The effect of bone marrow and thymus chimerism between non-obese diabetic (NOD) and NOD-E transgenic mice, on the expression and prevention of diabetes

The non-obese diabetic (NOD) mouse is an established animal model of the autoimmune disease, insulin-dependent diabetes mellitus (IDDM). The NOD-E mouse is a transgenic mouse which expresses the I-E molecule (absent in NOD mice). Expression of I-E protects these mice from both insulitis and IDDM. We have investigated the possible mechanisms of this protection by constructing bone marrow, and combined bone marrow and thymus chimeras between NOD and NOD-E mice. Our data suggest that thymic epithelium may play no direct role in either protection against, or promotion of, IDDM. Protection from diabetes is provided either by NOD-E donor bone marrow or NOD-E recipient non-thymic radioresistant cells. The means by which protection may be achieved in this system are discussed.

T cell deletion follows chronic antigen specific T cell activation in vivo

Exposure of mice transgenic for a TCR (F5) to cognate peptide antigen results in thymic depletion of CD4+CD8+ cells and expansion and activation of peripheral CD8+ TCR(tg)+ T cells. In the thymus apoptotic DNA ladder is evident as early as 3 h after peptide injection. Long exposure of intact or thymectomized F5 TCR transgenic mice to peptide antigen leads to depletion of most of the peripheral CD8+ T cells bearing the F5 receptor, with the remaining cells having lower levels of transgenic TCR compared with non-treated animals. In the thymus of intact F5 TCR transgenic mice such continuous exposure to antigen results in the reappearance of CD4+CD8+ with lower levels of the transgenic receptor.

Regulation of expression of the CYP11A (P450scc) gene in bovine ovarian luteal cells by forskolin and phorbol esters

This study examines the transcriptional regulation of the bovine CYP11A (P450scc) gene by activators of protein kinase A and protein kinase C in bovine ovarian luteal cells. Cells were transfected with reporter gene constructs containing deletion mutations of the 5'-flanking region of the bovine CYP11A gene linked to the minimal beta-globin gene. A construct containing -118/-101 base pairs of CYP11A sequence retains the same degree of stimulation by forskolin and inhibition by co-treatment with phorbol 12-myristate 13-acetate as larger constructs. This sequence contains two putative binding sites for nuclear proteins, an AP1-like sequence and an overlapping GA box element. Gel shift analysis using nuclear extracts of bovine ovarian luteal cells demonstrated that both the wild-type -118/-101-base pair sequence and a consensus GC box bound Sp1 or Sp1-like proteins. Mutation of the GA box element completely suppressed stimulation by forskolin. Absence of binding using the same mutated sequence correlated with the reporter gene transcription results. Mutation of the AP1-like site had little effect on forskolin induction of phorbol 12-myristate 13-acetate inhibition. These results indicate that both stimulation by forskolin and inhibition by phorbol esters are mediated by the same GA box element, which binds Sp1 or an Sp1-like protein.

T cell repertoire selection by mouse mammary tumour viruses

Mouse mammary tumour viruses (Mtv) are B-type retroviruses. These can be exogenous, transmitted via maternal milk, or endogenous, as proviral integrations into the mouse genome, transmitted vertically in a Mendelian fashion. A number of different sites of integration of endogenous Mtvs have been reported in various inbred mouse strains. An open reading frame (ORF), within the long terminal repeat (LTR) of Mtv, encodes a type 2 integral membrane glycoprotein. The ORF products are expressed in association with MHC class II molecules at the cell surface and have an affinity for certain T cell receptor (TCR) V beta chains such that CD4+8+ TCR+ double positive thymocytes expressing these V beta chains undergo programmed cell death in mice carrying the appropriate endogenous or exogenous Mtvs. This constitutes a measurable part of negative repertoire selection of the T cell repertoire. Some positive selection of the T cell repertoire also appears to be TCR V beta-specific, although the involvement of polymorphic ligands other than MHC molecules is not apparent. This minireview summarizes the published work on the TCR V beta specificity and chromosomal localization of the various mouse mammary tumour proviral integrations leading to negative selection, and discusses the nature of TCR V beta-specific positive selection.

Loss of the 'azoospermia factor' (AZF) on Yq in man is not associated with loss of HYA

We have typed 9 EBV cell lines from azoospermic or severely oligospermic patients for the expression of H-Y antigen, in order to test the hypothesis of the coincidence of AZF and HYA genes. Of nine patients with cytogenetically normal Y chromosomes, 7 could be tested for HYA expression and of these 6 were H-Y positive. Of the three patients showing Yq structural abnormalities, two could be tested for H-Y expression and one was negative, the other positive. These results therefore show no correlation between spermatogenic failure and the absence of HYA, thus separating the AZF locus from HYA.

