Biomedical subjects

R Korngold

Publications and source records attributed to R Korngold.

At least 37 records · Page 2Linked to original sources

PubMed1997

Immunodominant CD4+ T cell receptor Vbeta repertoires involved in graft-versus-host disease responses to minor histocompatibility antigens.

In vitro CTL responses to multiple minor histocompatibility Ags (miHA) are governed by immunodominance as demonstrated in the C57BL/6By (B6) anti-BALB.B strain combination. Immunodominance was also demonstrated to be operative in graft-vs-host disease (GVHD) responses against BALB.B-derived miHA following transplantation of B6 T cells into irradiated recipients of both the BALB.B and CXB recombinant inbred strains. The hierarchy of in vivo and in vitro T cell responses to miHA differed. GVHD did not develop in CXBG and CXBK mice, which express immunodominant miHA for CTL generation, whereas disease occurred in the BALB.B, CXBE, CXBI, and CXBJ mouse strains. Previous results demonstrated that B6 CD4+ T cells provide helper function for CD8+ T cells involved in GVHD responses in the BALB.B, CXBE, and CXBI strains. CD4+ T cells alone were mediators of GVHD in all strains except CXBE. This study analyzed the TCR Vbeta repertoires of CD4+ thoracic duct lymphocytes (TDL) collected during the initial stages of GVHD in the B6-->BALB.B and B6-->CXBE strain combinations. Positively selected CD4+ TDL from the B6-->BALB.B (B6(+BALB.B)) combination exhibited marked expansion in the TCR Vbeta6+ and Vbeta8.1/8.2+ families, as well as smaller increases in the Vbeta7 and Vbeta9 families. CD4+ TDL from the B6-->CXBE (B6(+CXBE)) combination displayed expansions in only the Vbeta7+ and Vbeta9+ families. These data suggest that B6 CD4+ T cells can recognize a limited number of immunodominant miHA during GVHD induction and that in both BALB.B and CXBE recipients, the TCR Vbeta repertoires partially overlap.

Animals↗

PubMed1997

Bioactive peptide design based on protein surface epitopes. A cyclic heptapeptide mimics CD4 domain 1 CC' loop and inhibits CD4 biological function.

The interaction between CD4 and major histocompatibility complex class II proteins provides a critical co-receptor function for the activation of CD4(+) T cells implicated in the pathogenesis of a number of autoimmune diseases and transplantation responses. A small synthetic cyclic heptapeptide was designed and shown by high resolution NMR spectroscopy to closely mimic the CD4 domain 1 CC' surface loop. This peptide effectively blocked stable CD4-major histocompatibility complex class II interaction, possessed significant immunosuppressive activity in vitro and in vivo, and strongly resisted proteolytic degradation. These results demonstrate the therapeutic potential of this peptide as a novel immunosuppressive agent and suggest a general strategy of drug design by using small conformationally constrained peptide mimics of protein surface epitopes to inhibit protein interactions and biological functions.

Amino Acid Sequence↗

PubMed1997

A synthetic CD4-CDR3 peptide analog enhances bone marrow engraftment across major histocompatibility barriers.

The efficacy of a synthetic peptide analog mimicking the CDR3-D1 domain of the CD4 molecule was investigated in murine models of allogeneic bone marrow engraftment after transplantation across major histocompatibility complex (MHC) barriers. A single dose of a CD4-CDR3 peptide analog was administered at the time of marrow transplantation to three different allogeneic mouse strain combinations after appropriate sublethal total body irradiation: (1) B10.BR --> C57BL/6J (B6), a full allogeneic MHC difference; (2) (B6xDBA/2)F1 --> (B6xCBA)F1, a haploidentical MHC combination; and (3) B6.C-H2bm12 --> B6-Ly5.2, involving only a MHC class II difference. Donor-host chimerism was assessed after 1 and 2 months posttransplantation by flow cytometric analysis of spleen and/or lymph node cells. Peptide-treated animals in all three strain combinations exhibited significantly enhanced donor lymphoid engraftment, which was similarly reflected in the total lymphocyte compartment and its T-cell (CD4+, CD8+) and B-cell subsets. In addition, peptide-treated mice in the haploidentical and MHC class II-mismatched strain combinations exhibited prolonged tolerance of both donor and syngeneic host-type tail skin grafts while rejecting third-party allogeneic grafts, thus supporting the reconstitution of immunocompetence in these chimeras. Lymphocytes from the peptide-treated haploidentical chimeric mice also displayed donor-specific tolerance upon stimulation in a one-way mixed lymphocyte reaction. In a 6-day colony-forming unit-granulocyte-macrophage (CFU-GM) assay to quantitate the level of hematopoietic cell engraftment in both the haploidentical and class II-disparate strain combinations, bone marrow cells from the peptide-treated mice exhibited significant increases in CFU-GM compared with the saline-treated control groups. Finally, early multiple treatments with the peptide after transplantation significantly enhanced donor chimerism in donor-presensitized recipient mice across the MHC class II barrier and proved to be significantly more effective than anti-CD4 monoclonal antibody treatment. These results indicate that the structure-based CD4-CDR3 peptide analog may represent a valuable approach to the inhibition of graft rejection after MHC-mismatched bone marrow transplantation.

