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Biomedical subjects

D A Carson

Publications and source records attributed to D A Carson.

At least 163 records · Page 9Linked to original sources
PubMed1990

Transforming growth factor beta and noncytopathic mechanisms of immunodeficiency in human immunodeficiency virus infection.

This study examines the contribution of transforming growth factor beta (TGF beta), one of the most potent endogenous immunosuppressive factors, to the development of immunodeficiency in human immunodeficiency virus (HIV) infection. Increased titers of TGF beta were found in supernatants of peripheral blood mononuclear cells (PBMCs) from HIV-infected donors as compared to uninfected controls (P less than 0.001). This correlated closely with defective responses of CD4+ lymphocytes to the recall antigens tuberculin purified protein derivative or tetanus toxoid. The addition of TGF beta-neutralizing antibody to PBMCs partially restored these defective T-cell responses. Furthermore, purified TGF beta or HIV+ PBMC culture supernatants preferentially inhibited proliferation of CD4+ lymphocytes as compared to CD8+ cells. The increased expression of the TGF beta protein was associated with increased TGF beta mRNA as determined by a polymerase chain reaction assay. This increase in TGF beta protein and mRNA was due to a selective upregulation of the TGF beta 1 isoform. These results indicate that overexpression of TGF beta 1 occurs in HIV-infected individuals and that this cytokine can contribute to impaired immune functions and to depletion of CD4+ T lymphocytes.

Acquired Immunodeficiency Syndrome↗
PubMed1990

The early expression of some human autoantibody-associated heavy chain variable region genes is controlled by specific regulatory elements.

Recent molecular cloning studies have revealed that some autoantibodies may be encoded directly by germline Ig variable (V) genes without any somatic mutation, suggesting strongly that such autoantibodies are physiologically important. Independent analyses of Ig gene expression in a human fetal liver showed that only nine heavy chain V (Vh) genes were used, out of a potential germline Vh gene repertoire of 100-200. We have observed that four of these nine Vh genes encode sequences identical or almost identical to human autoantibody heavy chains. This unexpected overlap implies that some autoantibodies are expressed preferentially during early development. Recent structural analyses of two Vh3 genes expressed in fetal liver revealed many more enhancer-like sequences in the flanking regions than expected for a typical Vh gene. It is hypothesized that these autoantibody-related Vh genes may contain various combinations of cis regulatory elements which influence their specific expression during early ontogenic development. Furthermore, these observations are consistent with network hypotheses, which suggest that early B-cell development is driven by reactivity with self. The cis regulatory elements in the autoantibody genes may act in concert with the positional effects that have been shown to facilitate Vh gene engagement.

Animals↗
PubMed1990

Potent toxicity of 2-chlorodeoxyadenosine toward human monocytes in vitro and in vivo. A novel approach to immunosuppressive therapy.

Lymphoid cells were thought to be uniquely susceptible to excess 2'-deoxyadenosine (dAdo), when exposed to inhibitors of adenosine deaminase (ADA). However, we now find that human monocytes are as sensitive as lymphocytes to dAdo or to the ADA-resistant congener 2-chloro-2'-deoxyadenosine (CldAdo). Monocytes exposed in vitro to CldAdo, or to dAdo plus deoxycoformycin rapidly developed DNA strand breaks. Both the DNA damage and the toxicity of CldAdo or dAdo toward monocytes were blocked by deoxycytidine, but not by inhibitors of poly(ADP-ribose) polymerase. A partial decrease in RNA synthesis and a gradual decline of cellular NAD were early biochemical events associated with monocyte DNA damage. Low CldAdo concentrations (5-20 nM) inhibited monocyte phagocytosis and reduced the release of interleukin 6. Higher CldAdo concentrations led to a dose- and time-dependent loss of monocyte viability. Circulating monocytes disappeared within 1 wk in patients with cutaneous T cell lymphoma or with rheumatoid arthritis during continuous CldAdo infusion. The marked sensitivity of human monocyte function and survival to CldAdo in vitro, together with the monocyte depletion in patients receiving CldAdo chemotherapy, suggests that CldAdo or other dAdo analogues offer a novel therapeutic strategy for chronic inflammatory and autoimmune diseases characterized by inappropriate monocyte deployment or function.

2-Chloroadenosine↗
PubMed1990

Cold agglutinins: specificity, idiotypy and structural analysis.

