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Biomedical subjects

H T Lau

Publications and source records attributed to H T Lau.

18 recordsLinked to original sources
PubMed1996

Prevention of islet allograft rejection with engineered myoblasts expressing FasL in mice.

Allogeneic transplantation of islets of Langerhans was facilitated by the cotransplantation of syngeneic myoblasts genetically engineered to express the Fas ligand (FasL). Composite grafting of allogeneic islets with syngeneic myoblasts expressing FasL protected the islet graft from immune rejection and maintained normoglycemia for more than 80 days in mice with streptozotocin-induced diabetes. Graft survival was not prolonged with composite grafts of unmodified myoblasts or Fas-expressing myoblasts. Islet allografts transplanted separately from FasL-expressing myoblasts into the contralateral kidney were rejected, as were similarly transplanted third-party thyroid allografts. Thus, the FasL signal provided site- and immune-specific protection of islet allografts.

Animals↗
PubMed1996

Epstein-Barr virus-associated hepatic smooth muscle neoplasm in a cardiac transplant recipient.

Host immunosuppression is increasingly recognized as a significant risk factor for the development of a primary neoplasm. Chronic immunosuppressive therapy, as used in organ transplantation, may perturb the immunosurveillance ability of the host, making the patient more susceptible to virus-associated malignancies. We have taken care of a care of a child who received an orthotopic heart transplant and who then developed both a generalized lymphoproliferative disorder and a leiomyoma of the liver a year later. Epstein-Barr virus DNA was detected in a lymph node initially and the hepatic tumor cells subsequently. The former responded to a reduction in the immunosuppressive medications and the latter responded to surgical resection. This is the first report of a hepatic smooth cell neoplasm occurring following cardiac transplant and the development of two sequential Epstein-Barr virus-associated disorders in an immunosuppressed patient.

Child↗
PubMed1996

Lethal airbag injury in an infant.

Airbag injuries to automobile passengers are increasing in frequency, but the majority of reported injuries have been relatively minor and have occurred in adults. The National Highway Traffic Safety Administration (NHTSA) has identified a potentially lethal injury mechanism that occurs when safety seats are placed rear-facing on the passenger side of a vehicle equipped with a passenger side airbag. We report the first case of infant fatality resulting from passenger side airbag deployment that validates this mechanism.

Accidents, Traffic↗
PubMed1995

Immunomodulation of pancreatic islet allografts in mice with CTLA4Ig secreting muscle cells.

In an effort to create a model of in vivo production of immunosuppressants, we have transfected C2C12 muscle cells (H-2k) with the cDNA for CTLA4Ig, a fusion protein that prevents the activation of T cells by blocking the costimulatory signal transduced by the T cell receptors CD28 and CTLA4. CTLA4Ig-secreting clones were cotransplanted with islets as composite grafts in the renal subcapsular space of diabetic mice. When the myoblasts were syngeneic to C3H/HeJ hosts (H-2k), there was a significant prolongation of survival of allogeneic C57Bl/6J (H-2b) islets from a mean 11.0 days to 31.7 days. When the graft was completely allogeneic (H-2k myoblasts and islets into H-2b recipients), there was no benefit in survival. A transient blockade of LFA-1 with the mAb M17 was synergistic in this combination: 8 out of 12 C57Bl/6J recipients achieved long-term acceptance. Systemic CTLA4Ig levels were detected up to 60 days after transplantation. In conclusion, we have shown that C2C12 muscle cells can be genetically engineered to secrete functional CTLA4Ig and that they can be used as a gene reservoir for the continuous in vivo production of CTLA4Ig to modulate the survival of islet cell allografts.

Abatacept↗
PubMed1992

Prolongation of allograft and xenograft survival in mice by anti-CD2 monoclonal antibodies.

Anti-CD2 monoclonal antibodies (mAb) were used to influence graft survival in two transplantation models. Xenogeneic rat islets were transplanted intraportally into mice. Anti-CD2 mAb prolonged xenograft survival and was synergistic with UVB irradiation in prolonging survival. Anti-CD2 mAb was also more potent than an anti-CD4 mAb in this model. Allogeneic cardiac grafts were transplanted across an entire H-2 difference and anti-CD2 mAb prolonged allograft survival in a dose-dependent fashion. Kinetic experiments revealed that anti-CD2 mAb was most potent when administered at the time of allografting. A delay in administration of mAb markedly reduced its immunosuppressive effects. Furthermore, additional doses of mAb given after the initial doses provided no increased immunosuppression and anti-CD2 mAbs did not delay rejection of second-set allografts. These findings support the notion that anti-CD2 mAbs interfere with afferent immunity and that CD2 is most important during the initial steps of an immune response. Investigation of the effect of anti-CD2 mAb on cellular immune functions demonstrated, in agreement with previous results, that it caused antigenic down-modulation of CD2 with relative sparing of CD3, CD4, and CD8 cell surface expression. Concomitantly the MLR, CTL, and NK responses were suppressed.

