Spontaneous interstitial nephritis in kdkd mice. II. Characterization of a tubular antigen-specific, H-2K-restricted Lyt-2+ effector T cell that mediates destructive tubulointerstitial injury

In this report, we have examined the effector T cell repertoire in the spontaneous interstitial nephritis of kdkd mice. Lymph node cells from nephritic kdkd mice are capable of transferring this disease into thymectomized, irradiated, and bone marrow-reconstituted CBA/Ca recipients. CBA/Ca mice do not spontaneously develop interstitial nephritis and are normally resistant to the adoptive transfer of nephritic cells, a resistance that in the short term can be attenuated with low-dose cyclophosphamide. We therefore used delayed-type hypersensitivity responses and direct transfer of immune cells under the renal capsule to characterize nephritogenic effector cells from kdkd donor mice. Lyt-2+, L3T4- T cells from the peripheral lymphoid organs of nephritic kdkd mice, after adoptive transfer into cyclophosphamide-pretreated CBA/Ca recipients, mediate an antigen-specific delayed-type hypersensitivity response to renal tubular basement membrane antigens. These cells are restricted by gene products in H-2Kk; they are also present in nephritic, but not in control kidneys. We have also observed this same phenotypic subpopulation of kdkd lymphocytes mediate a destructive interstitial renal lesion within 7 days of being placed under the kidney capsule of CBA/Ca mice. These findings suggest that T lymphocytes reactive to a parenchymal tubular antigen are of substantial importance in the development of spontaneous interstitial nephritis in kdkd mice.     

Spontaneous interstitial nephritis in kdkd mice. I. An experimental model of autoimmune renal disease

Mice of the kdkd strain predictably develop a spontaneous tubulointerstitial nephritis after 8 wk of life. In this report we have examined several aspects of the nephritogenic immune response that seemed potentially relevant to the expression of this progressively destructive renal lesion. Of particular interest is that by direct immunofluorescence we were unable to demonstrate the presence of antibodies to determinants in the tubulointerstitium. Serum and kidney eluates from nephritic mice, furthermore, did not stain any renal structures in normal kidney. We did observe, however, that disease could be transferred through kdkd----CBA/Ca bone marrow chimeras, and prevented, in the reverse direction, by CBA/Ca----kdkd chimeras. The development of the interstitial lesion was markedly inhibited by thymectomy with T cell depletion, but disease could not be adoptively transferred with cells or serum from nephritic mice. The interstitial lesions also did not appear in (kdkd X CBA/Ca)F1 hybrids, and the development of disease in kdkd mice could be inhibited by treatment with adoptively transferred T cells from CBA/Ca mice. With these new findings we now hypothesize that susceptibility to the expression of interstitial nephritis in kdkd mice involves the cellular limb of the immune system, and may be related, in part, to alterations in regulatory T cell function.     

Histone acetyltransferase PCAF regulates inflammatory molecules in the development of renal injury

Kidney diseases, including chronic kidney disease (CKD) and acute kidney injury (AKI), are associated with inflammation. The mechanism that regulates inflammation in these renal injuries remains unclear. Here, we demonstrated that p300/CBP-associated factor (PCAF), a histone acetyltransferase, was overexpressed in the kidneys of db/db mice and lipopolysaccharide (LPS)-injected mice. Moreover, elevated histone acetylation, such as H3K18ac, and up-regulation of some inflammatory genes, such as ICAM-1, VCAM-1, and MCP-1, were found upon these renal injuries. Furthermore, increased H3K18ac was recruited to the promoters of ICAM-1, VCAM-1, and MCP-1 in the kidneys of LPS-injected mice. In vitro studies demonstrated that PCAF knockdown in human renal proximal tubule epithelial cells (HK-2) led to downregulation of inflammatory molecules, including VCAM-1, ICAM-1, p50 subunit of NF-κB (p50), and MCP-1 mRNA and protein levels, together with significantly decreased H3K18ac level. Consistent with these, overexpression of PCAF enhanced the expression of inflammatory molecules. Furthermore, PCAF deficiency reduced palmitate-induced recruitment of H3K18ac on the promoters of ICAM-1 and MCP-1, as well as inhibited palmitate-induced upregulation of these inflammatory molecules. In summary, the present work demonstrates that PCAF plays an essential role in the regulation of inflammatory molecules through H3K18ac, which provides a potential therapeutic target for inflammation-related renal diseases.     

