Rapamycin and CTLA4Ig synergize to induce stable mixed chimerism without the need for CD40 blockade.

The mixed chimerism approach achieves donor-specific tolerance in organ transplantation, but clinical use is inhibited by the toxicities of current bone marrow (BM) transplantation (BMT) protocols. Blocking the CD40:CD154 pathway with anti-CD154 monoclonal antibodies (mAbs) is exceptionally potent in inducing mixed chimerism, but these mAbs are clinically not available. Defining the roles of donor and recipient CD40 in a murine allogeneic BMT model, we show that CD4 or CD8 activation through an intact direct or CD4 T cell activation through the indirect pathway is sufficient to trigger BM rejection despite CTLA4Ig treatment. In the absence of CD4 T cells, CD8 T cell activation via the direct pathway, in contrast, leads to a state of split tolerance. Interruption of the CD40 signals in both the direct and indirect pathway of allorecognition or lack of recipient CD154 is required for the induction of chimerism and tolerance. We developed a novel BMT protocol that induces mixed chimerism and donor-specific tolerance to fully mismatched cardiac allografts relying on CD28 costimulation blockade and mTOR inhibition without targeting the CD40 pathway. Notably, MHC-mismatched/minor antigen-matched skin grafts survive indefinitely whereas fully mismatched grafts are rejected, suggesting that non-MHC antigens cause graft rejection and split tolerance.

Persistent molecular microchimerism induces long-term tolerance towards a clinically relevant respiratory allergen.

BACKGROUND: Development of antigen-specific preventive strategies is a challenging goal in IgE-mediated allergy. We have recently shown in proof-of-concept experiments that allergy can be successfully prevented by induction of durable tolerance via molecular chimerism. Transplantation of syngeneic hematopoietic stem cells genetically modified to express the clinically relevant grass pollen allergen Phl p 5 into myeloablated recipients led to high levels of chimerism (i.e. macrochimerism) and completely abrogated Phl p 5-specific immunity despite repeated immunizations with Phl p 5. OBJECTIVE: It was unclear, however, whether microchimerism (drastically lower levels of chimerism) would be sufficient as well which would allow development of minimally toxic tolerance protocols. METHODS: Bone marrow cells were transduced with recombinant viruses integrating Phl p 5 to be expressed in a membrane-anchored fashion. The syngeneic modified cells were transplanted into non-myeloablated recipients that were subsequently immunized repeatedly with Phl p 5 and Bet v 1 (control). Molecular chimerism was monitored using flow cytometry and PCR. T cell, B-cell and effector-cell tolerance were assessed by allergen-specific proliferation assays, isotype levels in sera and RBL assays. RESULTS: Here we demonstrate that transplantation of Phl p 5-expressing bone marrow cells into recipients having received non-myeloablative irradiation resulted in chimerism persisting for the length of follow-up. Chimerism levels, however, declined from transient macrochimerism levels to persistent levels of microchimerism (followed for 11 months). Notably, these chimerism levels were sufficient to induce B-cell tolerance as no Phl p 5-specific IgE and other high affinity isotypes were detectable in sera of chimeric mice. Furthermore, T-cell and effector-cell tolerance were achieved. CONCLUSIONS AND CLINICAL RELEVANCE: Low levels of persistent molecular chimerism are sufficient to induce long-term tolerance in IgE-mediated allergy. These results suggest that it will be possible to develop minimally toxic conditioning regimens sufficient for low level engraftment of genetically modified bone marrow.

[Reactive acalculous cholecystitis: a bland and asymptomatic course--incidence of a classical stress disease]. / Reaktive steinfreie Cholecystitis: blande und asymptomatische Verlaufsform--zur Dunkelziffer einer klassischen Stresserkrankung.

A systematic search for reactive acalculous cholecystitis (RAC) performed from 11/85 until 11/87 rendered an incidence of 9 in 1272 patients recovering from surgery and 1 in 930 patients treated conservatively for various diseases. 8 patients presented with typical but discrete clinical symptoms whereas 2 remained asymptomatic. Abdominal sonography proved to be the most useful diagnostic procedure. The ratio of classic fulminant disease to cases presenting with lesser severity was calculated to be 1:50. All patients in this series were managed nonoperatively in respect to RAC. The pathoanatomic and pathogenetic context is reviewed and the author's impression corroborated that relevant cases may frequently go by unnoticed by clinicians.

[Acute cholecystitis in cholelithiasis: importance of early surgery (a comparative study)]. / Akute Cholezystitis bei Cholezystolithiasis: zum Stellenwert der Frühoperation--Eine vergleichende Studie.

The results of early surgery (ES) for acute calculous cholecystitis obtained in 74 patients operated on between 3/78 and 12/87 were compared with relevant data obtained in 74 sex- and age-matched patients with a history of acute cholecystitis operated on for biliary colic or jaundice during the same period. Operative procedures, incidence of jaundice and common bile duct calculi, duration of operation, number of patients requiring blood transfusions, surgical and general complications and mortality showed no significant difference. Only operative blood loss was significantly higher in the ES group, but this was of no practical relevance. ES precludes the sequelae of emergency surgery in the delayed surgery group not infrequently necessary for failure of conservative treatment of acute cholecystitis, which necessarily precedes planned delayed surgery, and thus renders a significant reduction of over-all risk. This forms the rationale for ES as treatment concept.