Thursday, August 24, 2006

Type 1 Diabetes: a cure? (in mice)

drj writes: "Type 1 diabetes is the culmination of an immune-mediated destruction of the insulin-secreting beta cells, resulting in a loss of blood sugar regulation (normoglycemia). NOD (non-obese diabetic) mice often suffer a similar disease, perhaps due to a proteasome defect that reduces nuclear factor activation and alters lymphocyte development. Kodama and colleagues here demonstrate the potential of one strategy to cure diabetes - by stopping the immune attack and allowing regeneration from residual beta cells or progenitor cells. While maintaining normoglycemia with a beta cell transplant, they “reeducated” the immune system of diabetic NOD mice by treatment with an immune activator (complete Freund's adjuvant) and repeated infusions of normal (non-NOD) spleen cells. After 6 weeks of twice weekly infusions followed by removal of the beta cell transplant, islet structures and functional beta cells could be found within the NOD pancreas and the mice maintained normoglycemia for over 9 weeks. The authors believe these findings suggest a promising therapy for human diabetes, avoiding the complications of islet transplantation or stem cell culture.
PubMed Kodama et al. Science 302:1223-1227 (2003)
"Islet Regeneration During the Reversal of Autoimmune Diabetes in NOD Mice" Shohta Kodama, Willem K├╝htreiber, Satoshi Fujimura, Elizabeth A. Dale, Denise L. Faustman (posted originally on Jan 17, 2004)

Tuesday, August 22, 2006

Immunity: Statistically different functional CDR3s in mouse

mhc writes "This article relates interesting differences between the VH CDR3 repertoires of mouse and human. A full analysis was performed of the complete Kabat and IMGT antibody databases to arrive at these conclusions. Among them: that compared to the human sequence, the mouse CDR3 is shorter, more hydrophilic, enriched in tyrosine, and less likely to be structurally constrained by proline or intrachain cys-cys bonding. The functional inference is that the mouse repertoire recognizes the antigen universe in a different manner than human, and that the human response can achieve a much greater divergence than does the mouse. The authors suggest that this analysis can serve as a benchmark by which antigen-specific responses can be compared (e.g. is an anti-DNA response more hydrophilic than the universe of anti-self autoantibody responses, or just more hydrophilic than the "average" response as determined from this analysis?)
PubMed Zemlin M, Klinger M, Link J, Zemlin C, Bauer K, Engler JA, Schroeder HW Jr, Kirkham PM. "Expressed murine and human CDR-H3 intervals of equal length exhibit distinct repertoires that differ in their amino acid composition and predicted range of structures." J Mol Biol. 2003 Dec 5;334(4):733-49
(ed.) VH CDR3 = variable heavy (chain immunoglobulin) complement determining region 3. (Originally posted on January 6, 2005)

Autoimmune Diabetes: Gene expression changes little in diabetic mouse

drj writes "More than 20 genes are known to influence the development of type 1 (autoimmune) diabetes in mice and at least this number are thought to contribute to the disease in humans. Using microarrays representing over 39,000 transcripts, Eaves et al. compared mice from closely related lines that do, or do not, develop diabetes. They identified over 400 differentially expressed genes in spleen and thymus tissues and 8 candidates for one particular susceptibility locus (Idd9.1). However, the expectation that the susceptibility (Idd) loci cause large scale differences in gene expression proved to be wrong. Instead, few changes were observed, suggesting that general patterns of gene expression resist change even during the development of a serious autoimmune disease.
To avoid excluding “suggestive” changes, the investigators set the level of significant change at 1 per 20,000 transcripts instead of 1 per 20 arrays (~800,000 transcripts). They identified potential cis-acting changes by examining chromosome locations. For example, the Idd3 region derived from B6 mice protects about 2/3 of NOD mice from diabetes (20-25% vs. 75-80%). However, only 8 transcripts change expression in Idd3B6 mice, all only modestly (19-66%), and none map within the 0.35 cM Idd3 region on chromosome 3."
PubMed Eaves IA, Wicker LS, Ghandour G, Lyons PA, Peterson LB, Todd JA, Glynne RJ., Combining Mouse Congenic Strains and Microarray Gene Expression Analyses to Study a Complex Trait: The NOD Model of Type 1 Diabetes. Genome Res. 2002;12:232-242"

Monday, August 21, 2006

Transplantation: Manipulated dendritic cells are tolerogenic

drj writes, "Immune suppressive drugs enable clinical transplantation, the only therapy for end-stage organ failure, at the cost of reducing patient protection from infections. Ideally, a patient could be made specifically tolerant of a graft without blocking other immune responses. Using a mouse heart transplantation model, Ichim and colleagues suggest several procedures for doing just that, by manipulating certain costimulatory or antigen presenting skills of allogeneic (donor) dendritic cells (DC).