Animals↗
PubMed1990

A trilaminar skin coverage technique for treatment of severe degloving injuries of the extremities and torso.

A 60 percent degloving injury involving the torso and lower extremities of an 8-year-old boy is described. Successful management employed the use of a new trilaminar skin coverage technique. With the avulsed flap still attached to its bed, a 0.14-inch split-thickness graft of epithelium and superficial dermis is raised with a power-driven dermatome. From the same harvest site, one level deeper, a second layer consisting of split-thickness dermis (0.14 inch) is taken. Both the first and second layers are meshed and expanded. The remaining degloved flap is excised and, on a sterile bench, defatted to produce a third layer of deep dermis. In our case, this third layer was ultimately lost, but it functioned well as a temporary biologic dressing. Depending on donor-site morbidity, other potential applications of this method (i.e., major burn injuries) may be feasible.

Body Surface Area↗
PubMed1988

Effect of ultraviolet-B-irradiated donor-specific blood transfusions and peritransplant immunosuppression with cyclosporine on rat cardiac allograft survival.

We have previously demonstrated that pretreatment of ACI recipients with ultraviolet-irradiated donor-specific blood transfusion (UV-DST) leads to permanent cardiac allograft survival without further host immunosuppression (ACI rats are weak responders to Lewis lymphocytes in mixed-lymphocyte reaction). This study examines the effect of UV-DST and the timing of transfusions on ACI cardiac allograft survival in Lewis recipients with and without the addition of peritransplant cyclosporine (CsA) (20 mg/kg i.m.) given on days 0, +1, and +2 in relation to the time of transplantation. The mean survival time (MST) of ACI cardiac allografts in Lewis recipients was significantly increased to 33.6 +/- 5.7 days (P less than 0.001) by CsA treatment alone as compared to 6.5 +/- 0.5 days survival in control. When DST was given on day -3 combined with CsA, graft survival was increased to 42.0 +/- 9.3 days (P less than 0.01), as compared to 5.8 +/- 1.3 days when DST alone was used. When DST was irradiated with ultraviolet B (UV-DST) and administered on day -3 combined with peritransplant CsA, the MST was increased to 68.83 +/- 16.1 days as compared to an MST of 10.0 +/- 1.0 days in controls treated with UV-DST alone. When UV-DST was given on day -7 and combined with peritransplant CsA immunosuppression, the results were similar. However, when UV-DST was peritransplant CsA course, 4 of 6 recipients maintained their ACI heart allografts indefinitely (greater than 300 days) in contrast to the effect of UV-DST alone (MST of 13.5 days). Third-party (W/F) UV-irradiated blood transfusions were ineffective in prolonging ACI cardiac allografts in Lewis rats, regardless of whether the transfusions were given alone or in combination with peritransplant immunosuppression with CsA. In conclusion, these results demonstrate that UV-DST combined with a brief peritransplant immunosuppression with CsA induces prolonged heart allograft survival in a histoincompatible, strong responder host, and that such effect is donor specific. The use of UV-DST combined with peritransplant CsA immunosuppression offers a promising approach to achieving organ transplant unresponsiveness, and decreased sensitization to the donor blood elements, which eventually may have important clinical implications.

Animals↗
PubMed1983

Decreased pulmonary alveolar macrophage bactericidal activity in splenectomized rats.

The organism most frequently encountered in postsplenectomy sepsis is Streptococcus pneumoniae, which is thought to invade via the upper respiratory tract. This study assesses the phagocytic and bactericidal activity of pulmonary alveolar macrophages (PAM) in normal, splenectomized, and one-third splenectomized autotransplanted rats at 8 weeks of age, 7 weeks post surgery. The PAMs from both the splenectomized and control rats all expressed the same ability to phagocytose latex beads and Fc-receptor-mediated phagocytosis of SRBC. In the bactericidal assay, bacterial growth, after 1 hr without macrophages, was 31 X 10(3) colony-forming units (CFU). In the presence of PAMs from splenectomized rats, the colony count was 22 X 10(3) (P less than 0.2). Bactericidal activity was highly evident when PAMs from control and autotransplanted rats were assayed, with CFU of 11.3 X 10(3) and 14.6 X 10(3), respectively (P less than 0.001, P less than 0.002, respectively). It is concluded that antibody-dependent and independent phagocytic activity of PAMs is unimpaired in splenectomized rats as compared to controls. The defect in rats splenectomized at 1 week of age resides in poor pneumococcal bactericidal activity of PAMs and is almost completely corrected by ip autotransplantation of one-third of the spleen.

Animals↗