Search PubMed⌕ Search

Biomedical subjects

D K Cooper

Publications and source records attributed to D K Cooper.

At least 109 records · Page 6Linked to original sources
PubMed1996

Monoclonal antiidiotypic antibodies neutralize cytotoxic effects of anti-alphaGal antibodies.

The aims of this study were to produce and characterize mouse monoclonal antiidiotypic antibodies (AIAs) that specifically bind human antipig (anti-alphaGal) antibodies and to select those AIAs that neutralize the cytotoxicity of human or baboon serum to pig (PK15) cells. Mice were immunized with human anti-pig antibodies, and hybridomas were produced using conventional techniques. From a total of 480 clones, 11 produced AIAs that bound with high affinity to human anti-alpha Gal IgG and F(ab')2 fragments, and individually reduced serum cytotoxicity to pig cells by 40 - 90%. Seven of the AIAs also bound to human peripheral B lymphocytes (that express the same idiotypes as the antibodies produce). Several combinations of two or three AIAs provided 100% protection of PK15 cells. Selected AIAs injected intravenously into baboons reduced the cytotoxicity of subsequently drawn sera by 50--80% for >48 hr. The cytotoxicity studies also indicated that there are at least two dominant idiotypes expressed in the human anti-alphaGal population. We conclude that AIAs against anti-alphaGal antibodies could be successfully used in 1) preoperative characterization of a recipient's anti-alphaGal profile, (2) prevention of hyperacute rejection of a pig organ, and (3) specific immunosuppression through elimination of anti-alphaGal-producing B lymphocytes.

Animals↗
PubMed1996

Cobra venom factor stimulates anti-alpha-galactose antibody production in baboons. Implications for pig-to-human xenotransplantation.

Cobra venom factor (CVF) depletes complement and may therefore be of use in preventing the hyperacute rejection that follows discordant organ xenotransplantation. In two baboons studied, the intramuscular injection of CVF (0.25 mg/kg) was followed by a marked reduction in serum C3 and CH50, and serum cytotoxicity to pig kidney (PK15) cells. There was, however, a very rapid rise in the level of anti-alpha-galactose (alpha Gal) antibody, and a slower rise in anti-CVF antibody. A second intramuscular injection of CVF on day 14 was ineffective in reducing C3, CH50, and serum cytotoxicity. The major oligosaccharide of CVF is known to contain alpha Gal residues, which we suggest stimulate the major increase in anti-alpha Gal antibody level seen in the present study. In the clinical situation, this might lead to an increased immune response to a concomitantly transplanted pig organ.

Animals↗
PubMed1996

Xenotransplantation--state of the art.

Organ transplantation is limited by the number of cadaveric human donor organs that become available. Xenotransplantation--the transplantation of organs and tissues between animal species--would supply an unlimited number of organs and offer many other advantages. The pig has been identified as the most suitable donor animal. Pig organs, when transplanted into humans or nonhuman primates, are, however, rejected hyperacutely within minutes by antibody-mediated complement activation. Human anti-pig antibodies have been identified as being directed against Gal alpha1-3galactose epitopes on pig vascular endothelium. Major efforts are being made to overcome this hyperacute rejection. Methods being investigated include (i) depletion or inhibition of recipient antibodies or complement, (ii) development of transgenic pigs that do not express the alphaGal epitope and/or express a human complement inhibiting protein (e.g. DAF), and (iii) development of immunological tolerance to pig organs in the recipient. If complement activation is prevented, e.g. by inhibition of complement activation by cobra venom factor, soluble complement receptor 1 or by the use of hDAF transgenic pig organs, then "delayed xenograft rejection" occurs and is again believed to be largely antibody-dependent. Experimental pig-to-primate organ xenotransplantation is now, however, resulting in transplant function for days and weeks rather than minutes, and there is therefore optimism that we are on the threshold of a new era in the field of the transplantation of vital organs.

Animals↗
PubMed1996

Characterization of baboon class I major histocompatibility molecules. Implications for baboon-to-human xenotransplantation.

