Biomedical subjects

M Kronenberg

Publications and source records attributed to M Kronenberg.

At least 37 records · Page 2Linked to original sources

PubMed1994

Structure and function of H-2 T (Tla) region class I MHC molecules.

The T region of the mouse major histocompatibility complex (MHC) encodes a relatively large number of nonclassical or nonpolymorphic class I genes. In BALB/c mice, at least five of these genes are likely to encode a functional class I gene product. Some of these T region products are ubiquitously expressed, while others are expressed by just a few tissues. In the second category, the thymus leukemia (TL) antigen, which is encoded in the T region by T3 and T18 genes, is expressed primarily by intestinal epithelial cells and thymocytes. Inspection of the sequences of the alpha 1 and alpha 2 domains, which could encode a peptide binding site in these molecules, indicates that in several cases conserved amino acids important for peptide binding by classical class I molecules are present, suggesting that these nonclassical class I molecules can bind nonamer peptides. On the other hand, analysis of the sequence of the T10d gene product suggests that it can not bind nonamer peptides in a fashion similar to classical class I molecules. Although there are so far no examples of the recognition of defined peptides in the context of T region gene products, there are several examples of T cell recognition of these class I molecules. Both alpha beta and gamma delta T cell receptors are involved in this recognition. Transgenic mice that over express the TL antigen show a variety of abnormalities in thymocyte differentiation and function, providing some support for the hypothesis that this nonclassical class I molecule plays a role in T-cell differentiation. Despite this, the most likely function for T region encoded and other nonclassical class I gene products is a specialized antigen presenting function, perhaps in restricted anatomic sites or to specialized T-cell populations.

Amino Acid Sequence↗

PubMed1993

The alpha 3 domain of the Qa-2 molecule is defective for CD8 binding and cytotoxic T lymphocyte activation.

Qa-2 is a nonclassical class I molecule encoded by the Q7 gene within the mouse major histocompatibility complex (MHC). Results from previous experiments on Qa-2, and on a chimeric Ld molecule (LQ3) in which the alpha 3 domain is encoded by Q7b, suggested that the alpha 3 domain of Qa-2 does not carry out the functions typical of the alpha 3 domains in other classical and nonclassical class I antigens. Class I molecules that contain the Qa-2 alpha 3 domain are poorly recognized by primary cytotoxic T lymphocytes (CTLs), and do not function normally in either positive or negative selection in vivo. By employing a cell-cell adhesion assay we demonstrate directly that the Qa-2 alpha 3 domain in the context of the LQ3 hybrid molecule cannot bind to human CD8, although other mouse class I alpha 3 domains bind efficiently. In addition, CD8-dependent CTL-mediated lysis of target cells, in a system which requires mouse CD8-class I alpha 3 domain interactions, is deficient in cells that express the Qa-2 alpha 3 domain. When combined with our earlier work on LQ3 transgenic mice, these results provide additional molecular support for the hypothesis that interaction with CD8 is required for both positive and negative selection of class I restricted T cells in the thymus. As the Qa-2 alpha 3 domain sequence does not differ from the previously defined minimal CD8 binding sequence of other class I molecules, these results also suggest that additional amino acids in the alpha 3 domain must be critical for CD8 binding and CTL activation.

Amino Acid Sequence↗

PubMed1993

Regional specialization of the mucosal immune system. Intraepithelial lymphocytes of the large intestine have a different phenotype and function than those of the small intestine.

Intraepithelial lymphocytes (IEL) are found in both the small and the large intestine. We demonstrate that there are a number of striking phenotypic and functional differences between the two populations of IEL isolated from mice. In the large intestine, the majority of IEL express the alpha beta TCR, and among these TCR-alpha beta+ lymphocytes, CD4+ cells are as prevalent as CD8+ cells. In contrast, in the small intestine, most of the TCR-alpha beta+ IEL express CD8, and an increased percentage of cells express TCR-gamma delta. In addition, most TCR-gamma delta+ IEL isolated from the large intestine (LI-IEL) are CD4- CD8- cells, as compared to TCR-gamma delta+ IEL isolated from the small intestine (SI-IEL), which are predominantly CD8+. Furthermore, CD2 and the lymph node homing receptor, L-selectin, are expressed by most LI-IEL but not by SI-IEL. Furthermore, LI-IEL have much less cytolytic activity than SI-IEL. These data suggest that LI-IEL are a distinct population of lymphocytes that may have a different immunologic role than that of SI-IEL.