A comparative study of T-cell receptor V beta usage in non-obese diabetic (NOD) and I-E transgenic NOD mice

The non-obese diabetic (NOD) mouse is a model for the study of insulin-dependent diabetes mellitus (IDDM). Recently transgenic NOD mice have been derived (NOD-E) that express the major histocompatibility complex (MHC) class II I-E molecule. NOD-E do not become diabetic and show negligible pancreatic insulitis. The possibility pertained that NOD-E mice are protected from disease by a process of T-cell deletion or anergy. This paper describes our attempts to discover whether this was so, by comparing NOD and NOD-E mouse T-cell receptor V beta usage. Splenocytes and lymph node cells were therefore tested for their ability to proliferate in response to monoclonal anti-V beta antibodies. We were unable to show any consistent differences between NOD and NOD-E responses to the panel of antibodies used. Previously proposed V beta were shown to be unlikely candidates for deletion or anergy. T cells present at low frequency (V beta 5+) in both NOD and NOD-E mice were shown to be as capable of expansion in response to antigenic stimulation as were more frequently expressed V beta. Our data therefore do not support deletion or anergy as mechanisms which could account for the observed disease protection in NOD-E mice.

Thymic depletion and peripheral activation of class I major histocompatibility complex-restricted T cells by soluble peptide in T-cell receptor transgenic mice

Injection of mice transgenic for a class I major histocompatibility complex-restricted T-cell receptor with a soluble peptide antigen from influenza virus nucleoprotein results in clonal depletion of double-positive immature thymocytes in the thymus and activation of mature T cells in the periphery, accompanied by a transient up-regulation of the T-cell receptor and CD3 and CD8 coreceptor molecules.

Positive and negative selection in transgenic mice expressing a T-cell receptor specific for influenza nucleoprotein and endogenous superantigen

A transgenic mouse was generated expressing on most (> 80%) of thymocytes and peripheral T cells a T-cell receptor isolated from a cytotoxic T-cell clone (F5). This clone is CD8+ and recognizes alpha alpha 366-374 of the nucleoprotein (NP 366-374) of influenza virus (A/NT/60/68), in the context of Class I MHC Db (Townsend et al., 1986). The receptor utilizes the V beta 11 and V alpha 4 gene segments for the beta chain and alpha chain, respectively (Palmer et al., 1989). The usage of V beta 11 makes this TcR reactive to Class II IE molecules and an endogenous ligand recently identified as a product of the endogenous mammary tumour viruses (Mtv) 8, 9, and 11 (Dyson et al., 1991). Here we report the development of F5 transgenic T cells and their function in mice of the appropriate MHC (C57BL/10 H-2b, IE-) or in mice expressing Class II MHC IE (e.g., CBA/Ca H-2k and BALB/c H-2d) and the endogenous Mtv ligands. Positive selection of CD8+ T cells expressing the V beta 11 is seen in C57BL/10 transgenic mice (H-2b). Peripheral T cells from these mice are capable of killing target cells in an antigen-dependent manner after a period of in vitro culture with IL-2. In the presence of Class II MHC IE molecules and the endogenous Mtv ligand, most of the single-positive cells carrying the transgenic T-cell receptor are absent in the thymus. Unexpectedly, CD8+ peripheral T-cells in these (H-2k or H-2d) F5 mice are predominantly V beta 11 positive and also have the capacity to kill targets in an antigen-dependent manner. This is true even following backcrossing of the F5 TcR transgene to H-2d scid/scid mice, in which functional rearrangement of endogenous TcR alpha- and beta-chain genes is impaired.

Recombination between the X and Y chromosomes and the Sxr region of the mouse

The Sxr (sex-reversed) region that carries a copy of the mouse Y chromosomal testis-determining gene can be attached to the distal end of either the Y or the X chromosome. During male meiosis, Sxr recombined freely between the X and Y chromosomes, with an estimated recombination frequency not significantly different from 50% in either direction. During female meiosis, Sxr recombined freely between the X chromosome to which it was attached and an X-autosome translocation. A male mouse carrying the original Sxra region on its Y chromosome, and the shorter Sxrb variant on the X, also showed 50% recombination between the sex chromosomes. Evidence of unequal crossing-over between the two Sxr regions was obtained: using five markers deleted from Sxrb, 3 variant Sxr regions were detected in 159 progeny (1.9%). Four other variants (one from the original cross and three from later generations) were presumed to have been derived from illegitimate pairing and crossing-over between Sxrb and the homologous region on the short arm of the Y chromosome. The generation of new variants throws light on the arrangement of gene loci and other markers within the short arm of the mouse Y chromosome.