Cold agglutinins likely represent natural autoantibodies with precursors that arise early during ontogeny. Many use L chains derived from the germline kv325 gene, in association with H chains derived from the VHIV gene family. CAs probably represent an expression of the preimmune repertoire. The appearance of CAs in a variety of disorders may be due to the prevalence of CA B cell precursors, and the ubiquity of their target epitopes. CAs may arise independent of antigenic selection during Epstein-Barr virus infection in response to the expansion of immature B cells. In support, L chains bearing the markers for the kv325 gene are preferentially expressed during in vitro and in vivo Epstein-Barr virus infection. Certain CAs that arise in lymphoproliferative disorders represent a clonal expansion, produced by karyotypically abnormal lymphocytes. As such, antigenic selection may foster the early expansion of CA-producing clones. These cells are later more prone to become autonomous, and overt malignancy may then occur. Clues to the genetic origin of these antibodies are now being appreciated, but further study will be required to understand the defects responsible for the transformation of a natural autoantibody into a malignancy.

Agglutinins↗
PubMed1990

CD5-positive B-cell malignancies frequently express cross-reactive idiotypes associated with IgM autoantibodies.

Using monoclonal antibodies (MAb) specific for cross-reactive idiotypes (CRIs) associated with human monoclonal IgM autoantibodies, we examined 57 biopsy specimens that previously had been noted to have immunohistologic features of CD5-positive B-cell small lymphocytic (SL) non-Hodgkin's lymphoma (NHL). Twenty-five lymphoma specimens were noted to be from patients with chronic lymphocytic leukemia (CLL). Eight of thirty-four (24%) immunoglobulin (Ig) kappa light-chain expressing lymphomas reacted with 17.109, a MAb specific for a major CRI encoded by a conserved Ig kappa variable region gene (Vk gene) of the VkIIIb sub-subgroup. All 17.109-reactive tissues and two 17.109-negative specimens were recognized by another MAb specific for VkIIIb framework determinant(s). Seven of all fifty-six (13%) Ig-expressing tumors bound G6, a MAb specific for an autoantibody heavy-chain-associated CRI that is encoded by a conserved antibody heavy chain variable region gene(s) (VHgene) of the VH1 subgroup. All seven G6-positive lymphomas and two G6-negative tumors reacted with Cc1, another MAb specific for a rheumatoid factor heavy-chain-associated CRI. A third autoantibody-heavy-chain-associated CRI, termed Lc1, was expressed by seven (13%) other lymphomas. Finally, a fourth MAb specific for RF heavy-chain-associated CRI, named B6, detected two additional tumors. The expression frequencies of autoantibody-associated CRIs among SL NHL patients without peripheral lymphocytosis did not differ from those noted among patients with CLL but were significantly higher than those observed among patients with NHL of follicular center-cell origin. These data imply that the malignant B cells of patients with either CD5-positive B-cell SL NHL or CLL express a restricted set of Ig V genes that have not substantially diversified from the germline DNA.

Antibodies, Monoclonal↗
PubMed1989

Poly(ADP-ribose) polymerase inhibits DNA synthesis initiation in the absence of NAD.

Poly(ADP-ribose) polymerase (ADPRP) is a nuclear enzyme that transfers ADP-ribose from NAD+ to diverse nuclear proteins. Previously, the function of ADPRP was considered to relate exclusively to its catalytic activity. However, recent experiments have shown that ADPRP is actually an abundant DNA-binding protein, and that the potential catalytic activity of the enzyme is more than 100-fold greater than the measured rates of NAD+ turnover in intact cells. To better understand the role of ADPRP, we have used highly purified ADPRP and a monospecific autoantibody to examine the effects of ADPRP on in vitro DNA synthesis in the presence or absence of NAD+ substrate. The data show that DNA synthesis initiation is blocked by ADPRP and that auto-poly (ADP-ribosyl)ation reverses the process by diminishing the DNA binding capacity of the protein. These results suggest that ADPRP actually is a structural DNA binding protein, whose catalytic activity serves to modulate its interaction with DNA.

Animals↗
PubMed1989

Characterization of four homologous L chain variable region genes that are related to 6B6.6 idiotype positive human rheumatoid factor L chains.