Animals↗

PubMed1993

Intestinal intraepithelial lymphocytes are activated and cytolytic but do not proliferate as well as other T cells in response to mitogenic signals.

Compared with T lymphocytes from other organs, intestinal intraepithelial lymphocytes (IEL) proliferate weakly in response to CD3/TCR ligation, and they do not respond at all to treatment with other mitogenic stimuli. These signals also failed to induce expression of the IL-2R alpha-chain on the surface of most IEL. IEL from germ-free mice, from V gamma 1.1-transgenic mice, and from beta 2-microglobulin-deficient mice also gave a weak proliferative response. Therefore, the low proliferative response is not linked to the level of exposure to gut bacterial flora, the V gamma region expressed by the TCR-gamma delta + IEL, or the presence of class I molecules that may be recognized by CD8+ IEL. The relatively small amount of proliferation in response to TCR signaling, therefore, is not likely to be the result of induction of anergy caused by previous contact with Ag. In contrast, ligation of the CD3/TCR complex could elicit a rapid cytotoxic response and serine esterase release by IEL. The unusual functional capabilities and the activation state of IEL are independent of the TCR isotype expressed by these cells. Freshly isolated IEL have a high intracellular microtubule-associated protein kinase-2 (MAP-2K) activity level, further suggesting that these cells are activated despite their weak proliferative response. Consistent with this, MAP-2K is tyrosine-phosphorylated in both untreated and PMA-treated IEL. In contrast, MAP-2K activation and tyrosine phosphorylation occur in other T cells only when they are activated by PMA or other treatments. MAP-2K activity also is elevated in IEL from germ-free mice, demonstrating that activation does not depend on normal levels of exposure to bacterial flora. The activation of protein kinases such as MAP-2K could reflect the differentiation state of IEL or Ag receptor stimulation of some of these cells by epithelial cells in the preparation.

Animals↗

PubMed1993

Selection of T lymphocytes bearing limited T-cell receptor beta chains in the response to a human pathogen.

Delayed-type hypersensitivity (DTH) is a classic measure of T-cell responsiveness to foreign antigen. To estimate the extent of the T-cell repertoire in the DTH response to a human pathogen, we measured T-cell receptor (TCR) beta-chain variable-region (V beta) gene usage in reversal reactions in leprosy. Reversal reactions represent naturally occurring DTH responses in leprosy, in which augmentation of T-cell responses to Mycobacterium leprae is concomitant with clearance of bacilli from lesions. T cells using the V beta 6-, V beta 12-, V beta 14-, and V beta 19-encoded TCRs were strikingly overrepresented in the lesions of patients as compared to blood and pre-DTH lesions from the same individuals. Furthermore, these data indicate a possible association between the predominant expression of a V beta gene segment in lesions and the major histocompatibility complex class II haplotype of the individual. V beta 6 was prominent in the lesions of four patients who were DR15, a marker of resistance in leprosy infection. Sequence analysis of V beta 6 TCRs showed frequent use of V beta 6.1 and J beta 2.7 gene segments and a conserved amino acid motif in the V-J junction in a reversal-reaction lesion, but not in blood from the same patient. The limited TCR repertoire expressed by the infiltrating T cells suggests that a limited set of antigens is recognized in the DTH response to a human pathogen. We suggest that the mechanism by which major histocompatibility complex haplotype influences DTH in this disease involves the presentation of specific peptides, with subsequent selection of specific TCRs followed by local oligoclonal expansion.

Amino Acid Sequence↗

PubMed1993

Prevention of experimental autoimmune arthritis with a peptide fragment of type II collagen.