Progressive renal dysfunction and macrophage infiltration in interstitial fibrosis in an adenine-induced tubulointerstitial nephritis mouse model

Adenine phosphoribosyltransferase deficiency in mice or an excessive oral intake of adenine leads to the accumulation of 2,8-dihydroxyadenine (DHA) in renal tubules and that causes progressive renal dysfunction accompanied by interstitial fibrosis. However, the precise mechanism responsible for DHA-induced progressive fibrosis is not fully understood. The present study investigates the possible involvement of monocytes/macrophages in the progressive fibrosis induced by feeding adenine to mice. Urinary calculi were deposited in tubules on day 7 after the initiation of adenine feeding. Elevation of the serum creatinine level and loss of body weight were observed in a time-dependent manner, suggesting the development of typical renal dysfunction induced by the adenine feeding. In renal tissue, mRNA expression of MCP-1, MIP-1α, RANTES, IL-1β, CCR2, TGF-β, α-smooth muscle actin (α-SMA) and collagen 1a1 was increased in parallel. Along with the increased expression of these genes, a remarkable infiltration of macrophages into the tubulointerstitial area was observed in a time-dependent manner. In addition, in the tubulointerstitial area, α-SMA positive fibroblasts were increased in parallel with collagen deposition. These results suggest that the excessive consumption of adenine leads to progressive renal dysfunction in mice. We speculate that the accumulation of DHA in tubules might stimulate epithelium to produce MCP-1 and that profibrogenic TGF-β produced by infiltrated macrophages might stimulate interstitial fibroblasts to produce collagen. These results indicate that macrophage infiltration is one of the triggers that initiates interstitial fibroblast activation and collagen deposition followed by renal dysfunction.     

Functional characterization of a chicken major histocompatibility complex class II B gene promoter

 A 0.7 kilobase (kb) DNA fragment from the 5′ flanking region of a chicken major histocompatibility complex (MHC) class II B gene was cloned into chloramphenicol acetyltransferase (CAT) reporter vectors and was transfected into a chicken macrophage cell line that expresses a low level of MHC class II antigens. Positive orientation-dependent promoter activity of the chicken DNA was evident in a reporter construct containing an SV40 enhancer. Deletion analysis of this 0.7 kb DNA fragment revealed a short fragment in the 3′ end that was crucial for the promoter function and negative regulatory elements (NRE) located further upstream. The conserved MHC class II X and Y boxes did not have a significant effect on promoter activity. Sequence analysis of the 0.7 kb class II B gene upstream region suggests possible involvement of interferon (IFN), E twenty-six specific (ETS)-related proteins, and other factors in regulating this promoter. A chicken T-cell line culture supernatant increased surface expression of MHC class II antigens, as well as class II promoter activity, in this macrophage cell line. This first functional characterization of a chicken MHC class II B gene promoter will aid in understanding the regulatory mechanisms that control the expression of these genes. Received: 9 July 1996 / Revised: 7 October 1996     

Histone acetyltransferase PCAF regulates inflammatory molecules in the development of renal injury

Kidney diseases, including chronic kidney disease (CKD) and acute kidney injury (AKI), are associated with inflammation. The mechanism that regulates inflammation in these renal injuries remains unclear. Here, we demonstrated that p300/CBP-associated factor (PCAF), a histone acetyltransferase, was overexpressed in the kidneys of db/db mice and lipopolysaccharide (LPS)-injected mice. Moreover, elevated histone acetylation, such as H3K18ac, and up-regulation of some inflammatory genes, such as ICAM-1, VCAM-1, and MCP-1, were found upon these renal injuries. Furthermore, increased H3K18ac was recruited to the promoters of ICAM-1, VCAM-1, and MCP-1 in the kidneys of LPS-injected mice. In vitro studies demonstrated that PCAF knockdown in human renal proximal tubule epithelial cells (HK-2) led to downregulation of inflammatory molecules, including VCAM-1, ICAM-1, p50 subunit of NF-κB (p50), and MCP-1 mRNA and protein levels, together with significantly decreased H3K18ac level. Consistent with these, overexpression of PCAF enhanced the expression of inflammatory molecules. Furthermore, PCAF deficiency reduced palmitate-induced recruitment of H3K18ac on the promoters of ICAM-1 and MCP-1, as well as inhibited palmitate-induced upregulation of these inflammatory molecules. In summary, the present work demonstrates that PCAF plays an essential role in the regulation of inflammatory molecules through H3K18ac, which provides a potential therapeutic target for inflammation-related renal diseases.     