Effect of radiation dose on the development of mixed haemopoietic chimerism following T cell-depleted allogeneic bone marrow transplantation

The presence of mixed haemopoietic chimerism (MXC) was evaluated by cytogenetic and molecular analysis in 48 patients undergoing T cell-depleted BMT. The dose of total body irradiation (TBI) prescribed to all patients (14.4 Gy) was calculated to compensate for the absence of T cells in the graft. The actual midline dose of TBI received, however, differed significantly depending on the method of TBI administration. Thus, 35 adult patients received an average midline dose of 14.3 Gy, while 13 children received a lower dose of 13 Gy. The incidence of MXC in the adult group, who had received very close to 14.4 Gy to the midline, was 34% (12/35), which is lower than in most reported T cell-depleted series. During follow-up, chimerism remained relatively stable with time but varied between haemopoietic lineages. There was no relationship with relapse. MXC in the 13 children who had received a lower midline TBI dose was significantly higher at 69% (9/13) (p < 0.05) and increased to 90% (9/10) if patients who received additional chemotherapy in their conditioning were excluded (p = 0.001). This suggests that, in terms of marrow ablation, relatively small changes in the dose of TBI may be biologically significant, at least at this dose range. Again, in the lower TBI group MXC was not predictive of relapse.

Expression of major histocompatibility complex class I antigens at low levels in the thymus induces T cell tolerance via a non-deletional mechanism

Transgenic CBA (H-2k haplotype) mice expressing the H-2 Kb major histocompatibility complex (MHC) class I gene under control of transcriptional promoter elements from a milk protein gene display high-level H-2 Kb transcription in lactating mammary glands and low-level transcription in skin and thymus of male and virgin female transgenic mice. However, H-2 Kb antigen could be detected only in lactating mammary gland epithelial cells by immunohistological methods. All transgenic mice are tolerant of H-2 Kb since they fail to reject skin grafts from mice expressing H-2 Kb molecules. Furthermore, anti-H-2 Kb cytotoxic responses could not be generated using responder T cells from transgenic mice but T cells from the same mice proliferated, in the presence of interleukin-2, in response to stimulator cells expressing H-2 Kb. Tolerance to H-2 Kb is induced in the thymus since CBA mice grafted with thymus tissue from transgenic mice fail to reject H-2 Kb disparate skin grafts. However, experiments with double-transgenic mice also expressing a T cell receptor with anti-H-2 Kb specificity reveal that tolerance induction is not brought about by elimination of thymocytes bearing H-2 Kb-reactive receptors. Instead, a non-deletional mechanism which results in down-modulation of both CD8 and T cell receptor expression in peripheral T cells correlates with the induction of tolerance in these mice. These data reveal that extremely low levels of self-antigen expression in the thymus are sufficient to induce tolerance via non-deletional mechanisms.

Mechanisms of transplantation immunity

In summary, this chapter describes the biology and genetics of the major and minor histocompatibility antigens and the nature of in vitro and in vivo immune responses to them and to tissue-specific antigens. It reviews the nature and action of immune response genes. It gives an account of how tolerance to histocompatibility antigens was originally defined and the prospects of intervention aimed at establishing tolerance to these and tissue-specific antigens in adult animals, including man.

A molecular deletion map of the Y chromosome long arm defining X and autosomal homologous regions and the localisation of the HYA locus to the proximal region of the Yq euchromatin

41 Y-linked DNA probes that detect sequences on the Y chromosome long arm have been used to analyse genomic DNA from a series of 23 patients with deletions of Yq. Southern blot analysis has differentiated 15 distinct breakpoints, which divide Yq into 14 mapping intervals. From the pattern of DNA sequences present in each patient, it has been possible to produce a congruent deletion map, with the exception of two cases which are not compatible with the consensus order. These patients can be explained by the presence of inversion polymorphisms on Yq in the general population or by complex rearrangements induced during the formation of the deleted chromosomes. The distribution of sequences on the Y long arm has defined distinct regions of homology with autosomes, the Y short arm and the long and short arms of the X. A number of the patients have been typed for the presence or absence of H-Y antigen (as determined by the cytotoxic T-cell assay) and it has been possible, from analysis of informative cases, to assign the locus to the proximal region of the Yq euchromatin.

Deletion mapping of H-Y antigen to the long arm of the human Y chromosome

A gene encoding or controlling the expression of the H-Y transplantation antigen was previously mapped to the human Y chromosome. We now report the sublocalization of this gene on the long arm of the human Y chromosome. Eight patients with Y-chromosomal abnormalities were examined with a series of existing and new DNA markers for the Y chromosome. The resulting deletion map was correlated with H-Y antigen expression. We conclude that the H-Y antigen gene maps to a portion of deletion interval 6 that is identified by specific DNA markers.