Collagen arthritis is induced in inbred rats with the injection of native type II collagen. The pathogenesis of this experimental autoimmune disease is T cell dependent. This study demonstrates that collagen-specific T cells, derived from pathogenic and nonpathogenic rat T cell lines, both recognize the same peptide epitope. The epitope, consisting of amino acids 58-73 of cyanogen bromide fragment 11 of type II collagen, was as effective as whole collagen in stimulating a panel of collagen-specific rat/mouse T cell hybridomas. This peptide may, therefore, constitute a dominant epitope for CD4+ rat T cells in their response to type II collagen. Administration of the peptide to either neonatal or adult rats prevented the subsequent induction of experimental arthritis with whole collagen, demonstrating that the in vivo response to this dominant epitope is, therefore, relevant in the pathogenesis of arthritis. Despite its ability to prevent collagen-induced arthritis, administration of this peptide in incomplete Freund's adjuvant intradermally did not induce disease.

Amino Acid Sequence↗

PubMed1993

B cells are anergic in transgenic mice that express IgM anti-DNA antibodies.

B lymphocytes in individuals with systemic lupus erythematosus (SLE) secrete pathogenic autoantibodies to DNA which cause clinical nephritis. (NZB X NZW) F1 (BW) female mice also secrete pathogenic anti-DNA autoantibodies, and therefore are considered to be an animal model of SLE. The rearranged immunoglobulin (Ig) genes that encode an anti-DNA antibody from a diseased BW mouse have been cloned, and transgenic (Tg) mice have been created by microinjection of these constructs into fertilized eggs from normal mice. As we reported previously, when the construct contains the C gamma 2a heavy chain constant (CH) region, the mice spontaneously secrete anti-DNA IgG and they develop mild nephritis. This demonstrated that the Ig encoded by the transgene is pathogenic. In contrast, here we report that when the construct contains the same anti-DNA Ig variable (V) regions used previously, along with the C mu region, the autoreactive B cells are rendered tolerant. Most B cells in the Tg mice express the mu transgene product on their surface, and rearrangement of endogenous light chain genes is partially suppressed. Furthermore, most hybridomas made from Tg B cells secrete IgM anti-DNA. Despite this, the Tg mice have reduced levels of total serum Ig and they do not secrete anti-DNA IgM either spontaneously or following immunization with DNA. We conclude that most B cells in the Tg mice have been rendered anergic. Anergy is however reversible in vitro; lipopolysaccharide stimulation of Tg B cells leads to the production of a significant amount of IgM anti-DNA antibody. The studies demonstrate that in this line of Tg mice on a normal mouse genetic background potentially pathogenic B cells that express a high-affinity Ig specific for a natural autoantigen are subject to tolerance by induction of anergy.

Animals↗

PubMed1993

T-cell receptor gamma delta diversity and specificity of intestinal intraepithelial lymphocytes: analysis of IEL-derived hybridomas.

The phenotype, T-cell antigen receptor (TCR) usage and specificity of intestinal intraepithelial lymphocytes (IEL), and hybridomas derived from IEL have been examined. In young conventionally reared mice, approximately 50% of the IEL express TCR alpha beta and 50% express TCR gamma delta, although there is considerable variation between individuals. Here we demonstrate that T-cell hybridomas can be prepared from freshly isolated BALB/c mouse IEL. The expressed TCR of these hybridomas reflects the TCR isotype distribution of the IEL population. Analysis of the gamma delta TCR expressed by the hybridomas demonstrates that IEL express a greater number of TCR V gene segments than has been reported for gamma delta T cells in several other epithelial sites. At least five types of gamma delta TCRs are expressed by a panel of BALB/c IEL hybridomas, although use of the gamma delta TCR V gene repertoire clearly is not random. Some TCR gamma delta cells and gamma delta hybridomas have been reported to recognize purified protein derivative (PPD); however, none of the IEL hybridomas secreted IL-2 in response to PPD. These data suggest that most TCR gamma delta IEL are not likely to be PPD reactive.

Animals↗

PubMed1993

Analysis of parathyroid hormone's principal receptor-binding region by site-directed mutagenesis and analog design.