Targeting JNK by a New Curcumin Analog to Inhibit NF-kB-Mediated Expression of Cell Adhesion Molecules Attenuates Renal Macrophage Infiltration and Injury in Diabetic Mice

Macrophage infiltration contributes to the pathogenesis of diabetic renal injury. However, the regulatory mechanisms between macrophage infiltration and epithelial cell activation are still unclear. Our previous study found that C66, a novel curcumin analog, was able to inhibit inflammatory cytokine expression in vitro and in vivo. This study further elucidated whether C66 can prevent glucose-induced renal epithelial activation and inflammatory macrophage infiltration by a MAPK/NF-κB medicated mechanism. Our data show that pretreatment with C66 not only significantly reduced high glucose (HG)-induced over-expressions of VCAM-1, ICAM-1 and MCP-1, but also remarkably inhibited NF-κB activation, MAPKs phosphorylation, and subsequently macrophage adhesion in renal epithelial NRK-52E cells. Furthermore, we find that MAPKs, especially JNK, play important roles in HG-induced NF-κB activation, which regulates the over-expression of adhesion molecules in HG-stimulated NRK-52E cells. A molecular docking predicted that C66 may target JNK2, which leads to its anti-inflammatory actions. In vivo, administration of C66 or JNK special inhibitor SP600125 at 5 mg/kg markedly decreased diabetes-induced renal adhesion molecule expression, NF-κB activation, inflammatory cell infiltration, and pathological indexes in the kidneys of diabetic mice. These findings provide a perspective on the renoprotective effects of C66 in diabetes, and outline a novel therapeutic strategy of JNK inhibition for the treatment of diabetic nephropathy.     

Genetically modified bone marrow-derived vehicle cells site specifically deliver an anti-inflammatory cytokine to inflamed interstitium of obstructive nephropathy

In this study, we used genetically modified bone marrow-derived CD11b(+)CD18(+) vehicle cells to deliver IL-1 receptor antagonist (IL-1ra) for treatment of inflamed renal interstitium in an animal model of unilateral ureteral obstruction (UUO). Vehicle cells that expressed the ICAM-1 ligands, CD11b and CD18, were obtained from bone marrow cells of DBA/2j mice and adenovirally transduced with the IL-1ra gene or glucocerebrosidase (GC) gene ex vivo. In kidneys treated to develop UUO, levels of ICAM-1, IL-1 beta, and IL-1R expression increased within 3 days compared with contralateral untreated kidneys in the same mice. Similarly, the macrophage infiltration in the cortical interstitium increased after 3 days in UUO kidneys, but not untreated kidneys. After UUO developed, DBA/2j mice were injected i.v. with either IL-1ra(+) vehicle cells (IL-1ra-treated mice) or GC(+) vehicle cells (GC-treated mice) at 24 h after UUO. Six days after the injection of these vehicle cells, marked increase of CD11b(+) IL-1ra(+) vehicle cells was observed in the ICAM-1-positive interstitium of UUO kidneys from IL-1ra-treated mice. In contrast, no CD11b(+) IL-1ra(+) cells appeared in ICAM-1-negative contralateral kidneys from these mice. Furthermore, the infiltration of macrophages (p < 0.001), expression of ICAM-1 (p < 0.005), and presence of alpha-smooth muscle actin (p = 0.005) in the interstitium of UUO kidneys were significantly decreased in IL-1ra-treated mice compared with GC-treated mice. These findings suggest that IL-1 may contribute to the development of renal interstitial injury and that our method can deliver a functioning gene encoding an antiinflammatory cytokine gene specifically at that site by interacting with local adhesion molecules.     

Human retinoblastoma: in vitro differentiation and immunoglobulin superfamily antigen modulation by retinoic acid

 Suspension and attachment cultures of Y79 human retinoblastoma cells were treated with all-trans retinoic acid (RA) for up to 10 days to assess its effect on growth and cell-surface expression of immunoglobulin superfamily antigens MHC class I and class II, ICAM-1, NCAM and Thy1. RA up to 10 μM induced growth inhibition, and marked morphological differentiation with extension of prominent processes resembling neurites was seen in attachment cultures. However, above 10 μM RA produced extensive cell death. We also observed increased cell-surface expression of MHC class I, ICAM-1, NCAM and Thy1 on Y79 cells treated with 10 μM over 10 days; constitutive MHC class II expression was not apparent, nor did RA treatment appear to induce Y79 cells to express MHC class immunoreactivity. The up-modulation of cell-adhesion molecules (NCAM, ICAM-1 and Thy1) and immune recognition molecules (NCAM, ICAM-1 and MHC class I), associated with reduced growth and tumour cell differentiation, suggests that RA may have a potential role in regulating the growth and development of retinoblastoma tumours. Received: 29 August 1996 / Accepted: 16 January 1997     

