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Biomedical subjects

D A Carson

Publications and source records attributed to D A Carson.

At least 307 records · Page 17Linked to original sources
PubMed1983

The internal image of IgG in cross-reactive anti-idiotypic antibodies against human rheumatoid factors.

A network of idiotypes and anti-idiotypes has been hypothesized to modulate antibody production against exogenous antigens. Idiotypic antigens on autoantibodies have been studied because of their potential use for specific immunomodulation. The present studies describe the preparation and characterization of rabbit anti-idiotypic antibody against human IgM anti-IgG autoantibodies (rheumatoid factors, RF) that bear the "internal image" of the human IgG-Fc fragment, and hence react specifically with the majority of RF from patients with rheumatoid arthritis. The anti-idiotype was isolated from rabbit anti-RF antisera by either immunodepletion of anti-immunoglobulin antibodies, or more simply by a single affinity purification step on a rabbit anti-human IgG Fc column. As measured by an enzyme-linked immunoassay, the anti-idiotype prepared by both methods bound to plates coated with purified IgM RF, but not to plates coated with non-RF IgM proteins. The anti-idiotype dose dependently blocked the binding to IgG of IgM-RF in 83% of sera from multiple patients with rheumatoid arthritis, Sjogren's syndrome, and macroglobulinemia. The anti-idiotype did not inhibit the activity of human IgM antibodies against DNP, tetanus toxoid, or thyroglobulin. The antigen recognized by the cross-reactive anti-idiotype was not apparently associated with a particular light or heavy chain amino acid sequence, but rather was intrinsic to most immunoglobulins with RF activity. Broadly cross-reactive anti-idiotypes with the "internal image" of IgG are simple to generate, and react with most RF. They may facilitate studies on the specific regulation of the human anti-IgG autoantibody response.

Animals↗
PubMed1982

Activation of the classical pathway of complement by rheumatoid factors. Assessment by radioimmunoassay for C4.

A simple, sensitive solid-phase radioimmunoassay to quantitate the activation of the classical pathway of complement by rheumatoid factor (RF) is described. RF (purified, in serum or synovial fluid) was bound to reduced and alkylated IgG adsorbed to polyvinyl chloride microtiter plates and reacted with diluted normal human serum (complement). The activation and binding of C4 were quantitated with 125I-Fab'2-anti-C4. Purified, polyclonal IgM--RF was 100- to 1,000-fold more effective than purified IgG--RF in activating complement. The amount of complement activation produced by RF in each of the 57 sera and 2 synovial fluid samples correlated directly with the amount of IgM--RF present. The complement activating abilities of polyclonal IgM--RF in the sera of 15 rheumatoid arthritis patients were homogeneous. This novel technique is readily applicable to the investigation of complement activation by RF in disease.

Animals↗
PubMed1982

Frequencies of Epstein-Barr virus-inducible IgM anti-IgG B lymphocytes in normal children and children with juvenile rheumatoid arthritis.

The relative frequencies of IgM antiIgG autoantibody (rheumatoid factor) producing cells induced by the polyclonal B cell activator Epstein-Barr virus were measured in peripheral blood lymphocyte cultures of normal children and patients with juvenile rheumatoid arthritis. The frequencies of rheumatoid factor precursor B cells in normal children were lower than adults, but higher than neonates. The frequency increased with the age of the donor. In seronegative children with the systemic-onset or pauciarticular-onset types of juvenile rheumatoid arthritis, the number of IgM antiIgG inducible B cells was not significantly different (P greater than 0.05) from age-matched controls. Patients with seropositive juvenile rheumatoid arthritis or seropositive adult rheumatoid arthritis had significantly higher IgM antiIgG precursor cell frequencies than age-matched normal subjects (P less than 0.01 and P less than 0.02, respectively). In contrast, the patients with seronegative polyarticular-onset juvenile rheumatoid arthritis had an average precursor frequency significantly lower than normal age-matched controls (P less than 0.05), analogous to results previously noted in adult seronegative rheumatoid arthritis. Thus, both children and adults with seronegative polyarticular rheumatoid arthritis had a deficiency in B cells that produce IgM antiIgG and that are induced by Epstein-Barr virus. This distinguished them from seropositive juvenile rheumatoid arthritis and rheumatoid arthritis patients, normal subjects, and patients with the pauciarticular-onset and systemic-onset types of seronegative juvenile rheumatoid arthritis.

Adolescent↗
PubMed1982

Possible metabolic basis for the different immunodeficient states associated with genetic deficiencies of adenosine deaminase and purine nucleoside phosphorylase.