Previous deletion studies established that the 25-34 region of PTH is important for receptor binding. We used oligonucleotide-directed mutagenesis to generate 47 different mutations in this region of human (h) PTH-(1-84) and evaluated cAMP-stimulating activity in ROS 17/2.8 cells. The hydrophobic residues Leu24 and Leu28 stood out as mutationally intolerant sites, while neighboring polar residues were comparatively tolerant. A series of synthetic PTH analogs was designed to test these residues further. The affinity of [Tyr34]hPTH-(1-34)NH2 for ROS 17/2.8 cells [dissociation constant (Kd), approximately 5 nM)] was dramatically reduced by the substitution of either Leu24 or Leu28 with Glu (Kd, approximately 20,000 and 8,000 nM, respectively). The Val31-->Glu substitution also sharply reduced affinity (Kd, approximately 200 nM). In contrast, the nearby charge-reversing change of Asp30-->Lys had no effect on binding affinity (Kd, approximately 5 nM). Similar effects were observed in the opposum kidney cell line. The binding of [Tyr34]hPTH-(15-34)NH2 to ROS 17/2.8 and opposum kidney cells (Kd, approximately 10 microM) was abolished by Glu substitutions at position 24, 28, or 31; the Lys30 change was without effect. These results suggest that the adverse effects of the Glu substitutions on receptor binding are not due purely to the disruption of tertiary interactions with the 1-14 region. Circular dichroism spectroscopy indicated that the substitutions do not affect local helical structure. The data suggest that Leu24, Leu28, and Val31 contribute important receptor-binding interactions and are consistent with the hypothesis that an amphipathic alpha-helix in the carboxy-terminal region of PTH-(1-34) is involved in receptor binding.

Amino Acid Sequence↗

PubMed1992

Failed self-tolerance and autoimmunity in IgG anti-DNA transgenic mice.

Transgenic mice were generated that express both the H and L chain genes derived from a hybridoma secreting an IgG2a mAb specific for ds- and ssDNA. This hybridoma is derived from a lupus mouse and can accelerate nephritis in young NZB x NZW F1 female mice and induce clinical nephritis in BALB/c mice. Some transgenic B cells did not exhibit allelic exclusion; they expressed both transgene-derived IgG and endogenous IgM intracellularly. Most of the B cells in transgenic mice expressed endogenous IgM, some of them expressed low levels of IgG on cell membranes. The transgenic mice, created in a strain not prone to SLE, expressed elevated serum IgG anti-DNA, and some developed clinical nephritis. The affinity of the spontaneously secreted IgG antibodies for dsDNA were similar in nephritic NZB x NZW F1 and transgenic mice. In contrast to the nontransgenic littermates, immunization of transgenic mice with murine DNA further enhanced serum levels of IgG anti-DNA in transgenic mice. Therefore, expression of transgene-encoded IgG anti-DNA mainly in the secreted form does not provide the signals necessary for allelic exclusion or self-tolerance. Expression of this Ig is sufficient to induce a mild form of autoimmune disease.

Animals↗

PubMed1992

Expression of mouse Tla region class I genes in tissues enriched for gamma delta cells.

The Tla region of the BALB/c mouse major histocompatibility complex contains at least 20 class I genes. The function of the products of these genes is unknown, but recent evidence demonstrates that some Tla region gene products could be involved in presentation of antigens to gamma delta T cells. We have generated a set of polymerase chain reaction (PCR) oligonucleotide primers and hybridization probes that permit us to specifically amplify and detect expression of 11 of the 20 BALB/c Tla region genes. cDNA prepared from 12 adult and fetal tissues and from seven cell lines was analyzed. In some cases, northern blot analysis or staining with monoclonal antibodies specific for the Tla-encoded thymus leukemia (TL) antigen were used to confirm the expression pattern of several of the genes as determined by PCR. Some Tla region genes, such as T24d and the members of the T10d/T22d gene pair, are expressed in a wide variety of tissues in a manner similar to the class I transplantation antigens. The members of the TL antigen encoding gene pair, T3d/T18d, are expressed in only a limited number of organs, including several sites enriched for gamma delta T cells. Other Tla region genes, including T1d, T2d, T16d, and T17d, are transcriptionally silent and transcripts from the T8d/T20d gene pair do not undergo proper splicing. In general, sites that contain gamma delta T lymphocytes have Tla region transcripts. The newly identified pattern of expression of the genes analyzed in sites containing gamma delta T cells further extends the list of potential candidates for antigen presentation to gamma delta T cells.