Inhibition of Orai1-mediated Ca2+ entry limits endothelial cell inflammation by suppressing calcineurin-NFATc4 signaling pathway

Orai1-dependent Ca²⁺ entry plays an essential role in inflammatory response through regulating T cell and macrophage activation and neutrophil infiltration. However, whether Orai1 Ca²⁺ entry contributes to endothelial activation, one of the early steps of vascular inflammation, remains elusive. In the present study, we observed that knockdown of Orai1 reduced, whereas overexpression of Orai1 potentiated, TNFα-induced expression of adhesion molecules such as ICAM-1 and VCAM-1 in HUVECs, and subsequently blocked adhesion of monocyte to HUVECs. In vivo, Orai1 downregulation attenuated TNFα-induced ICAM-1 and VCAM-1 expression in mouse aorta and the levels of pro-inflammatory cytokines in the serum. In addition, Orai1 knockdown also dramatically decreased the expression of pro-inflammatory cytokines and neutrophil infiltration in the lung after TNFα treatment, and thus protected lung tissue injury. Notably, among all isoforms of nuclear factor of activated T cells (NFATs), TNFα only triggered NFATc4 nuclear accumulation in HUVECs. Knockdown of Orai1 or inhibition of calcineurin prevented TNFα-induced NFATc4 nuclear translocation and reduced ICAM-1 and VCAM-1 expression in HUVECs. Overexpression of NFATc4 further enhanced ICAM-1 and VCAM-1 expression induced by TNFα. Our study demonstrates that Orai1-Ca²⁺-calcineurin-NFATc4 signaling is an essential inflammatory pathway required for TNFα-induced endothelial cell activation and vascular inflammation. Therefore, Orai1 may be a potential therapeutic target for treatment of inflammatory diseases.     

Cytokines in the differentiation of Th1/Th2 CD4+ subsets in leishmaniasis

Leishmania major infect only macrophages in the host, where they reside in endolysosomal compartments into which MHC class II molecules co-localize. Experimental infection in mice has provided a useful model for the differentiation of Th1 CD4+ effector lymphocytes that are required for the generation of IFN-γ that activates the macrophage to a microbicidal state. Genetically susceptible BALB/c mice aberrantly activate Th2 CD4+ effector cells that are ineffective in arresting infection. Increasing evidence suggests that, rather than discrete parasite antigens or MHC molecules, cytokines mediate the critical decision in the developmental switch to either the Th1 or Th2 effector phenotype.     

Angiotensin II induced inflammation in the kidney and in the heart of double transgenic rats

Background  

We are investigating a double transgenic rat (dTGR) model, in which rats transgenic for the human angiotensinogen and renin genes are crossed. These rats develop moderately severe hypertension but die of end-organ cardiac and renal damage by week 7. The heart shows necrosis and fibrosis, whereas the kidneys resemble the hemolytic-uremic syndrome vasculopathy. Surface adhesion molecules (ICAM-1 and VCAM-1) are expressed early on the endothelium, while the corresponding ligands are found on circulating leukocytes. Leukocyte infiltration in the vascular wall accompanies PAI-1, MCP-1, iNOS and Tissue Factor expression. Furthermore we show evidence that Ang II causes the upregulation of NF-kB in our model.     

SAP130 released by damaged tubule drives necroinflammation via miRNA-219c/Mincle signaling in acute kidney injury

Tubules injury and immune cell activation are the common pathogenic mechanisms in acute kidney injury (AKI). However, the exact modes of immune cell activation following tubule damage are not fully understood. Here we uncovered that the release of cytoplasmic spliceosome associated protein 130 (SAP130) from the damaged tubular cells mediated necroinflammation by triggering macrophage activation via miRNA-219c(miR-219c)/Mincle-dependent mechanism in unilateral ureteral obstruction (UUO) and cisplatin-induced AKI mouse models, and in patients with acute tubule necrosis (ATN). In the AKI kidneys, we found that Mincle expression was tightly correlated to the necrotic tubular epithelial cells (TECs) with higher expression of SAP130, a damaged associated molecule pattern (DAMP), suggesting that SAP130 released from damaged tubular cells may trigger macrophage activation and necroinflammation. This was confirmed in vivo in which administration of SAP130-rich supernatant from dead TECs or recombinant SAP130 promoted Mincle expression and macrophage accumulation which became worsen with profound tubulointerstitial inflammation in LPS-primed Mincle WT mice but not in Mincle deficient mice. Further studies identified that Mincle was negatively regulated via miR-219c-3p in macrophages as miR-219c-3p bound Mincle 3′-UTR to inhibit Mincle translation. Besides, lentivirus-mediated renal miR-219c-3p overexpression blunted Mincle and proinflammatory cytokine expression as well as macrophage infiltration in the inflamed kidney of UUO mice. In conclusion, SAP130 is released by damaged tubules which elicit Mincle activation on macrophages and renal necroinflammation via the miR-219c-3p-dependent mechanism. Results from this study suggest that targeting miR-219c-3p/Mincle signaling may represent a novel therapy for AKI.Subject terms: Cell death and immune response, Acute kidney injury     