Animals↗

PubMed1997

A computer screening approach to immunoglobulin superfamily structures and interactions: discovery of small non-peptidic CD4 inhibitors as novel immunotherapeutics.

The interaction between CD4 and major histocompatibility complex (MHC) class II proteins is critical for the activation of CD4+ T cells, which are involved in transplantation reactions and a number of autoimmune diseases. In this study we have identified a CD4 surface pocket as a functional epitope implicated in CD4-MHC class II interaction and T-cell activation. A computer-based strategy has been used to screen approximately 150,000 non-peptidic organic compounds in a molecular data base and to identify a group of compounds as ligands of the proposed CD4 surface pocket. These small organic compounds have been shown to specifically block stable CD4-MHC class II binding, and exhibit significant inhibition of immune responses in animal models of autoimmune disease and allograft transplant rejection, suggesting their potential as novel immunosuppressants. This structure-based computer screening approach may have general implications for studying many immunoglobulin-like structures and interactions that share similar structural features. Furthermore, the results from this study have demonstrated that the rational design of small non-peptidic inhibitors of large protein-protein interfaces may indeed be an achievable goal.

Animals↗

PubMed1997

Blockade of CD40 ligand-CD40 interaction impairs CD4+ T cell-mediated alloreactivity by inhibiting mature donor T cell expansion and function after bone marrow transplantation.

Alloreactive T cells require costimulatory signals via CD40 ligand (CD40L). The tissue-destructive properties of allogeneic CD4+ but not CD8+ T cells were inhibited by anti-CD40L mAb. Fewer CD4+ thoracic duct lymphocytes (TDL) were obtained in mAb-treated recipients. Kinetic studies revealed that CD4+ T cell expansion was reduced or delayed which may account, in part, for the partial graft-vs-host disease protective effect of anti-CD40L mAb. TDL were found to have diminished anti-host-specific proliferative responses. The frequency of donor TDL and splenocytes that expressed the Th1 cytokines IL-2, IL-12 p40, and IFN-gamma mRNA was markedly diminished in mAb-treated recipients, demonstrating that Th1-driven alloresponses were susceptible to CD40L targeting. Perforin mRNA-expressing T cells were undetectable in mAb-treated recipients, consistent with reduced in vivo lethality after the adoptive transfer of allogeneic CD4+ T cells. Similar findings were observed in both B cell-replete or -deficient recipients, indicating that allogeneic T cell expansion and priming can be sustained by a non-B cell, CD40+ host cell population. Mice receiving CD40L-deficient allogeneic CD4+ T cells had survival rates comparable to the rates of those given anti-CD40L mAb treatment. Because anti-CD40L mAb also was found to prevent host anti-donor-mediated marrow allograft rejection, in vivo blockade of CD40L-CD40 interactions may provide a highly beneficial approach to improving the outcome of allogeneic bone marrow transplantation.

Animals↗

PubMed1997

Immunoglobulin superfamily proteins: structure, mechanisms, and drug discovery.

We review the recent progress made in our laboratories in structure-based drug design targeting proteins of the immunoglobulin superfamily (IgSF). We will focus on the CD4 protein, which is involved in T cell function, as a specific example of how the general concept and methodologies can be applied. Recent studies of CD4 structure and function have revealed new insight into possible mechanisms for CD4 self-association and its role in binding to major histocompatibility complex (MHC) class II molecules and initiation of T cell activation. This has led to the formulation of a hypothetical model of co-oligomerization of CD4, MHC class II, and T cell receptor (TCR). Such a basic understanding of CD4 structure and mechanisms has aided the development of a new generation of potential immunotherapeutics targeting specific CD4 surface functional sites. The design and discovery of small molecular inhibitors of CD4 and other IgSF proteins, in peptide, peptidomimetic, and nonpeptidic organic forms have opened new avenues for chemical research in which peptide, organic, and more recently combinatorial chemistry techniques can be used to further develop these promising lead analogs into a new generation of effective pharmaceuticals.