Animals↗

PubMed1992

Indication, efficiency and complications of intrathecal pump supported baclofen treatment in spinal spasticity.

In 19 patients, who suffered from severe spinal spasticity of different etiologies and did not respond sufficiently to oral antispastic therapy, intrathecal Baclofen test boli were administered. In 11 patients a DAD (Drug Administration Device) [SynchroMedR Model 8611 H, Medtronic Inc. Minneapolis, USA] was implanted. Catheter dislocation or torsion was the most common complication to be observed in these 11 patients. Long term intrathecal Baclofen application was effective in all patients, as reducing spasticity, flexor spasms and spasm induced pain. In some cases the motor performance ameliorated.

Adult↗

PubMed1992

Long-term intrathecal baclofen treatment in supraspinal spasticity.

Baclofen, a derivate of gamma-amino butyric acid (GABA), is known to be a useful drug in spasticity treatment. To achieve a good therapeutic response higher oral dosages have to be administered related with central side effects. Intrathecal application of Baclofen in microgram range dosages is proved to be effective in spinal spasticity. The efficiency of intrathecal Baclofen in patients suffering from supraspinal spasticity is discussed controversially. We report on 9 patients with long-term intrathecal Baclofen treatment, all of them responding well presenting a marked reduced muscle tone. In most cases an improvement of motor performance and in two cases improved bladder function was observed. The therapeutical dosages administered to patients with supraspinal spasticity exceed those administered to patients with spinal spasticity by approximately 100% without provoking central side effects. Despite the risks connected with this method it has to be considered as treatment of choice in cases of severe supraspinal spasticity.

Adult↗

PubMed1991

Depletion of mouse alpha beta T cell antigen receptor bearing lymphocytes by neonatal monoclonal antibody treatment.

Neonatal treatment with a monoclonal antibody specific for the alpha beta TCR results in mice with a long term, severe depletion in the number of alpha beta T cells in the periphery. Significant numbers of T cells reappear in the periphery about age 65 days, but these cells tend to lack expression of CD4 or CD8. Splenocytes of antibody-treated mice are less sensitive to mitogen stimulation or stimulation with MHC allogeneic cells. The level of serum IgG but not IgM was decreased by the treatment. Anti-alpha beta TCR antibody treatment decreased single-positive T lymphocytes that express high levels of the CD3/alpha beta TCR complex from the thymus, suggesting that the treatment could act in part by affecting negative selection of alpha beta TCR+ thymocytes. This treatment does not, however, detectably affect either the homing or the numbers of gamma delta T cells which are abundant in the intestinal epithelium, but which remain a minor population in the spleen and lymph nodes. This supports the hypothesis that gamma delta T cells are developmentally autonomous from alpha beta T cells. These mice provide an excellent model system for assessing the developmental and functional role of gamma delta T lymphocytes in vivo.

Animals↗

PubMed1991

The thymus leukemia antigen binds human and mouse CD8.

