) effector-memory T cells, a finding of particular importance given the known up-regulation of fractalkine on injured biliary epithelial cells (BEC). In contrast to the persistent aberrantly expanded T cells observed in the PBC patients, T cell expansions detected in response to a herpes viral infection were very dynamic and resolved over time. This protocol can be used to characterize T cell expansions in other autoimmune diseases.

Jeffamine derivatized TentaGel beads and poly(dimethylsiloxane) microbead cassettes for ultrahigh-throughput in situ releasable solution-phase cell-based screening of one-bead-one-compound combinatorial small molecule libraries

A method to efficiently immobilize and partition large quantities of microbeads in an array format in microfabricated poly(dimethylsiloxane) (PDMS) cassette for ultrahigh-throughput in situ releasable solution-phase cell-based screening of one-bead-one-compound (OBOC) combinatorial libraries is described. Commercially available Jeffamine triamine T-403 (∼440 Da) was derivatized such that two of its amino groups were protected by Fmoc and the remaining amino group capped with succinic anhydride to generate a carboxyl group. This resulting trifunctional hydrophilic polymer was then sequentially coupled two times to the outer layer of topologically segregated bilayer TentaGel (TG) beads with solid phase peptide synthesis chemistry resulting in beads with increased loading capacity, hydrophilicity, and porosity at the outer layer. We have found that such bead configuration can facilitate ultrahigh-throughput in situ releasable solution-phase screening of OBOC libraries. An encoded releasable OBOC small molecule library was constructed on Jeffamine derivatized TG beads with library compounds tethered to the outer layer via a disulfide linker and coding tags in the interior of the beads. Compound-beads could be efficiently loaded (5-10 min) into a 5 cm diameter Petri dish containing a 10,000-well PDMS microbead cassette, such that over 90% of the microwells were each filled with only one compound-bead. Jurkat T-lymphoid cancer cells suspended in Matrigel were then layered over the microbead cassette to immobilize the compound-beads. After 24 h of incubation at 37 °C, dithiothreitol was added to trigger the release of library compounds. Forty-eight hours later, MTT reporter assay was used to identify regions of reduced cell viability surrounding each positive bead. From a total of about 20,000 beads screened, 3 positive beads were detected and physically isolated for decoding. A strong consensus motif was identified for these three positive compounds. These compounds were resynthesized and found to be cytotoxic (IC(50) 50-150 μM) against two T-lymphoma cell lines and less so against the MDA-MB 231 breast cancer cell line. This novel ultrahigh-throughput OBOC releasable method can potentially be adapted to many existing 96- or 384-well solution-phase cell-based or biochemical assays.