Animals↗

PubMed1997

Experimental induction and ultrastructural characterization of apoptosis in murine acute cutaneous graft-versus-host disease.

The skin is a primary target organ in acute graft-versus-host disease (GVHD). Recent results suggest that keratinocytes may undergo apoptosis in acute GVHD, although sequential structural evidence supporting this concept is lacking. The present study was undertaken to document and characterize apoptosis, confirmed by endonuclease-mediated DNA fragmentation, in experimental acute GVHD via sequential analysis of ultrastructure. Furthermore, we sought to define whether apoptosis is effector cell-dependent or- independent, and to document cell types responsible for the scavenging of apoptotic cells. Acute GVHD was produced across minor histocompatibility loci using appropriately matched murine strains and highly purified preparations of donor CD4+ and CD8+ T-cell subsets. Transmission electron microscopy was correlated with in situ labeling of double-stranded DNA breaks by the TUNEL (terminal uridine deoxynucleotidyl transferase end ligation) technique. Apoptotic cells were observed in all groups receiving T cells. Although most apoptotic cells were found in apposition with effector lymphocytes, a minority of apoptotic cells were detected at early time-points prior to lymphocytic infiltration. Heterogeneous cells, including macrophages, lymphocytes, Langerhans cells and keratinocytes were involved in scavenging putative target cells undergoing apoptosis. This study confirms the final pathway of target cell injury in acute GVHD to be apoptosis. In acute GVHD, apoptosis can be induced in the presence or absence of local effector cell influx, suggesting at least two mechanisms for the induction of epidermal target cell injury.

Acute Disease↗

PubMed1997

Recent advances in graft-versus-host disease (GVHD) prevention.

In the 1970s and 1980s, GVHD prevention approaches were limited in number. Recent advances in our understanding of the requirements for T-cell immune responses and for basic mechanism(s) involved in GVHD pathophysiology have led to exciting new strategies for GVHD prevention. This review focuses upon recent developments in GVHD prevention generated over the past 5 years. We have selected five different types of strategies to highlight including: 1) the in vivo targeting of GVHD-reactive T cells using either intact and F(ab')2 fragments of monoclonal antibodies directed against T-cell-surface determinants or immunotoxins which consist of antibodies linked to toxins, 2) a comparison of the in vivo immunosuppressive effects of FK506 and rapamycin on T-cell signaling, 3) the inhibition of T-cell activation through blockade of costimulatory or adhesogenic signals, 4) shifting the balance between acute GVHD-inducing T-helper-type 1 (Th1) T cells to anti-inflammatory T-helper-type 2 (Th2)-type T cells, and 5) the regulation of alloreactive T-cell activation by treatment with peptide analogs which affect either TCR/MHC, CD4/MHC class II, or CD8/MHC class I interactions. Collectively, these approaches are illustratrative of the progress made in extending our GVHD prevention armamentarium.

Animals↗

PubMed1997

Inter-strain graft-vs.-host disease T-cell responses to immunodominant minor histocompatibility antigens.

Immunodominance affects the in vitro generation of cytotoxic T lymphocytes (CTL) specific for minor histocompatibility antigens (miHA), as exemplified in the C57BL/6By (B6) anti-BALB.B H2b-matched strain combination. Despite the potential of responding to numerous individual miHA on BALB.B antigen presenting cells, the focus of the CTL response is largely directed to only a limited number of target antigens. These miHA are differentially expressed by the CXBE, CXBG, CXBI, CXBJ, and CXBK recombinant inbred (RI) strains, all of which also express the H2b MHC haplotype. Immunodominance also plays a role in the development of lethal graft-vs.-host disease (GVHD) directed to miHA, by which B6 T cells were transplanted along with T-cell depleted bone marrow to irradiated (825 cGy) recipients of either the BALB.B or CXB RI strains. The hierarchy of immunodominance differed in GVHD from that predicted from the in vitro CTL studies; i.e., GVHD was observed in BALB.B, CXBE, CXBI, and CXBJ recipients, but not in CXBG and CXBK recipients, despite the latter two strains expressing immunodominant antigens for CTL generation. Interpretation of these results was complicated by the finding that potent GVHD could be obtained with the transfer of CXBE T cells and ATBM to irradiated CXBG recipients. To clarify the scope of the inter-strain immunodominant interactions involved in GVHD in these strain combinations and to estimate the minimum number of miHA that could be responsible for GVHD, a full panel of GVHD responses was analyzed. The GVHD potential was evaluated for donor T cells derived from both parental RI strains as well as for (B6 x RI)F1 hybrids to restrict responses to only those miHA originating from BALB.B origin. The results were consistent with the minimal involvement of two distinct immunodominant miHA in the B6-->BALB.B lethal GVHD response. One immunodominant miHA (GVH-1) appeared to be shared by the CXBE, CXBI, and CXBJ RI strains, while the second antigen (GVH-2) was uniquely expressed by the parental BALB.B strain.

