PubMed Health⌕ Search

Biomedical subjects

L Makowka

Publications and source records attributed to L Makowka.

At least 73 records · Page 4Linked to original sources
PubMed1993

Pig aortic endothelial cell antigens recognized by human IgM natural antibodies.

Human-to-pig xenoantibodies may constitute a major obstacle to the successful use of pigs as xenograft donors for human transplantation. Our studies demonstrate that normal human serum contains antibodies, primarily IgM, that are cytotoxic for pig aortic endothelial cells (PAECs). These antibodies bind to several antigens isolated from PAECs, lymphocytes, platelets, red blood cells, and the kidney. Absorption of human serum with pig lymphocytes removes the cytotoxic activity to PAECs and some, but not all, of the IgM antibodies capable of binding in an ELISA assay to the PAECs. The cytotoxic antibodies are inactivated by 2-mercaptoethanol, suggesting that they are primarily IgM. Whole cell extracts of PAEC, lymphocytes, platelets, red blood cells, and kidney were prepared and analyzed by Western blots to establish the cellular distribution of the xenoantigens that react with human IgM in pooled human serum. Results showed that several of the most intensely stained bands migrated between 24 and 66 kDa. High molecular weight bands (> 100 kDa) were observed only in kidney, platelet, and PAEC preparations. Human IgM xeniantibodies also reacted strongly in Western blots to endothelial cell membranes proteins with molecular weights of 62, 48, 42, 36, 34, 28, and 26 kDa. Absorption of human serum with pig lymphocytes removes IgM binding to all bands except for a 34-kDa Treatment of the PAEC membrane proteins with proteinase K disrupts the binding of the human IgM antibodies. Similar treatment with glycosidase F) resulted in a decrease in molecular weight of the 28- and 26-kDa bands, suggesting that these xenoantigens are glycoproteins and that antibody binding to some xenoantigens may not require glycosylation.

Animals↗
PubMed1993

The synergism of brequinar sodium and cyclosporine used in combination to prevent cardiac allograft rejection in the rat.

Brequinar sodium (BQR) is a novel immunosuppressive drug that inhibits cell proliferation by virtue of its disruption of the de novo pyrimidine biosynthesis. The basis of the immunosuppressive activity of BQR is distinctively different from that of cyclosporine (CsA), and we have recently evaluated in vivo and in vitro the efficacy of the two drugs when used in combination. Subtherapeutic doses of BQR and CsA were tested for their ability to prolong heterotopic cardiac allograft survival in the MHC- and non-MHC-mismatched ACI-->LEW rat strain combination. The graft survival data derived from these experiments were analyzed using the median-effect analysis to establish the immunosuppressive interaction of both drugs. The administration of BQR 3 mg/kg three times weekly or CsA 2.5 mg/kg daily moderately prolonged cardiac allograft survival, with a mean survival of 10 +/- 0.5 and 16 +/- 5.3 days, respectively. The use of the two drugs in combination with the same dose schedule exerted a synergistic effect on graft survival, prolonging the graft function to a mean of 31 +/- 5.7 days. Sera from animals treated with the two drugs displayed, when compared with single treatment groups (BQR 3 mg/kg and CsA 2.5 mg/kg), significantly (P < 0.01) increased in vitro inhibition of lymphocyte proliferation following stimulation with PHA. Finally, a clear correlation between the mean survival time and BQR plasma levels of animals treated with BQR alone or in combination with CsA was seen. Those treatment groups with BQR levels below 2 micrograms/ml (1.5 and 3.0 mg/kg/3x/week) had a mean graft survival of less than 10 days). In contrast, recipients treated with a combination of low doses of BQR and CsA displayed higher drug plasma levels (> 2 micrograms/ml) and longer mean graft survival times. These observations suggest that BQR and CsA may be highly effective when used in combination to prevent organ allograft rejection for clinical transplantation.

Animals↗
PubMed1993

The prevention of accelerated cardiac allograft rejection in sensitized recipients after treatment with brequinar sodium.

Brequinar sodium (BQR) is a novel immunosuppressive agent that is highly effective in preventing B lymphocyte-mediated antibody production. We have examined the effects of BQR treatment in sensitized recipients on graft survival, donor-specific antibody responses (IgM and IgG), and the appearance of immunopathological lesions present in the grafts. LEW rat recipients were sensitized with single ACI skin graft on day 7 and received heterotopic ACI cardiac grafts on day 0. The recipients rejected the cardiac grafts in an accelerated fashion at day 2.5 post-transplantation, compared to day 7.0 in unsensitized recipients. The animals were treated with low (3 mg/kg/day) or high (12 mg/kg/3x weekly) doses of BQR during skin graft sensitization and/or after challenge with ACI heart allografts. All groups treated with BQR showed significant prolongation of graft survival in the sensitized recipients. The best survival was observed following high-dose BQR therapy during both sensitization and effector phases (median survival time = 40.0 days, P << 0.001). Daily treatment with BQR (3 mg/kg/day) prevented IgM (but not IgG) antibody responses. Treatment with higher doses of BQR (12 mg/kg/3x weekly) before and after skin graft sensitization was effective in preventing both IgM and IgG production. In general, BQR treatment resulted in effective suppression of anti-donor antibody responses, stable graft function, and a reduction in the severity of the acute vascular lesions in the graft. The effectiveness of BQR in preventing accelerated graft rejection when used at 12 mg/kg/3x weekly was comparable to that seen with treatment of sensitized animals with CsA at 15 mg/kg/day for 30 days. Daily treatment with cyclophosphamide at 5 or 15 mg/kg/day was ineffective for preventing graft rejection in sensitized recipients. These results indicated that BQR may provide an important addition to treatment protocols designed to prevent transplantation rejection in presensitized patients. BQR has the ability to significantly inhibit host cellular and humoral immune responses to the donor graft and this facet of the immunosuppressive activity of the drug may be responsible for preventing this aggressive form of rejection.