A significant proportion of monoclonal IgM rheumatoid factors (RF) from patients with mixed cryoglobulinemia express a KIIIa L chain-associated cross-reactive idiotype, termed 6B6.6. Previously, we reported the isolation from a patient with a monoclonal RF of a Vk gene, termed Humkv328, whose deduced amino acid sequence differs by three and seven residues from the L chains of the 6B6.6-positive RF Les and Pom, respectively. To further delineate the genetic basis of the 6B6.6 cross-reactive idiotype, we isolated from the same patient another Vk gene, termed Humkv329, which differs from kv328 by only three bases over a stretch of 1331 nucleotides sequenced. However, kv329 has a stop codon at amino acid position 94, and is thus a pseudogene. Therefore, we screened a second genomic library from an unrelated individual and isolated two potential function Vk genes (i.e., Humkv328h2 and Humkv328h5) which are highly homologous to Humkv328. All three potential functional Vk genes differ from each other by one to six bases over a 1331-bp stretch and all encode the same Vk region amino acid sequence. Among the six bases by which Humkv328h5 differs from Humkv328, two are in the conserved pentadecanucleotide region, which is known to be important in the regulation of k L chain transcription. In the future it will be important to ascertain the potential association of polymorphisms in the conserved pentadecanucleotide region with RF associated autoimmune and lymphoproliferative diseases.

Amino Acid Sequence↗
PubMed1989

Bacterial lipopolysaccharide and inflammatory mediators augment IL-6 secretion by human endothelial cells.

The interaction between human endothelial cells and leukocytes during immunologic and inflammatory responses is in part mediated through the release of soluble mediators. We report that cultured human umbilical vein endothelial cells secrete IL-6 when stimulated with LPS. This effect was inhibited by polymyxin-B. The monokines IL-1 and TNF-alpha were also potent inducers of IL-6, whereas lymphotoxin was only effective at much higher concentrations. Endothelial cell supernatant IL-6 was active as hybridoma-plasmacytoma growth factor and as B-cell stimulating factor. Endothelial IL-6 activity was neutralized by a specific anti-IL-6 antibody and by immunoprecipitation it was shown to be identical in size to human fibroblast-derived IL-6. As IL-6 is possibly an important regulator of host defense responses, production of this cytokine by endothelial cells may contribute to the pathogenesis of various inflammatory and immunologic diseases.

Adjuvants, Immunologic↗
PubMed1989

Characterization of two immunoglobulin VH genes that are homologous to human rheumatoid factors.

We isolated a VH1 germline gene (Humhv1263) that is closely related to the heavy chains of 2 human rheumatoid factors (RF), Bor and Kas. We also found that the 783 rearranged VH1 gene is actually 91-93% homologous to Bor and Kas, and it differs from a VH1 complementary DNA (51P1) by only a single base. Thus, 783 is likely to be the unmutated form of a germline VH gene that may encode the heavy chains of RF Bor and Kas and several other human monoclonal RF.

Amino Acid Sequence↗
PubMed1989

Utilization of 2'-deoxynad for ADP-ribose transfer reactions.

2'-deoxyNAD was examined as a substrate for both mono(ADP-ribosyl)ation and poly(ADP-ribosyl)ation reactions. 2'-deoxyNAD is a substrate for the diphtheria toxin-catalyzed mono(ADP-ribosyl)ation of elongation factor-2, inactivating its function to enhance protein synthesis. On the other hand, 2'-deoxyNAD is a poor substrate for poly(ADP-ribose) polymerase. 2'-deoxyNAD was not synthesized intracellularly from deoxyATP, even when deoxyATP content was markedly increased by incubation of cells with deoxyadenosine and an adenosine deaminase inhibitor. 2'-deoxyNAD, because of its specificity, could be a quite useful reagent for the investigation of cellular mono(ADP-ribosyl)ation reactions.

ADP Ribose Transferases↗
PubMed1989

Profound toxicity of deoxyadenosine and 2-chlorodeoxyadenosine toward human monocytes in vitro and in vivo.

Deoxyadenosine is known to be toxic to both proliferating and resting lymphocytes that lack adenosine deaminase (ADA) activity. We now show that human monocytes are also highly sensitive in vitro to nanomolar concentrations of deoxyadenosine plus the ADA inhibitor deoxycoformycin, and to the ADA-resistant analogue 2-chlorodeoxyadenosine (CdA). Monocytes exposed to deoxyadenosine or to CdA in vitro accumulate massive DNA damage detectable within 1 hour. The DNA damage in monocytes exposed to CdA is associated with a decrease in protein synthesis and with inhibitions of phagocytosis and IL-6 secretion. However, unlike lymphocytes with similar DNA damage, the monocytes show no significant NAD or ATP depletion until cell viability declines. The selective toxicity of CdA to monocytes was confirmed by in vivo studies. In almost all patients receiving CdA infusion chemotherapy for cutaneous lymphoma, the blood monocytes counts fell to near 0 during one week of therapy. Our results suggest that CdA and related compounds may have potential clinical use in the therapy of immune disorders associated with monocyte/macrophage activation.

2-Chloroadenosine↗