Determination of aromatase cytochrome P450 messenger ribonucleic acid in human breast tissue by competitive polymerase chain reaction amplification

Local production of estrogen in breast tissue may influence the growth of breast cancers. Peripheral conversion of C19 steroids to estrogens is catalyzed by the aromatase enzyme complex which is comprised of a specific form of cytochrome P450, aromatase cytochrome P450 (P450AROM) and the flavoprotein, NADPH-cytochrome P450 reductase. To evaluate P450AROM mRNA levels in breast tissue, a specific competitive polymerase chain reaction amplification procedure was devised. In this method, a rat P450AROM complementary RNA is coamplified as an internal standard in order to compare amplification reactions. The amplification products are recognized by hybridization with 32P-labeled oligonucleotides specific for each species. Densitometry is used to quantitate autoradiographs. Initial studies using RNA from whole breast tissue obtained from reduction mammoplasty revealed linearity of the relationship between the densitometer signal from the human amplification product and total RNA concentration. Breast tissue was then separated into a floating adipocyte fraction and a pelleted fraction containing the other cellular elements by collagenase digestion and centrifugation. Comparison of specific content of aromatase amplification product per unit weight of RNA extracted from adipocytes and pelleted cells revealed considerably higher levels in the RNA from the nonadipocyte fraction. Immunocytochemical characterization of this fraction revealed the presence of several cell types including macrophages, ductal epithelial cells, and endothelial cells, but primary cells of stromal origin.

A new approach to the cloning of genes encoding T-cell epitopes

The molecular structure of antigens recognized exclusively by T cells, such as minor histocompatibility antigens and some antigens that provoke autoimmune responses, has proved difficult to determine. Recently, several antigens induced on tumor cells by mutagen treatment have been cloned by transfection of genomic DNA libraries into P1.HTR cells, screening for antigen expression using T-cell clones, and subsequent recovery of the integrated DNA by cosmid rescue. We have modified this technique and have stably transfected P1.HTR cell lines with polyoma T antigen, which allows episomal replication of the shuttle vector, pCDM8. Using pCDM8-CAT constructs, we have determined the frequency of transfection and plasmid copies taken up per cell under optimal transfection conditions. Using a pCDM8 construct which expresses the tumor-specific antigen, P91A (pCDM8-tum-), that is recognized by a T-cell clone, we have found that cells transfected with this antigen can be recognized by the T-cell clone when they are present at only 1%-3% of a mixed population. Progeny of a single cell transfected with pCDM8-tum-: pCDM8-CAT at proportions of 1:10, 1:25, and 1:50 are recognized by the T-cell clone. Furthermore, Hirt extracted plasmid DNA from transfectants expressing the tum- antigen can be amplified in bacteria, transfected back into P1.HTR recipients, and recognized by the T-cell clone. This approach should enable reasonably rapid screening of cDNA libraries for even relatively low abundance messages encoding, for example, minor histocompatibility and alloantigens, and allow their subsequent cloning.

T-cell-targeted immunotherapy

The pace of T-cell research is matched only by the speed with which fundamental advances are being developed as new therapies. This report from a recent meeting updates developments in a number of immunointervention strategies.

PCR-analyzed microsatellites of the mouse genome--additional polymorphisms among ten inbred mouse strains

Eighty sequences from the mouse genome database containing microsatellites (simple sequence repeats) have been analyzed for size variation among ten different inbred strains of mice; 62/80 (77.5%) showed polymorphism of at least three alleles. We have been able to detect all the polymorphisms by agarose gel electrophoresis, often running the gels for up to 3 h. Between individual pairs of mouse strains to be used in chromosomal mapping studies in our laboratory, 35-60% polymorphism occurred. There are potentially enough microsatellites within the mouse and human genome to have a marker at every 1-cM distance. This simple approach will, therefore, continue to be useful in genome mapping studies, leading eventually to high-resolution maps of both the mouse and human genomes; this should allow for physical mapping and cloning of specific genes.

Phenotypic and functional studies of human peripheral blood lymphocytes engrafted in scid mice

CB.17 mice homozygous for the scid defect have been used as recipients of peripheral blood lymphocytes (PBL) from normal humans and from patients suffering from common variable immunodeficiency (CVI) types A and B. Following intra-peritoneal injection of PBL, such mice become chimeric with human cells, as evidenced by the presence in their serum of human immunoglobulins, which persist for a number of months. Under these conditions, B cells from CVI patients are also triggered to produce immunoglobulin. In contrast, T cells in the inocula, although they persist for 1 or 2 months in the peritoneal cavity, do not appear to function normally in antigen-specific responses and they do not recirculate in the recipient mice.

Minor histocompatibility antigens

Immune responses against foreign tissue or organs can be directed against alloantigenic differences between donor and host encoded by genes of the major histocompatibility complex (MHC; HLA in man and H-2 in mouse). However, when MHC antigens are matched, as in HLA-identical siblings, or between different mouse strains sharing the same H-2 haplotype, graft rejection still occurs and is then directed against alloantigenic differences termed minor histocompatibility (H) antigens. Their molecular nature is not yet determined but they are recognised by T cells in an MHC-restricted manner, so are assumed to be derived from molecules co-expressed with MHC class I or II glycoproteins, possibly as peptides or as "super-antigens". The genes encoding them are scattered throughout the genome, including the Y chromosome, on which the H-Y antigen gene has been mapped in both man and mouse. One striking feature of minor H antigens is their recognition by T cells but not by antibodies. This made work with them, before our ability to generate T cell responses and maintain T cell clones in vitro, very slow but currently the use of MHC-restricted T cell clones has enabled detailed mapping studies and should eventually allow for their molecular characterisation.