The authors first induced tolerance through means they have established earlier – treatment of recipient mice with blocking antibodies specific for CD45RB and with LF15-0195 (LF), an analogue of the antirejection drug 15-deoxyspergualin. DC recovered from the spleens of mice with long term surviving grafts stimulate allogeneic (donor) T cells to make interleukin (IL)-4 and IL-10 but not interferon-gamma. Next, they identified 4 treatments that produce similar results: (1) Gene transfer and expression of human Fas ligand (FasL) in DC generate “killer DC” that cause apoptosis of allogeneic T cells. (2) Treatment of DC with LF15-0195 blocked activation of the transcription factor NF-kappaB. (3) DC treated with (MHC) class (II) invariant chain peptide (CLIP). (4) Finally, DC treated with short, interfering RNA (siRNA) corresponding to IL-12 blocked its expression and reduced interferon-gamma while increasing IL-4 expression. Each treatment reduced the ability of DC to specifically stimulate allogeneic T cells, suggesting they could be used to establish transplant tolerance. Although the altered DC phenotype resembles those of DC in demonstrably tolerant mice, it will be necessary to test these treatment are able to induce transplant tolerance.
Ichim et al., Prevention of allograft rejection by in vitro generated tolerogenic dendritic cells. Transpl Immunol. 2003;11:295-306
(Originally posted on Dec. 10, 2003)

Immunity: New T cell Regulatory Proteins

Anonymous writes "Chu and colleagues found 33 proteins that decreased T cell activation induced by triggering the T cell antigen receptor (TCR). They screened for increased CD69, a marker of T activation, induced by antibodies to the TCR in Jurkat cells transduced with a retroviral expression library. Although not exhaustive, the screen identified many truncation mutants of expected (Lck, ZAP70, SHP-1, etc.) and surprising (an integrin, Grb7, etc.) proteins. One new gene was identified, a suspected ubiquitin ligase they named TRAC-1 that previously was only an EST. The proteins’ functions were confirmed in primary T cells. As the authors note, the post genome advances will come from assigning functions to proteins. Their approach may help identify proteins in complex signaling systems. PubMed
J. Biol." (Originally posted on October 2, 2003)
Systematic identification of regulatory proteins critical for T-cell activation
Peter Chu, Jorge Pardo, Haoran Zhao, Connie C Li, Erlina Pali, Mary M Shen, Kunbin Qu, Simon X Yu, Betty CB Huang, Peiwen Yu, Esteban S Masuda1, Susan M Molineaux, Frank Kolbinger, Gregorio Aversa, Jan de Vries, Donald G Payan and X Charlene Liao
Journal of Biology 2003 2:21

Cancer: Reducing tolerance of "self" tumors

CarbonBasedUnit writes "Many human tumor antigens are normal (not mutated) “self” proteins, so Rosenberg’s group treated melanoma (skin cancer) patients by immunizing with a melanocyte peptide while blocking CTLA-4, a protein that is thought to mediate immune self-tolerance. One patient was essentially cured and two improved while the other 11 patients showed no improvement. Nine of the 14 patients developed a remarkable variety of autoimmune complications, severe in 6, stopping the trial (all recovered). This paper also clearly establishes CTLA-4, an inducible protein expressed on activated T lymphocytes, as crucial in maintaining self tolerance in humans.
PubMed Entry" (originally posted on August 29, 2003)

Cancer regression and autoimmunity induced by cytotoxic T lymphocyte-associated antigen 4 blockade in patients with metastatic melanoma.
Phan GQ, Yang JC, Sherry RM, Hwu P, Topalian SL, Schwartzentruber DJ, Restifo NP, Haworth LR, Seipp CA, Freezer LJ, Morton KE, Mavroukakis SA, Duray PH, Steinberg SM, Allison JP, Davis TA, Rosenberg SA. PNAS 2003 Jul 8;100(14):8372-7

Cytotoxic T lymphocyte-associated antigen 4 (CTLA-4), also designated CD152
Regulatory T lymphocytes express CD4 and CD25 on their surface.

Friday, August 18, 2006

Autoimmunity: Peptide immunotherapy risk

CarbonBasedUnit writes "Peptide immunization might reduce destructive autoimmunity, such as seen in type I Diabetes or Multiple Sclerosis. However, Pedotti et al. reported that fatal hypersensitivity (anaphylaxis) can result from immunization and challenge with peptides. Mice were immunized with peptides emulsified in incomplete Freund’s adjuvant (oil), a relatively weak immunization protocol, and challenged with peptides in saline. Although first observed with self peptides, anaphylaxis was also observed against a foreign peptide. NOD (non obese diabetic) mice may be particularly sensitive due to defective immunoglobulin receptors (FcgammaRII).PubMed Entry,BMC Full Text"
Severe anaphylactic reactions to glutamic acid decarboxylase (GAD) self peptides in NOD mice that spontaneously develop autoimmune type 1 diabetes mellitus
Rosetta Pedotti*, Maija Sanna*, Mindy Tsai, Jason DeVoss, Lawrence Steinman, Hugh McDevitt and Stephen J Galli
BMC Immunology 2003 4:2 (originally posted in August 22, 2003)
See also: Liu et al. Anti-peptide autoantibodies and fatal anaphylaxis in NOD mice in response to insulin self-peptides B:9-23 and B:13-23 and
Pedotti et al. An unexpected version of horror autotoxicus: anaphylactic shock to a self-peptide

Sunday, August 13, 2006

Transplantation: Timing critical in blocking inducible costimulator

drj writes "Harada et al. report the survival of mouse heart transplants differing at major (MHC) histocompatibility antigens was prolonged by early or late costimulation blockade. ICOS-B7h costimulation was blocked with rat monoclonal antibodies on days 0-6 (early) or days 4-10 (late). For grafts differing at minor histocompatibility antigens, however, early blockade accelerated rejection while late blockade prolonged graft survival. The authors attribute the difference to the frequency of responding T cells (more against MHC, fewer against minor antigens) and also suggest implications for autoimmune disease therapy. These findings raise important considerations for applying immunomodulating therapies. (originally posted on Aug 11, 2003)
PubMed Abstract, Full Text JCI