Animals↗

PubMed1997

Peptide analogs that inhibit IgE-Fc epsilon RI alpha interactions ameliorate the development of lethal graft-versus-host disease.

Significant increases in serum levels of IgE have often been observed in allogeneic bone marrow transplantation patients and have generally been thought to be diagnostic of graft-versus-host disease (GVHD), rather than an agent involved in the pathogenesis of the disease. Experimental murine GVHD models have also indicated associations of hyper-IgE activity, yet the role of IgE in GVHD pathogenesis has never been tested directly. In the current study, we have tried to address this issue by using recently developed peptide analog antagonists for the interaction of IgE with the Fc epsilon RI receptor, which is necessary for triggering mast cells and other cell types when cross-linked by antigens. A synthetic cyclized 13-amino acid peptide was previously designed from the modeled C-C' loop region of the Fc epsilon RI alpha-chain and was found to act as a competitive inhibitor of IgE-Fc epsilon RI alpha binding. The peptide was generated in two forms, a cyclic L-(L-IgEtide) and retro D-amino acid composition (rDIgEtide), the latter to increase resistance to protease degradation for in vivo applications. These two inhibitor peptides were then used to test the hypothesis that IgE could be involved in the pathogenesis of acute GVHD, in the B10.D2-->DBA/2 (900 cGy) strain combination, with GVHD directed to minor histocompatibility antigens. Both peptides demonstrated significant inhibition of the development of lethal GVHD, supporting the involvement of IgE at some level of disease pathogenesis.

Animals↗

PubMed1996

Infusion of anti-B7.1 (CD80) and anti-B7.2 (CD86) monoclonal antibodies inhibits murine graft-versus-host disease lethality in part via direct effects on CD4+ and CD8+ T cells.

Efficient T cell proliferation requires costimulation via CD28/B7 or other pathways. Graft-vs-host disease (GVHD) is caused by activated donor T cells. We have found that the infusion of anti-B7.1 (CD80) + anti-B7.2 (CD86) mAb is effective in eliminating GVHD lethality induced by either CD8+ or CD4+ T cells. Donor CD4+ and CD8+ T cell expansion was inhibited by almost 100-fold as measured by enumerating thoracic duct lymphocytes (TDL) obtained early post-transplant. TDL retained anti-host responsiveness indicating that not all T cells were anergic. Although anti-CD80 or anti-CD86 mAb individually were ineffective in preventing CD8+ T cell GVHD lethality, each mAb was partially effective in CD4+ T cell-mediated GVHD. Because CD80 expression was found to be up-regulated on donor CD4+ TDL post-transplant, the GVHD capacity of donor CD4+ T cells deficient in CD80 was tested and found to be reduced similarly to that seen with anti-CD80 mAb. These studies demonstrate that anti-CD80 + anti-CD86 mAb infusion is effective in preventing GVHD lethality by inhibiting donor CD4+ or CD8+ T cell expansion and provide the first evidence that CD80 expression on donor T cells is critical for optimal GVHD lethality.

Animals↗

PubMed1996

A CD4-CDR3 peptide analog inhibits both primary and secondary autoreactive CD4+ T cell responses in experimental allergic encephalomyelitis.