Characterization of pancreatic islet cell infiltrates in NOD mice: effect of cell transfer and transgene expression

Insulin-dependent diabetes mellitus can be transferred into young irradiated non-obese diabetic (NOD) mice by spleen cells from a diabetic NOD donor. T cells (both L3T4+ and Ly-2+) enter the pancreas 2 weeks following transfer. They are present initially at peri-islet locations but progressively infiltrate the islet with accompanying beta cell destruction. The infiltrate is heterogeneous with respect to V beta usage. Inflammatory macrophages (Mac-1+, F4/80+) can be detected at peri-islet locations at 1 week after transfer and continue to be recruited during the disease process. Their presence at the initiation of disease suggests that their primary function may be autoantigen presentation. Increased expression of major histocompatibility complex (MHC) class I molecules is observed on both endocrine and exocrine tissue in areas of intra-islet infiltration. MHC class II and ICAM-1 expression was restricted to the cells constituting the inflammatory infiltrate. Expression of these molecules was not observed on beta cells implying that presentation of autoantigen by the beta cell itself does not play a role in the beta cell destruction in NOD mice.

Genes encoding ligands for deletion of V beta 11 T cells cosegregate with mammary tumour virus genomes

The T-cell receptor (TCR) repertoire is selected in the thymus after rearrangement of genes encoding TCR alpha and beta chains. Selection is based on the recognition by newly emergent T cells of self-ligands associated with molecules of the major histocompatibility complex: some combinations result in positive selection, others in negative selection. Negative selection, or clonal deletion, is an important mechanism for eliminating autoreactive T cells. A group of self-ligands involved in clonal deletion was identified because they, like exogenous superantigens, were recognized by almost all T cells expressing particular TCR V beta genes. V beta 17a T cells are deleted by a tissue-specific ligand; V beta 6, V beta 7, V beta 8.1 and V beta 9 T cells are deleted by the minor lymphocyte-stimulating (Mls) determinant Mls-1a; V beta 3 T cells by Mls-2a and Mls-3a; V beta 11 T cells by ligands encoded by independently segregating genes; and V beta 5 T cells by ligands encoded by two genes. Chromosome mapping using recombinant inbred strains of mice and classic backcrosses show that Mls-1a in DBA/2 mice is encoded on chromosome 1, that one of the two ligand genes for deletion of V beta 5 T cells maps to chromosome 12 and that a ligand gene for V beta 11 deletion is linked to the CD8 locus on chromosome 6. Here we present evidence from three sets of backcross mice for concordance between V beta 11 deletion ligand genes on chromosomes 6, 12 and 14 and endogenous mouse mammary tumour virus integrant (Mtv) genomes.(ABSTRACT TRUNCATED AT 250 WORDS)

Cyclosporine monitoring by fluorescence polarization immunoassay

The monitoring of cyclosporine levels in whole blood and serum has become a routine procedure for the post-transplant management of immunosuppression. We have developed fluorescence polarization immunoassays for cyclosporine in whole blood and in serum using a monoclonal antibody. These assays are fast (20 determinations in less than 22 min), sensitive (25 micrograms/L for whole blood samples and 10 micrograms/L for serum samples), and precise (CV less than 7% in both assays). Cross-reactivities with AM1 (Metabolite 17) and AM4N (Metabolite 21) are less than 8.5 and 2.5%, respectively, for both assays.

Regulation of expression of the genes encoding steroidogenic enzymes

In recent years it has become apparent that tropic hormones involved in steroidogenesis act to regulate the expression of the enzymes involved in the various steroidogenic pathways. This is particularly evident in the ovary where the episodic secretion of steroids throughout the ovarian cycle is regulated largely by changes in the levels of the particular enzymes involved in each step of the steroid biosynthetic pathways. Recently, the genes for the various cytochrome P450 species involved in ovarian steroidogenesis, namely cholesterol side-chain cleavage P450 (P450SCC), 17 alpha-hydroxylase P450 (P450(17 alpha], and aromatase cytochrome P450 (P450AROM) have been isolated and characterized, making it possible to study the regulation of expression at the molecular level. To this end, a series of chimeric constructs have been prepared in which fragments of the 5'-untranslated region of bovine P450(17 alpha) and P450SCC have been inserted upstream of the chloramphenicol acetyl transferase (CAT) and beta-globin reporter genes. These constructs have been used to transfect primary cultures of bovine luteal and thecal cells. The results indicate that cAMP responsiveness lies within defined regions of genes which do not contain a classical CRE, similar to previous results utilizing adrenal cells in culture. Furthermore, although constructs containing both the P450(17 alpha) and P450SCC 5'-upstream regions are expressed in both luteal and thecal cell cultures, only those containing the P450SCC sequences are expressed in luteal cells. Studies on the expression of P450AROM indicate that the promoter which is responsible for its expression in human placenta is not operative in the corpus luteum. Thus estrogen biosynthesis may be regulated by the differential use of tissue specific promoters, thus accounting for the complexity and multifactorial nature of the expression of this activity.