An inherited deficiency of adenosine deaminase (Ado deaminase; adenosine aminohydrolase, EC 3.5.4.4) causes severe combined immunodeficiency disease in humans. A similar deficiency in purine nucleoside phosphorylase (Puo phosphorylase; purine-nucleoside:orthophosphate ribosyltransferase, EC 2.4.2.1) engenders a selective cellular immune deficit. To elucidate the possible metabolic basis for the contrasting immunologic phenotypes, we compared the toxicity toward mature resting human lymphocytes of the Ado deaminase substrates deoxyadenosine and adenosine and the Puo phosphorylase substrate deoxyguanosine. When Ado deaminase was inhibited, micromolar concentrations of deoxyadenosine progressively killed nondividing helper and suppressor-cytotoxic T cells, but not B cells. The toxicity required phosphorylation, with subsequent dATP formation. The deoxyadenosine analogs 2-chlorodeoxyadenosine, 2-fluorodeoxyadenosine, and adenine arabinonucleoside also killed resting T cells. Cell death was unrelated to inhibition of adenosylhomocysteinase (EC 3.3.1.1) but was preceded by a gradual decline in ATP levels. As much as 1 mM deoxyguanosine did not impair resting lymphocyte viability, despite the synthesis of dGTP. The combination of 200 microM adenosine plus 500 microM homocysteine thiolactone killed dividing lymphocytes but had no discernible toxic effect toward resting T cells, which accumulated adenosylhomocysteine over a 4-hr period but thereafter excreted the nucleoside into the culture medium. The different clinical syndromes associated with genetic deficiencies of Ado deaminase and Puo phosphorylase may be explained by the ability of dATP to kill mature resting T lymphocytes by depleting ATP levels.

Adenosine↗
PubMed1982

Membrane antigen on Epstein--Barr virus-infected human B cells recognized by a monoclonal antibody.

This paper describes a monoclonal antibody (B532) that detects a membrane antigen present on greater than or equal to 95% of the B cells from lines carrying the Epstein-Barr virus (EBV) genome. Evidence suggesting that B532 is EBV-related was originally obtained by using a cell-binding radioassay with different cell line substrates. Immunofluorescence and cell-sorter analysis confirmed that the antigen was present in high density on all EBV-infected lymphoblastoid B-cell lines, but not on EBV-negative B-, T-, myeloid, or null cell lines. Isolated normal peripheral blood B and T lymphocytes and monocytes failed to bind B532. The monoclonal antibody did not inhibit in vitro EVB infection nor did it block the killing of EBV-infected targets by cytotoxic T lymphocytes. The cell surface antigen recognized by B532 was shown by immunoprecipitation to have a molecular weight of approximately 45,000.

Animals↗
PubMed1982

Differential cyst(e)ine requirements in human T and B lymphoblastoid cell lines.

In an effort to find exploitable metabolic differences between human T and B lymphoblasts, we have compared the ability of lymphocytes of varying phenotype to grow in cystine-deficient medium. Only 6 of 12 human lymphoblastoid cell lines tested were able to utilize homocysteine thiolactone or cystathionine in place of cystine for growth. This difference in growth requirements was unrelated to the rate of cell division, the presence of Epstein-Barr viral genetic material, or whether or not the cell lines derived from benign or malignant tissues. Rather, all B lymphoblastoid cell lines grew in homocysteine thiolactone- or cystathionine-containing medium, while the T and non-T, non-B lymphoblastoid cell lines did not. Normal human peripheral blood T and B lymphoblasts did not respond to mitogens in the homocysteine thiolactone or cystathionine medium, but developed the ability to utilize these cysteine precursors after stimulation with concanavalin A, protein A, or Epstein-Barr virus. The differences in cysteine requirements among T and B cell lines may reflect a fundamental difference in de novo protein-synthesizing capacity of the two cell types.

B-Lymphocytes↗
PubMed1982

[Rheumatoid factors].

Rheumatoid factors (FRs) are auto antibodies which react with different antigenic sites on the Fc piece of human IgG. They appear in large amounts in serum and synovial fluid of patients with rheumatoid arthritis (RA) but they are not specific to this disease. Different methods of detection have been proposed but they induce a low threshold of sensibility and regularly give rise to a low specificity for RA diagnosis. Those auto antibodies have a weak affinity for their antigen. However, despite this weak affinity, they contribute to the formation of large and stable articular immune complexes which could induce inflammatory synovial processes during RA. Occurrence of RFs during various infectious diseases is an argument for a protective role of RFs. This protective role is supported by the findings that RFs structural genes are largely distributed in normal populations and, in part, inherited, and that normal peripheral blood lymphocytes are able to make IgM FR when in vitro polyclonally stimulated.

Arthritis, Rheumatoid↗
PubMed1982

Selective induction of autoantibody secretion in human bone marrow by Epstein Barr virus.