A structure-based design approach was used to develop a cyclized peptide analog of the murine CD4-CDR3-like region as a potential inhibitor of autoimmune CD4+ T cells responsible for the pathogenesis of experimental allergic encephalomyelitis (EAE). Our results indicate that this peptide, referred to as rD-mPGPtide, is able to significantly inhibit the clinical and pathologic symptoms of EAE in the SJL mouse model when administered on day 12 of induction. The optimum effective dosage range for the peptide, injected i.v., was between 0.125 and 0.5 mg and dosages of as high as 5 mg had no observable toxic effects. Treated mice had normal levels of lymphocytes less than 2 wk later and exhibited normal in vitro primary responses to alloantigen and secondary responses to keyhole limpet hemocyanin Ag. The specificity of the rD-mPGPtide treatment for autoreactive T cells was demonstrated by inhibiting proteolipid protein (p139-151)-induced EAE and finding that the lymph node T cells from these mice had suppressed responses to this Ag, but normal responses to alloantigen or other nominal Ag. Importantly, rD-mPGPtide was found to be effective on secondary T cell responses in an EAE rechallenge situation and was able to establish conditions for long-term resistance to further Ag exposure. Analysis of the cytokine profile of responding T cells during late effector stages of disease revealed that the levels of IFN-gamma and IL-4 are significantly reduced in rD-mPGPtide-treated mice. These results strongly suggest that the administration of a CD4-CDR3 peptide analog is an effective therapeutic approach for the inhibition of the CD4+ T cell-mediated autoimmune response in EAE.

Amino Acid Sequence↗

PubMed1996

Inhibitory effect of a CD4-CDR3 peptide analog on graft-versus-host disease across a major histocompatibility complex-haploidentical barrier.

A structure-based designed peptide has been engineered to exhibit the same molecular surface as a portion of the CDR3-like region in domain 1 of the murine CD4 molecule. Earlier in vitro experiments indicated that this analog, known as rD-mPGPtide, inhibited T-cell proliferation in mixed lymphocyte reactions and blocked activation of both normal CD4+ T cells and T-cell lines after T-cell receptor triggering. In addition, rD-mPGPtide proved to be a potent inhibitor in vivo of CD4+ T-cell-mediated experimental allergic encephalomyelitis disease in the SJL mouse model. In this current report, we have evaluated the potential of rD-mPGPtide for suppressing the development of graft-versus-host disease (GVHD) in an irradiated major histocompatibility complex (MHC)-haploidentical murine bone marrow transplantation (BMT) model [(B6 x DBA/2)F1-->(B6 x CBA)F1 (950 cGy)]. Our results indicated that early administration of rD-mPGPtide was effective in the inhibition of alloreactive responses of the donor T cells against the host and thus delayed or prevented the onset of GVHD. The median survival time of animals treated with rD-mPGPtide was enhanced as much as four-fold with as little as a single dose of peptide at the time of transplant. Decreased alloreactivity was indicated by phenotypic and functional analysis of positively selected thoracic duct lymphocytes 4 days after transplant and by histopathological examination of skin and gastrointestinal tissue samples 4 weeks later. Therefore, the administration of a CD4-CDR3 peptide is an efficacious approach against the development of GVHD during allogeneic BMT.

Acute Disease↗

PubMed1996

Identification of a human CD4-CDR3-like surface involved in CD4+ T cell function.

The CD4 molecule is expressed on the surface of helper T cells. This molecule contains four tandem external immunoglobulin-like domains (D1-D4), a transmembrane domain, and a cytoplasmic tail. Through the use of molecular modeling techniques, peptide analogs of the CDR3-like region of the human CD4 molecule, analog hPGP, a cyclized peptide 13 amino acids long, was synthesized and tested for its ability to inhibit proliferation in human mixed lymphocyte reactions. A conservative amino acid substitution was made at position 5 (D --> N) to increase its activity and designated hPGP(N). A series of alanine substitution peptides were synthesized based on the sequence of hPGP(N) to determine the importance of each residue to the peptide's function. The substitutions of amino acids in positions 3, 7, and 8 had essentially no effect on the inhibitory activity of hPGP(N), while substitutions of amino acids in positions 4 and 6 increased its inhibitory effect. Alanine substitutions of amino acids in positions 2, 5, and 9 dramatically decreased the inhibitory effect of analog hPGP(N). Molecular modeling of the native CD4-CDR3-like domain suggested that the residues corresponding to positions 2, 5, and 9 of the peptide formed a contiguous surface representing the active site.

Alanine↗

PubMed1996

Synthetic peptides derived from the fourth domain of CD4 antagonize off function and inhibit T cell activation.