Transfer of diabetes in mice prevented by blockade of adhesion-promoting receptor on macrophages

Insulin-dependent diabetes mellitus (IDDM) is a disease with an autoimmune aetiology. The non-obese diabetic mouse is a good spontaneous animal model of the human disease, with IDDM developing in 50-80% of female mice by the age of 6 months. The disease can be transferred by splenic T cells from diabetic donors and is prevented by T-cell depletion. The mechanism(s) by which the beta cell is specifically destroyed is not known, but T cells and macrophages have both been implicated, based on the presence of macrophages in the infiltrated islet and the ability of chronic silica treatment to prevent disease. The monoclonal antibody 5C6 is specific for the myelomonocytic adhesion-promoting type-3 complement receptor (CR3 or CD11b/CD18) and does not bind to T cells. Here we show that blockade of macrophage CR3 in vivo prevents intra-islet infiltration by both macrophages and T cells and inhibits development of IDDM. We conclude that both T cells and macrophages have an essential role in the onset of IDDM.

Canadian therapists' priorities for clinical research: a Delphi study

Clinically relevant physical therapy research questions were developed by a Delphi technique among 55 teaching hospital physical therapists. The Delphi technique used in this study involved three rounds of questionnaires that included characteristics of anonymity, feedback, ranking with statistical scoring, and use of informed respondents. Fifty-eight initial research questions were narrowed to 11 according to their potential benefit for the patient, for the practice of physical therapy, and for decreasing health care costs. A literature review revealed that each of the 11 questions were as yet unanswered. The use of the survey results to guide and plan for clinical research in physical therapy is discussed.

Prevention of insulin-dependent diabetes mellitus in non-obese diabetic mice by transgenes encoding modified I-A beta-chain or normal I-E alpha-chain

Insulin-dependent diabetes mellitus (IDDM) is a disease with an autoimmune aetiology. The inbred non-obese diabetic (NOD) mouse strain provides a good animal model of the human disease and genetic analysis suggests that, as in man, at least one of the several genes controlling the development of IDDM is linked to the major histocompatibility complex. The NOD mouse does not express I-E owing to a deletion in the promoter region of the I-E alpha-chain gene, and the sequence of NOD I-A beta-chain in the first external domain is unique with His 56 and Ser 57 replacing Pro and Asp, respectively, at these positions. There has been considerable interest in the role amino acid 57 might have in conferring susceptibility to autoimmune diseases, including IDDM. The presence of a charged residue (such as Asp) at this position might affect the conformation of the peptide binding groove. But it could be assumed that Pro 56 gives rise to a different conformation of I-A beta-chain than does His 56. We therefore constructed transgenic NOD mice in which the transgene encoded a modified A beta nod with Pro 56, and studied its effect on the development of IDDM in this mouse strain. Previous studies have suggested that NOD mice expressing I-E as a result of the introduction of an I-E alpha-chain (E alpha) transgene are protected from the development of insulitis and hence IDDM. To explore further the protective effect of this molecule we constructed a second class of transgenic NOD mouse carrying an E alpha d transgene. Both transgenes protected the mice from IDDM, but this was not associated with a complete deletion of any T cells expressing commonly used T-cell receptor V beta genes.

The involvement of Ly2+ T cells in beta cell destruction

The non-obese diabetic (NOD) mouse is considered to be a good model of human Type I diabetes mellitus. Both sexes develop insulitis starting at about 6 weeks of age, and onset of diabetes follows at about 30 weeks in females, but later and much less frequently in males. In some mice (but not all) infiltration of the islets leads to selective destruction of insulin-producing beta cells, which is marked by clinically overt diabetes and is thought to be an autoimmune response mediated by T cells. Both L3T4+ and Ly2+ cells have been implicated in the destructive process and we have used an in vivo transfer system, together with histological studies on the pancreas, to demonstrate the essential role played by Ly2+ T cells in the destruction of beta cells in diabetic mice.