Animals↗
PubMed1993

The development of Brequinar as an immunosuppressive drug for transplantation.

The preclinical and clinical characterization of Brequinar sodium has demonstrated the potential for the use of this drug as a component of a polytherapeutic treatment strategy to prevent the rejection of organ grafts. Brequinar, along with several other new immunosuppressive drugs, including Mizorbine, 15-deoxyspergualin, and Mycophenolate mofetil, is an antimetabolite with immunosuppressive activity and toxic side effects that are distinctly different from those of CsA and the newly characterized FK 506. This combination of effective antiproliferative activity exhibited by these newer agents and the well-established effect of CsA on T-lymphocyte activation offers the potential for the development of immunosuppressive regimens that are significantly more effective with fewer side effects for the patient. The concept of synergistic interaction between these two classes of immunosuppressive agents has been tested experimentally and found to be extremely effective for both allograft and xenograft models of graft rejection (Cosenza et al. 1993, 1993a, Stepkowski & Kahan 1993). It remains to be established that a similar synergism will exist for clinical transplantation. The effectiveness of CsA as a primary immunosuppressive agent, however, assures the inclusion of CsA in any polytherapeutic approach to be tested in the near future. New clinical trials designed to prove efficacy for immunosuppressive agents, such as BQR, will use CsA or FK 506 as a primary component of the treatment protocol. The combination of immunosuppressive agents that will eventually be applied in wide clinical use is not clear. While some new immunosuppressive agents have been more extensively tested clinically, BQR exhibits a number of unique features that make this compound particularly attractive for inclusion in new immunosuppressive regimens. The drug is readily soluble in aqueous solutions and can be administered intravenously or orally with equal effectiveness. Brequinar exhibits a high level of bioavailability following oral administration and an extended half-life that permits less frequent administration. While the metabolic byproducts of BQR have not been clearly described, there is good evidence that the parent compound exhibits the majority, if not all, of the immunosuppressive activity. The ability to monitor the parent drug directly or measure the depletion of enzyme products that reflect the activity of the drug are important features of the drug that simplify its use in a clinical setting. Although BQR exhibits important adverse side effects at high doses, the effects of the drug are characteristic of antimetabolites and are therefore predictable, constant, and reversible.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1993

Immunosuppression in organ transplantation.

Recent advances in the development of immunosuppressive agents, including newer immunophylin drugs such as FK-506 and lymphocyte DNA synthesis inhibitors such as RS-61443, have allowed rapid progress to be achieved in the prevention and treatment of allograft rejection. Soon, these drugs will join cyclosporine and OKT3 as significant advancements in our battle against allograft loss and dysfunction caused by rejection. Newer developments in immunosuppressive therapy depend on our ability to understand how the immune system works in mediating allograft destructive events. Therefore it is critical that our basic understanding of immunologic mechanisms be incorporated into the development and use of current and future immunosuppressive agents.

Child↗
PubMed1993

Pediatric liver transplantation.

The excellent survival rates that have been achieved by pediatric liver transplantation today can be attributed to a multitude of factors. Refinements in immunosuppressive regimens, new immunosuppressive agents, improvements in surgical technique, and a better understanding of the unique issues that pertain to patient care have resulted in not only excellent survival rates, but also improvements in quality of life. The future promises even more progress in the directions of tolerance induction, expansion of the donor organ pool, and genetic manipulation allowing cellular transplantation for correction of inborn errors of metabolism.

Adolescent↗
PubMed1993

Prevention of vascularized allograft and xenograft rejection in rodents by brequinar sodium.

The data that has been obtained from preclinical studies in rodents demonstrate that BQR is an effective primary immunosuppressive agent with important advantages for use in transplantation immunotherapy. The drug is highly effective when used as a single agent to prevent the rejection of a variety of vascularized allografts and xenografts. BQR is easily administered orally, the drug displays a high level of bioavailability, and drug plasma levels and immunosuppressive activity can be directly measured. The adverse side effects seen with the drug are those normally associated with antiproliferative drugs and are predictable and easily reversed by treatment withdrawal. Most importantly, perhaps, is the broad range of synergistic activity when used in combination with new immunosuppressive drugs. We believe that the combination of these attributes separate BQR from many of the new drugs now under study. Some, for example, do not exhibit synergism (CsA and FK 506), others have may have problems with inadequate oral bioavailability (MPM and rapamycin), and some exhibit the potential for substantial toxicity (15-DSG, myzorbine). The data derived from the use of BQR in combination with other immunosuppressive drugs, such as the studies described above, are important. They provide direct evidence to support the concept that the next important advances in immunosuppressive therapy will involve the use of an effective multidrug approach to preventing organ graft rejection. Combination therapies with immunosuppressive drugs that exhibit different modes of action improve graft survival, widen therapeutic windows, and reduce the risk of toxic side effects. The experimental evidence that several of these combinations are potentially useful is solid, consistent, and exciting. It is our expectation from the rodent experiments described in this symposium that the treatment of allograft (and perhaps xenograft) rejection will consist of the use of CsA (or FK 506), BQR, and a third drug such as rapamycin or mycophenolate mofetil, the choice of which will be heavily influenced by the development of either analogues of these drugs or perhaps new compounds with improved bioavailability and effective monitoring techniques.

Animals↗