The thymus leukemia antigen (TLA) is a class Ib, or 'nonclassical' class I molecule, one of several encoded within the Tla locus of the mouse major histocompatibility complex (MHC). It structurally resembles the H-2K, D, and L class I transplantation antigens, which present processed peptides to cytotoxic T lymphocytes (CTLs). Although their function(s) are unknown, there has been recent speculation concerning the possibility that class Ib molecules may present antigens to T cells that express gamma delta T cell antigen receptors (TCRs). In this report, using both a cell-cell adhesion assay and adhesion of T lymphocyte clones to purified plate-bound TLA, we provide evidence that TLA can bind to both human and mouse CD8. We also show that a chimeric class I molecule containing the peptide antigen binding site of Ld and the alpha 3 domain, transmembrane, and cytoplasmic segments of TLA, can support a CD8-dependent immune response by CTLs. These results demonstrate for the first time binding of a class Ib molecule to CD8 with a functional outcome, as is observed for the class I transplantation antigens. The capacity to interact with CD8 has been conserved despite the extensive sequence divergence of TLA in the peptide antigen binding site, suggesting this interaction is highly significant. TLA is expressed by epithelial cells in the mouse small intestine. As these epithelial cells are in close contact with intestinal intraepithelial lymphocytes that are nearly all CD8+, and many of which express the gamma delta TCR, the data are consistent with the hypothesis that TLA is involved in antigen presentation, perhaps to gamma delta-positive lymphocytes in this site.

Amino Acid Sequence↗

PubMed1991

Self-tolerance and autoimmunity.

Studies of self-tolerance and autoimmunity have moved rapidly into new arenas. These include the definition of at least two mechanisms for tolerance induction in both T and B cells, the creation of new disease-susceptible strains such as the HLA-B27 transgenic rats, the creation of new disease-resistant strains such as I-E or I-Ak NOD transgenic mice, and the precise definition of both antigen and antigen receptor for pathogenic lymphocytes in some models. More effective therapies for autoimmune disease should result from the knowledge gained.

Animals↗

PubMed1991

Analysis of MHC class I gene expression in adult bone marrow and fetal liver of the BALB/c mouse.

The BALB/c mouse has at least 29 class I genes encoded in the Qa, Tla, and Hmt (histocompatibility dependent on a maternally transmitted factor) regions of the MHC. The pattern of expression of these class Ib MHC genes is not well characterized, although some of their products such as the serologically detectable Qa-2 and TL Ag are expressed mainly in lymphoid and hematopoietic tissues. In this study, the expression pattern of BALB/c class I genes has been analyzed in adult bone marrow and fetal liver. cDNA libraries were synthesized from these tissues, and isolated class I cDNA clones were characterized by hybridization with oligonucleotide probes and by nucleotide sequence analysis. Of the 29 total class Ib genes, transcripts of five including Q6d, Q7d, T9c, T10c, and the 37 gene were isolated from the bone marrow cDNA library. Four of these can encode proteins; the sequence of the T10c gene demonstrates it is most likely a pseudogene. A non-overlapping set of three class Ib cDNA clones was obtained from the fetal liver, including T13c, the Thy 19.4 gene, and a previously uncharacterized class I gene provisionally designated as FL 57.2. Although the majority of H-2Dd cDNA clones that were analyzed lack introns, many of the class Ib cDNA clones contain intron sequences. This suggests that the expression of some of these genes may be regulated at the level of RNA splicing. The T13c gene encodes the thymus leukemia Ag in BALB/c mice. We have confirmed that the T13c gene is expressed in fetal liver by flow cytometric analysis of cells stained with anti-TL mAb.

Animals↗

PubMed1991

Characterization of a CD4-positive T-cell line derived from an athymic (nu/nu) mouse.

We have isolated a Thy-1+, CD3+, CD4+ T-cell line from the spleen of a 12-week-old nu/nu (nude) BALB/c mouse. The cell line is clonal, and it expresses an alpha beta T-cell antigen receptor. Upon activation, these cells secrete IL-2 but not IL-4, putting them in the Th1 category. The cells can be triggered to proliferate and secrete lymphokines in the presence of irradiated syngeneic or allogeneic splenic feeder cells that express a variety of MHC haplotypes. This response is MHC class II-specific, because it can be blocked by either anti-Ia or anti-CD4 antibodies. From the response pattern of this T-cell line, we conclude that it recognizes a common determinant on class II MHC antigens. This nude mouse T-lymphocyte presumably has not undergone thymic selection. Therefore its unique specificity may reflect both the bias of T-cell antigen receptor genes for encoding receptors that recognize MHC molecules and the requirement for functional thymic epithelial cells for the efficient education of a self-MHC-restricted repertoire.

Animals↗