Increasingly strong medical and political pressures are stimulating consideration of the transplantation of baboon organs and cells into humans. Critical to the success of these xenotransplants is management of the immune system such that graft rejection and, in the case of bone marrow transplantation, graft-versus-host disease do not result in transplant failure. The polymorphic products of the major histocompatibility complex (MHC) are the primary barrier to successful allotransplantation, and here we describe class I MHC molecules from baboon (Papio anubis) to gain an understanding of how similarities and differences between baboon and human MHC molecules might affect xenograft survival and function. Comparative analyses of our five novel baboon class I molecules with defined HLA class I molecules demonstrate that the baboon class I molecule are up to 90% identical. Disparity between baboon class I proteins and their human homologues lies predominately at positions in the antigen-binding groove, while C-terminal portions of the class I heavy chain are more conserved between the two species. Such concentration of cross-species differences within the alpha1 and alpha2 domains involves a majority of substitutions at positions demonstrating polymorphism in human alleles; the location of substitutions distinguishing baboon and human molecules thus resembles the positioning of human class I allopolymorphisms. Because this preliminary characterization indicates that both baboon and human T cells with be restricted by xenogeneic class I molecules, immune responses triggered during baboon-to-human transplantation should mimic those arising during MHC mismatched human allotransplantation.

Amino Acid Sequence↗
PubMed1996

How many endomyocardial biopsies are necessary in the first year after heart transplantation?

Since 1989, the immunosuppressive regimen used in all heart transplant (HTx) patients at our center has consisted of a combination of cyclosporin, azathioprine, and prednisone. No prophylactic cytolytic agents have been given. One hundred consecutive patients were followed for periods of 4-56 months (mean 27 months). The incidence of rejection was so low in the initial 18 patients that we felt confident about reducing the number of routine endomyocardial biopsies (EMBs) that were performed. The mean number of EMBs in this subgroup was 10 (median 11). In the next 20 patients, EMB was performed routinely on only three occasions during the 1st post-transplant year (at 2, 4, and 8 weeks). In the subsequent 62 patients, EMB was performed on post-transplant days 10, 20, 30, and 60. Further EMBs were performed after acute rejection episodes had been treated. No noninvasive methods of diagnosing rejection were employed. In 82 consecutive patients, therefore, the mean number of EMBs within the 1st year was five per patient (median four), with 58% undergoing fewer than five EMBs and 25% requiring more than five EMBs. In the entire group of 100 patients, the mean number of EMBs was 5.9. The incidence of acute rejection requiring increased therapy was 24%. Only 7% required i.v. steroids, two of whom (2%) also required ALG and/or OKT3, with 17% requiring increased oral immunosuppression alone. Actuarial survival was 98% at 30 days, 94% at 1 year, and 92% at 2 years. It is possible that we may have missed acute rejection episodes that resolved spontaneously. However, the excellent medium-term results would suggest that any such rejection episode did not progress to become hemodynamically significant. It may be, therefore, that when an effective immunosuppressive regimen is utilized, the number of EMBs performed at many centers is excessive.

Adolescent↗
PubMed1996

The reducing end of alpha Gal oligosaccharides contributes to their efficiency in blocking natural antibodies of human and baboon sera.

Synthetic galactosyl oligosaccharides were tested for their ability to inhibit the cytotoxic reaction of human and baboon natural antibodies on PK15 cells in culture. Methyl-alpha-Gal gave weak inhibition, Gal alpha 1-3Gal substantially inhibited the reaction (400muM), and Gal alpha 1-3Gal beta 1-4GLcNAc was ten times more efficient (30 muM). The modification from alpha to beta anomeric configuration of the nonreducing end resulted in a complete loss of activity, while substitutions at the reducing end induced only a partial loss of activity. These observations suggest that natural anti-alphaGal antibodies recognize the epitope from its nonreducing end, but that substitutions at the reducing terminus can modify the antibody-binding capacity. Modified tri- and tetrasaccharides are better inhibitors than the disaccharide but not as good as Gal alpha 1-3Gal beta 1-4GlcNAc. The reducing terminus therefore contributes some energy to the reaction, indicating that certain oligosaccharides will be of more potential clinical use than others.

Animals↗
PubMed1996

A comparison of transplant patient and social worker attitudes in regard to transplant patient psychosocial selection criteria, role expectations and communication style.

Though much is known about organ transplant (TX) patient and family psychosocial needs, there is virtually no information about the nature of the interaction that exists between TX social workers and patients. A comparison of TX patient-social worker attitudes and beliefs found (i) patients supported a more egalitarian "consumer-centered" approach to health care, but were reluctant to assume the accompanying responsibility, and (ii) social workers were more "traditional" in their approach, which focused primarily on assessment and social support. Results argue for a more comprehensive clinical approach by social workers to deal with problems of patient compliance, substance abuse, and psychological needs in a TX service where emphasis is placed on results rather than subjective process measures.

Adult↗