Regulation by the H-2 gene complex of delayed type hypersensitivity

Identity at the major histocompatibility complex (MHC) was essential for successful transfer of delayed type hypersensitivity (DTH) in mice. The regions of the MHC involved differed according to the antigen used for sensitization. In the case of fowl gamma globulin (FGG), identity atI-A was necessary, whereas with dinitrofluorobenzene (DNFB), identity at theK, I, orD region was sufficient. These different genetic constraints probably reflect differences in the mechanisms by which antigens are presented to T lymphocytes. Cells from sensitized (CBA×C57BL)F₁ mice transferred DTH to FGG into parental-strain mice, but transfer was more effective in C57BL than in CBA with the same cell dose. This phenomenon is governed by the MHC, since there was better transfer intoH-2 ^b than intoH-2 ^k mice, regardless of their backgrounds. It may reflect the activity of an Ir gene-dependent process. Cells of one genotype (e.g., CBA), sensitized in chimeric mice derived from two MHC-incompatible strains (CBAC57BL), transferred DTH to both strains. These results do not support the notion that the genetic constraint observed in DTH transfer may be a result of the necessity for sensitized T and stimulator cells to match an identical MHC-coded cell interaction molecule. Rather, they favor the hypothesis that T cells recognize antigen, not as a naked determinant, but in close association with products of genes of the MHC.     

5-Lypoxygenase Products Are Involved in Renal Tubulointerstitial Injury Induced by Albumin Overload in Proximal Tubules in Mice

The role of albumin overload in proximal tubules (PT) in the development of tubulointerstitial injury and, consequently, in the progression of renal disease has become more relevant in recent years. Despite the importance of leukotrienes (LTs) in renal disease, little is known about their role in tubulointerstitial injury. The aim of the present work was to investigate the possible role of LTs on tubulointerstitial injury induced by albumin overload. An animal model of tubulointerstitial injury challenged by bovine serum albumin was developed in SV129 mice (wild-type) and 5-lipoxygenase-deficient mice (5-LO^–/–). The changes in glomerular morphology and nestin expression observed in wild-type mice subjected to kidney insult were also observed in 5-LO^–/– mice. The levels of urinary protein observed in the 5-LO^–/– mice subjected or not to kidney insult were lower than those observed in respective wild-type mice. Furthermore, the increase in lactate dehydrogenase activity, a marker of tubule damage, observed in wild-type mice subjected to kidney insult did not occur in 5-LO^–/– mice. LTB₄ and LTD₄, 5-LO products, decreased the uptake of albumin in LLC-PK1 cells, a well-characterized porcine PT cell line. This effect correlated with activation of protein kinase C and inhibition of protein kinase B. The level of proinflammatory cytokines, tumor necrosis factor-α and interleukin (IL)-6, increased in mice subjected to kidney insult but this effect was not modified in 5-LO^–/– mice. However, 5-LO^–/– mice subjected to kidney insult presented lower macrophage infiltration and higher levels of IL-10 than wild-type mice. Our results reveal that LTs have an important role in tubulointerstitial disease induced by albumin overload.     

Processing and presentation of self and foreign antigens by the renal proximal tubule.