Characterization of the anticoagulant activities from a Brazilian arrow poison

A recent report indicated that an arrow poison used by the native Indians of Rondonia, Brazil, to kill small animals was associated with profuse bleeding. The arrow poison was prepared from the bark of a tree, known locally as Tike-Uba. We have obtained bark and sap specimens from this tree and have characterized a potent anticoagulant activity in both the crude bark and sap samples as well as in more highly purified preparations. An aqueous extract of the bark significantly prolongs both prothrombin times and activated partial thromboplastin times in plasma based assays. Further fractionation of the bark extract and sap by molecular weight indicated that all of the anticoagulant activity could be isolated in a molecular weight fraction of equal to or greater than 30,000 daltons. The anticoagulant activity was also further purified by C-18 reverse phase chromatography. When highly purified preparations of the anticoagulant activity from the Tike-Uba tree were examined in specific blood coagulation enzyme assays utilizing chromogenic substrates, the highest inhibitory potency was found versus thrombin, followed by factor Xa. These studies establish the presence of a compound(s) in a Brazilian arrow poison, which potently disrupts mammalian blood clotting, and which may account for some of the observed toxicities associated with the arrows.

A glycophospholipid anchor is required for Qa-2-mediated T cell activation

A number of lymphocyte surface proteins are anchored in the cell membrane by glycophosphatidyl inositol (known as GPI) linkages instead of hydrophobic protein domains. Treatment of mouse T lymphocytes with antibodies specific for two such proteins, Thy-1 and Ly-6, are known to induce proliferation. We have found that antibodies specific for Qa-2, a GPI-anchored class I histocompatibility antigen, can also activate mouse T cells. To determine whether the GPI-anchor is important for this pathway of cell activation, we produced transgenic mice expressing either normal GPI-anchored Qa-2, or Qa-2 molecules with a membrane-spanning protein domain derived from H-2. Our studies show that only lymphocytes from transgenic mice carrying GPI-anchored forms of Qa-2 can be activated in vitro by Qa-2-specific antibodies. We also show that transgenic mouse T cells expressing a GPI-anchored form of H-2Db can be activated by anti-H-2Db antibodies. These results strongly indicate that the GPI-anchor is critical for this pathway of T cell activation.

Antistasin, a leech-derived inhibitor of factor Xa. Kinetic analysis of enzyme inhibition and identification of the reactive site

Antistasin is a 119-amino acid protein isolated from the salivary glands of the Mexican leech Haementeria officinalis. The determination of the primary structure of antistasin revealed that the protein is highly disulfide-bonded with a 2-fold internal homology. Antistasin exhibits a potent anticoagulant activity purportedly due to the selective inhibition of Factor Xa (Tuszinsky, G. P., Gasic, T. B., and Gasic, G. J. (1987) J. Biol. chem. 262, 9718-9723). In the present study a detailed kinetic analysis of the inhibitory interaction between antistasin and Factor Xa was performed. In addition, the specificity of antistasin was examined by testing its ability to inhibit a variety of serine proteinases. Utilizing purified antistasin and a tripetidyl p-nitroanilide substrate, antistasin was shown to act as a reversible inhibitor of Factor Xa which exhibits slow-tight binding kinetics. Antistasin reacts stoichiometrically with Factor Xa with inhibition displaying a mixed, primarily competitive type. The inhibition is partial in the presence of Ca2+ and becomes complete in the absence of Ca2+. The estimated dissociation constant for the enzyme-inhibitor complex is between 0.31 and 0.62 nM. After binding to Factor Xa, antistasin is cleaved at a single site to yield a modified inhibitor. Automated gas-phase sequence analysis of the modified inhibitor indicates the arginine residue at position 34 in antistasin occupies the P1 position of the reactive site. These data indicate that the leech has evolved a highly selective and potent inhibitor of coagulation Factor Xa that shares several mechanistic similarities with other serine proteinase inhibitors.

Quantitative computed tomography reflects vertebral fracture morbidity in osteopenic patients

We studied the relationship between spontaneous vertebral compression fractures and lumbar vertebral trabecular bone density in 69 consecutive patients with suspected osteopenia. Seven had biopsy-confirmed osteomalacia. The remaining 62 were divided into three groups: group 1--asymptomatic patients suspected of having osteopenia on plain films, but with no vertebral compression fractures (N = 24); group II--those with one to five vertebral compression fractures (N = 16); and group III--those with six or more vertebral compression fractures (N = 22). A quantitative computed tomographic (QCT) scan of the lumbar spine was performed on all patients. Patients in group I had QCT values of 94 +/- 23 mg/cm3 (mean +/- SE); those in group II had QCT values of 66 +/- 28 mg/cm3; and those in group III had values of 34 +/- 28 mg/cm3. There were significant differences among all groups (P less than .001), although there was considerable overlap of individuals among the groups. There was no significant difference between the mean QCT value of patients with one compression fracture and the value of those with between two and five compression fractures. Patients with biopsy-proven osteomalacia had higher vertebral trabecular bone density than patients with osteoporosis and compression fractures. Our study provides evidence suggesting a strong inverse relationship between QCT-measured vertebral bone density and the presence of vertebral compression fractures in a group of osteopenic patients.