The bone marrow is an important site for B lymphocyte differentiation and antibody synthesis in animal and man. However, few experiments have examined directly its immunologic functions in humans. In the present experiments, we have induced bone marrow B lymphocytes from human donors with degenerative arthritis of varying ages to secrete two autoantibodies, IgM and anti-IgG (rheumatoid factor) and IgM anti-human thyroglobulin (Tg), by stimulation with the polyclonal B cell activator Epstein Barr virus (EBV). The EBV-stimulated bone marrow cells secreted significantly more IgM anti-IgG (p less than 0.01) and IgG anti-Tg (p less than 0.01) than matched, identically treated peripheral blood cells. Bone marrow cultures from donors over the age of 60 yr, particularly females, produced more rheumatoid factor than cultures from younger donors (p less than 0.01). The EBV-inducible autoantibodies were immunospecific as demonstrated by adsorption studies. A potential pathogenic role in the inflammatory process was suggested by the finding that the EBV-inducible IgM anti-IgG autoantibodies were capable of activating the classical complement pathway as assessed by the cleavage of C4. These results indicate that the human bone marrow is a selective reservoir for EBV-inducible autoantibody precursor B lymphocytes, and that the size of the reservoir increases with age.

Adult↗
PubMed1982

Characterization of an adenosine 5'-triphosphate- and deoxyadenosine 5'-triphosphate-activated nucleotidase from human malignant lymphocytes.

The kinetic properties of a soluble, magnesium-dependent 5'-nucleotidase from human malignant lymphocytes have been determined. The partially purified enzyme is distinct from plasma membrane-associated 5'-nucleotidase and is free of nonspecific phosphatase activity. Among purine ribonucleotides, it reacted efficiently with inosine 5'-monophosphate and guanosine 5 -monophosphate and to a lesser degree with deoxyguanosine 5'-monophosphate. Adenosine 5'-monophosphate and deoxyadenosine 5'-monophosphate were 30-fold less efficient substrates. Increasing concentrations of adenosine 5'-triphosphate and deoxyadenosine 5'-triphosphate from 0 to 3 mM enhanced 5'-nucleotidase activity up to 7-fold. Guanosine 5'-triphosphate and deoxyguanosine 5'-triphosphate were much less effective enzyme activators, while uridine 5'-triphosphate was without effect. Inorganic phosphate inhibited dephosphorylating activity in both adenosine 5'-triphosphate-supplemented and unsupplemented buffer. The activation of this 5'-nucleotidase by deoxyadenosine 5'-triphosphate, combined with the relative inability of the enzyme to dephosphorylate deoxyadenosine 5'-monophosphate, conceivably may contribute to the adenine nucleotide degradation induced by deoxyadenosine in normal and malignant lymphocytes.

5'-Nucleotidase↗
PubMed1982

Deficiency of methylthioadenosine phosphorylase in human leukemic cells in vivo.

Cells from 20 patients with leukemia and 9 with solid tumors were assayed for the enzyme methylthioadenosine phosphorylase, which function in both purine and polyamine metabolism in rapidly dividing cells. As determined by autoradiography of viable cells, and by direct enzymatic analysis, samples from one individual with pre-T-cell acute lymphoblastic leukemia and one with common acute lymphoblastic leukemia were methylthioadenosine phosphorylase deficient. In contrast, other leukemias of similar antigenic phenotype, as well as normal peripheral blood lymphocytes, thymic lymphocytes, and normal bone marrow cells, had substantial methylthioadenosine phosphorylase activity. This evidence suggests that the complete absence of methylthioadenosine phosphorylase distinguishes some leukemic cells in vivo from their nonmalignant counterparts.

Adolescent↗
PubMed1981

Dependence of adenine production upon polyamine synthesis in cultured human lymphoblasts.

The exact source of de novo adenine produced by mammalian cells remain poorly understood, and this prompted the present study. Using a human lymphoblastoid cell line (WI-L2) deficient in adenine phosphoribosyltransferase (EC 2.4.2.7), we have quantitated the rate of adenine synthesis and the relative importance of the phosphorolysis of 5'-methylthioadenosine versus adenosine or 2'-deoxyadenosine in adenine generation. Dividing adenine phosphoribosyltransferase-deficient WI-L2 cells produced adenine at a rate of 0.27 nmol/mg protein/h. This represented approximately 10% of the rate of hypoxanthine production by WI-L2 cells deficient in hypoxanthine phosphoribosyltransferase (EC 2.4.2.8) but was equivalent to the rate of 5'-methylthioadenosine synthesis by human lymphoblastoid CCRF-CEM deficient in 5'-methylthioadenosine, phosphorylase (5'-methylthioadenosine: orthophosphate methylthioribosyltransferase). Up to 97% of adenine, but not hypoxanthine, synthesis was inhibited dose-dependently by the S-adenosylmethionine decarboxylase-inhibitor methylglyoxal bis(guanylhydrazone) and also by spermidine and spermine, but was enhanced by putrescine. The addition of 2-fluoroadenine, a potent competitive inhibitor of methylthioadenosine phosphorylase (Ki = 0.43 microM) to adenine phosphoribosyl-transferase-deficient cells resulted in a progressive accumulation of 5'-methylthioadenosine in the culture medium, and up to an 85% decrease in adenine production at non-toxic concentrations. These results show that de novo adenine synthesis by dividing human cells is considerable, and that 85-97% derives from the cleavage of 5'-methylthioadenosine and hence from polyamine synthesis.

Adenine↗