The renal proximal tubule (PT) in many ways resembles an APC. The PT is one of the few epithelial cells in the body reported to constitutively express the class II MHC molecules required to present Ag to CD4+ T cells. We questioned whether the PT could function as an APC in vitro and in vivo. Fluorescence cytometry demonstrated that the normal CBA/J PT constitutively expressed low levels of class II MHC and that this expression was markedly augmented by either IFN-gamma or systemic Listeria monocytogenes infection. Functionally, the PT from normal CBA/J mice also stimulated T cell hybridomas when cultured in vitro with Ag, and this ability was markedly up-regulated by both IFN-gamma as well as L. monocytogenes infection. To prove that the PT constitutively processed and presented self Ag in vivo, freshly isolated PT from mice transgenic for human alpha 1-antitrypsin were cultured with the appropriate T cell hybridoma in the absence of exogenous Ag. Strong stimulation of the T cell hybridoma occurred. Our data show that the renal proximal tubule processes and presents foreign Ag both in vitro and in vivo, and that it constitutively processes and presents the self Ag hAAT in vivo. These results have important implications for the understanding of renal interstitial autoimmune diseases as well as the interstitial nephritis that occurs in response to foreign Ag.     

Intercellular adhesion molecule-1 expression is required on multiple cell types for the development of experimental autoimmune encephalomyelitis

Many members of the Ig superfamily of adhesion molecules, such as ICAM-1 and VCAM-1, have been implicated in the pathogenesis of multiple sclerosis. Although it is well-established that VCAM-1/VLA-4 interactions can play important roles in mediating CNS inflammatory events in multiple sclerosis patients and during the development of experimental allergic encephalomyelitis (EAE), the contributions of ICAM-1 are poorly understood. This is due in large part to conflicting results from Ab inhibition studies and the observation of exacerbated EAE in ICAM-1 mutant mice that express a restricted set of ICAM-1 isoforms. To determine ICAM-1-mediated mechanisms in EAE, we analyzed ICAM-1 null mutant mice (ICAM-1(null)), which express no ICAM-1 isoforms. ICAM-1(null) mice had significantly attenuated EAE characterized by markedly reduced spinal cord T cell infiltration and IFN-gamma production by these cells. Adoptive transfer of Ag-restimulated T cells from wild-type to ICAM-1(null) mice or transfer of ICAM-1(null) Ag-restimulated T cells to control mice failed to induce EAE. ICAM-1(null) T cells also showed reduced proliferative capacity and substantially reduced levels of IFN-gamma, TNF-alpha, IL-4, IL-10, and IL-12 compared with that of control T cells following myelin oligodendrocyte glycoprotein 35-55 restimulation in vitro. Our results indicate that ICAM-1 expression is critical on T cells and other cell types for the development of demyelinating disease and suggest that expression of VCAM-1 and other adhesion molecules cannot fully compensate for the loss of ICAM-1 during EAE development.     

Positive and negative selection of Tcrb-V6+ T cells

Tcrb-V6⁺ T cells are deleted by an endogenous superantigen probably encoded by a mouse mammary tumor provirus (Mtv), Mtv-7, in association with major histocompatibility complex (MHC) class II molecules. In contrast, Tcrb-V6⁺CD4⁺ T cells are positively selected by MHC class II E molecules in Mtv-7 ^– mice. We have examined the levels of Tcrb-V6⁺CD4⁺ and Tcrb-V6⁺CD8⁺ T cells from six combinations of backcross mice. In this paper we show that: 1) Tcrb-V6⁺CD8⁺ T cells can be positively selected by MHC class I molecules; 2) MHC class II A molecules can also influence the levels of Tcrb-V6⁺CD4⁺ T cells; 3) Mtv-7 ^– NZW mice have a new Mtv, Mtv-44, which co-segregates with a gene encoding the partial deletion ligand for Tcrb-V6⁺ T cells; 4) the remaining Tcrb-V6⁺ T cells from mice with partial deletion of these T cells appear not to be anergized in the periphery. Address correspondence and offprint requests to: K. Tomonari.     

Isolation and mapping of the rabbit DM genes

 Proper peptide presentation by major histocompatibility complex (MHC)-encoded class II antigens is dependent on the products of the MHC DM loci. We identified the rabbit orthologues (RLA-DMA and -DMB) of human HLA-DMA and -DMB and found that they have 76.9% and 78.8% identity with HLA-DMA and -DMB, respectively. Like classical class II MHC genes, RLA-DM genes are more closely related to human HLA-DM genes than to mouse H2-DM. Among the DM family, there is a high degree of variability at the amino terminus of the DMa chains, and length variability in the cytoplasmic tails of both DMα and DMβ. The rabbit DM genes are coexpressed with class II genes in lymphoid tissues, as are the DM genes of other mammals. The RLA-DM locus maps to the class II region of the rabbit MHC, and is flanked by the DP and DOB loci. Despite having some similarities to class II genes of bony fishes, the DM family represents a separate branch of the MHC class II family. Received: 30 May 1998 / Revised: 28 July 1998