We have developed synthetic peptide analogs to analyze novel surface structures of the human CD4 protein potentially involved in T cell activation. Linear and cyclic peptides derived from the FG and CC' loops of the membrane proximal fourth domain of CD4 displayed inhibitory activities in a CD4-dependent immunological assay. These results suggest that the fourth domain of CD4 plays an important role in T cell activation. In addition, we report the synthesis of a highly stable CD4 peptide analog cyclized by the formation of an amide bond between amino and carboxyl termini. Serum stability studies showed that this main-chain cyclic CD4 peptide was highly resistant to proteolytic degradation while the linear and disulfide cyclic peptides were much less stable. The strategy of main chain cyclization of CD4 peptides may represent a promising approach to generate proteolytically stable, orally active immunoregulatory agents.

Amino Acid Sequence↗

PubMed1996

Structure based design and characterization of peptides that inhibit IgE binding to its high-affinity receptor.

We have designed synthetic peptide inhibitors of the interaction between IgE and its high affinity receptor, Fc epsilon RI. The structure of the second domain of CD2 was used as a modelling template for the second alpha-chain domain of Fc epsilon RI, the C-C' loop of which has been implicated in the interaction with IgE. An L-amino acid peptide and a retro-enantiomeric D-amino acid peptide were designed to mimic the conformation of the C-C' region. Both peptides were cyclized by disulphide bond formation between terminal cysteine residues, and show mirror image symmetry by circular dichroism analysis. The C-C' peptide mimics act as competitive inhibitors of IgE binding. The cyclic L- and retro D-peptides exhibited KDs of approximately 3 microM and 11 microM, respectively, for IgE. Further, the peptides inhibit IgE-mediated mast cell degranulation, an in vitro model of an allergic response.

Amino Acid Sequence↗

PubMed1996

Apoptosis is the predominant form of epithelial target cell injury in acute experimental graft-versus-host disease.

Cutaneous and mucosal epithelial cells are primary targets of injury in acute graft-versus-host disease (GVHD), the principal complication of allogeneic bone marrow transplantation. Recent experimental data in skin suggest that early lesion may precede morphologic evidence of direct infiltration by effector cells. The purpose of this study was to further elucidate the mechanism and kinetics of epithelial injury in acute GVHD produced in mouse strains (B10.BR/CBA) receiving bone marrow transplants across minor histocompatibility loci. Skin and tongue mucosa of hosts receiving CD8 T-cell-enriched, whole T-cell-enriched, or T-cell-depleted bone marrow transplants were sequentially harvested and studied histologically and by the terminal uridine deoxynucleotidyl transferase end ligation technique to detect apoptotic cells. Apoptosis involving putative stem cells is the predominant form of cellular injury in acute experimental GVHD. Although apoptosis correlated with the onset of lymphocyte infiltration relatively late in CD8-mediated disease, apoptosis was bimodal in whole T-cell-mediated disease, with an early peak that preceded histologic evidence of lymphocyte infiltration. These findings establish a central role for apoptosis in epithelial cell injury in acute GVHD and indicate that T-cell composition of the donor marrow inoculum may influence the pattern and kinetics of epithelial damage.

Acute Disease↗

PubMed1995

Multiple loci govern the bone marrow-derived immunoregulatory mechanism controlling dominant resistance to autoimmune orchitis.

The existence of immunoregulatory genes conferring dominant resistance to autoimmunity is well documented. In an effort to better understand the nature and mechanisms of action of these genes, we utilized the murine model of autoimmune orchitis as a prototype. When the orchitis-resistant strain DBA/2J is crossed with the orchitis-susceptible strain BALB/cByJ, the F1 hybrid is completely resistant to the disease. By using reciprocal radiation bone marrow chimeras, the functional component mediating this resistance was mapped to the bone marrow-derived compartment. Resistance is not a function of either low-dose irradiation- or cyclophosphamide (20 mg/kg)-sensitive immunoregulatory cells, but can be adoptively transferred by primed splenocytes. Genome exclusion mapping identified three loci controlling the resistant phenotype. Orch3 maps to chromosome 11, whereas Orch4 and Orch5 map to the telomeric and centromeric regions of chromosome 1, respectively. All three genes are linked to a number of immunologically relevant candidate loci. Most significant, however, is the linkage of Orch3 to Idd4 and Orch5 to Idd5, two susceptibility genes which play a role in autoimmune insulin-dependent type 1 diabetes mellitus in the nonobese diabetic mouse.

Animals↗