Isolation and structural characterization of a potent inhibitor of coagulation factor Xa from the leech Haementeria ghilianii

The present work reports the discovery and characterization of an anticoagulant protein in the salivary gland of the giant bloodsucking leech, H. ghilianii, which is a specific and potent inhibitor of coagulation factor Xa. The inhibitor, purified to homogeneity, displayed subnanomolar inhibition of bovine factor Xa and had a molecular weight of approximately 15,000 as deduced by denaturing SDS-PAGE. The amino acid sequence of the first 43 residues of the H. ghilianii derived inhibitor displayed a striking homology to antistasin, the recently described subnanomolar inhibitor of factor Xa isolated from the Mexican leech, H. officinalis. Antisera prepared to antistasin cross-reacted with the H. ghilianii protein in Western Blot analysis. These data indicate that the giant Amazonian leech, H. ghilianii, and the smaller Mexican leech, H. officinalis, have similar proteins which disrupt the normal hemostatic clotting mechanisms in their mammalian host's blood.

Minor transplantation antigens: their role in shaping the T cell repertoire

Minor transplantation, or histocompatibility (H), antigens are the targets of host-versus-graft (hvg) and graft-versus-host (gvh) reactions that occur when organs or tissues are exchanged between members of the same species who, although genetically not identical, are matched for their major histocompatibility complex (MHC) encoded transplantation antigens. Genes encoding minor H antigens map outside the MHC, on a number of different chromosomes. Whilst gvh and hvg reactions against individual minor H antigens are relatively weak, certainly in comparison with such reactions against MHC antigens, the presence of multiple minor H differences (the situation encountered in man) gives rise to very vigorous reactions that can endanger the survival of graft or host, or both. This is the pathological role of minor H antigens and, indeed, it was this role which was first designated to the MHC antigens, before their physiological role as guidance molecules for T lymphocytes was discovered. Recently, a potential physiological role for minor H antigens has been uncovered by the finding that the presence of certain minor H alleles in mice leads to removal in the thymus (negative selection) of all those T cells expressing a particular T cell receptor (TCR) gene. Such cells therefore never reach the periphery, where they might otherwise give rise to autoimmune reactions. The T cell repertoire is thus moulded by at least some minor H antigens, which may therefore be regarded as non-MHC immune response genes. Furthermore, T cell receptor usage by T cells specific for allogeneic minor H antigens appears not to be representative of T cell receptor usage in the peripheral pool.(ABSTRACT TRUNCATED AT 250 WORDS)

Florid radiological appearance of megakaryoblastic leukaemia--an aid to earlier diagnosis

Accurate diagnosis of leukaemia is essential to enable appropriate treatment. The diagnosis is made by cytological and cytochemical techniques but radiology may, however, serve a very useful role in first suggesting a diagnosis. We present here four cases of megakaryoblastic leukaemia (AML FAB classification M7), three of which have strikingly similar unusual radiological changes. A review of the literature suggests this condition has previously been diagnosed as acute or malignant myelofibrosis, and the megakaryoblastic nature of the disease was not recognised. The presence of these radiological features may therefore prompt specific immunocytochemical testing, in a disease that is otherwise difficult to diagnose early.

H-Y responses of non-obese diabetic (NOD) mice

Female non-obese diabetic (NOD) mice were tested for their ability to make responses to the male-specific (H-Y) transplantation antigen. In vivo assessment of this ability was made using skin graft rejection. A proportion (60%) spontaneously rejected NOD male tail skin by 80 days post-transplantation. The detection of the generation of H-Y-specific cytotoxic T cells, following in vivo priming and secondary in vitro restimulation, was carried out using a conventional 51Cr release assay. Female NOD mice primed either by skin grafting, intraperitoneal (i.p.) or footpad (f.p.) injection of male NOD spleen cells could be induced to make anti-H-Y cytotoxic responses, but not every immunized mouse responded. The nature of the H-Y-reactive T cells was investigated further by the in vitro isolation of T-cell clones of which some were H-Y specific.

Location of the genes controlling H-Y antigen expression and testis determination on the mouse Y chromosome

Sex-reversed XX male mice that carry the variant form of the testis-determining Sxr region, Sxr', do not express male-specific H-Y antigen. In a stock of mice segregating for Sxr', we detected an exceptional XX male that proved positive for H-Y antigen. DNA fingerprinting revealed that the banding pattern characteristic of Sxr' had been replaced by the pattern associated with the native testis-determining region of the normal Y chromosome of that stock, presumably by pairing and crossing-over between the two testis-determining regions of the father's Y Sxr' chromosome. Pairing between the two ends of such a chromosome in a loop-like configuration has been observed by electron microscopy. However, an anomalous crossing-over event of this kind would only give rise to the observed result if the native homologue of the Sxr region were situated on the very minute short arm of the Y chromosome. We therefore conclude that the two linked genes Tdy and Hya, controlling testis determination and H-Y antigen expression, respectively, are located on the short arm of the mouse Y chromosome.