Experimental studies on splenic autotransplantation in rats

To determine if splenic implants in the body regain vascularization and grow, and to determine the effects of any interaction between implant and remnant on growth of these spleen fragments, we conducted experiments on rats. 1) Spleen fragments were implanted in the omentum (20 cases), in the subcutaneous space (20 cases), or in the liver (10 cases), and the weight of splenic portions and its histological findings were observed 12 and 24 weeks after operation. The best splenic growth was observed in the group of implant in the omentum. 2) Total, 4/5, 2/3, 1/3 and 1/5 spleen were implanted in the omentum and the weight of implants were measured 6 weeks after the operation. The rate of growth of implanted spleen was the highest in the group of 1/5 and was the lowest in the group of whole spleen. 3) Two groups of rats underwent 1/3 splenectomy, and the 1/3 spleen portions was implanted in the omentum. One group had the remaining 2/3 spleen removed, the other group had the remaining 2/3 spleen left in place. In group at 6, 12 and 24 weeks postoperatively the splenic portions was weighed. The implants regenerate with time in rats of both groups. The rate of weight-gain was, however, slow in the group with 2/3 spleen and there was no regeneration on the remaining 2/3 spleen.     

Patterns of bacterial translocation in experimental biliary obstruction

INTRODUCTION: Biliary obstruction is associated with impaired intestinal barrier function and translocation of enteric bacteria to the systemic circulation. Traditional live culture techniques may overlook translocation of dead bacterial fragments that stimulate the inflammatory response. The aim of this study was to estimate the extent and pattern of bacterial translocation in experimental biliary obstruction. MATERIALS AND METHODS: Thirty 9-week-old male Wistar rats were randomized to undergo bile duct ligation (BDL, n = 20) or sham operation (n = 10). Seven days after operation, each animal received 1 ml of (111)indium-oxyquinolone-labeled Escherichia coli p.o. Samples of liver, spleen, mesenteric lymph nodes, and lung were harvested 4 h later and analyzed for live bacteria and (111)indium activity. RESULTS: There was significantly more live bacterial translocation detected in BDL animals than in sham-operated animals (P = 0.00008, chi(2)). Labeled bacterial fragments were detected in all locations sampled in all animals. Sham-operated animals had significantly more labeled bacterial fragments detected in the liver (P = 0.0001) and the spleen (P = 0.03) than the BDL animals. The mean total bacterial survival in the BDL group was 30 +/- 13% and 0% in the sham operated group. CONCLUSION: These results demonstrate that non-viable bacterial fragments are present in sterile extra-intestinal sites in normal animals and that translocation of live bacteria is markedly increased in experimental biliary obstruction. These results also suggest that failure of bacterial killing is an important factor facilitating bacterial translocation in the presence of established biliary obstruction.     

Inhibition of the graft-versus-host reaction. III. Altered in vivo distribution of spleen cells pretreated with Fab fragments of antithymocyte globulin.

51Cr-labeled parental strain spleen cells were pretreated in vitro with antithymocyte globulin (ATG) or Fab fragments of ATG before i.v. injection into F1 recipients. Recipients were killed at various intervals after injection and their organs were assayed for radioactivity in order to determine the in vivo distribution pattern of pretreated cells. 51Cr spleen cells pretreated with ATG were almost totally prevented from migrating to spleens, lymph nodes, bone marrow, Peyer's patches, lungs, and peripheral blood of recipients. Pretreatment of 51Cr spleen cells with noncytotoxic Fab of ATG also inhibited localization to these organs and tissues; however, the inhibition was not as complete as that of ATG-treated cells. Localization of Fab-treated 51Cr spleen cells to recipient nodes was inhibited to a greater extent than was localization to recipient spleens. There was no significant difference in the extent of inhibition of ATG-treated 51Cr spleen cells to recipient nodes and spleen. Organ counts from recipients killed at various intervals after injection of Fab-treated 51Cr spleen cells showed that Fab-treated cells do not recover their recirculating potential in vivo.     

Liver tissue fragments transplantation to the spleen

Sliced liver tissue fragments of strained Wistar-Lewis rat were transplanted to the spleen. Most of transplanted liver tissues showed hyaline degeneration and epithelial ducts, similar to bile ducts, were observed on the seventh day. The liver tissue could not be identified one month after transplantation. But the masses of hepatic cells, having no sinusoid, were observed in some cases 12 months after transplantation. Macroautoradiographic studies with 99mTc-diethyl-IDA, hepato-biliary agent, were performed. The yellowish white portions of the specimens on the seventh day, corresponded to the transplanted liver tissue, indicated the uptake of 99mTc-diethyl-IDA. This means the transplanted fragments were alive and had a role of detoxication. The density of the fragments were 20% to 50% of that of the host liver. The survival ratio in acute hepatic failure induced with carbon tetrachloride (CCl4) increased by the liver tissue fragments transplantation. The density of the transplanted fragments with hepatic injury by the CCl4 increased, compared with that of no injury.     

Induction of splenomegaly with stimulated leukocyte culture supernatants.

Cell-free medium from stimulated murine leukocyte cultures induced spleen enlargement in vitro. Splenomegaly was measured by [3H]leucine incorporation of spleen fragments in tissue culture. Stimulatory cell-free medium were induced in leukocyte cultures with allogeneic or phytohemagglutinin stimulation. Supernatant activity has lymphokine properties, i.e., cell-free soluble factor(s), generated during specific lymphocyte activation, but which are expressed without reference to H-2 specificity.     

Isolation and characterization of a variant duck orthoreovirus causing spleen necrosis in Peking ducks,China

Since December 2017, an infectious disease has caused economic hardship for duck farms and breeding ducks in many regions of China. This disease characterized by spleen necrosis and swelling, is due to a variant strain of duck orthoreovirus (DRV) (Duck/N‐DRV‐XT18/China/2018), which we isolated from the spleen of diseased ducks. After isolating the virus, we used next‐generation sequencing technology to determine the entire genomic of the virus. Our phylogenetic analysis of 10 genomic segments showed that the N‐DRV‐XT18 strain is closely related to orthoreovirus isolates derived from ducks and geese, with nucleotide sequence identities for 10 genomic fragments ranging between 49.8% and 99.3%. In contract, the nucleotide sequence of N‐DRV‐XT18 genomic fragments are only 38.6% to 78.8% similar to the chicken orthoreovirus isolate. Therefore, we determined that this pathogen, causing duck spleen necrosis, is a new variant of a duck orthoreovirus that is significantly different from any previously reported waterfowl‐derived othoreovirus.     

Analysis of survival of allogeneic fetal liver fragments in rats

The survival of allogeneic fetal liver fragments in the omentum was analyzed in rats. The lymphocyte subsets of the spleen and peripheral blood were also examined. When the fetal liver fragments were transplanted into the omentum, they survived for 2 wk, whereas adult liver fragments survived only 1 wk. In fetal liver fragments transplantation, the CD8 positive lymphocyte percentage in peripheral blood decreased significantly 3 wk after transplantation in comparison with that in adult liver fragment transplantation. The skin graft of the donor party showed a longer median survival time in rats receiving fetal liver fragment transplants than that in recipients of adult liver fragments. Although further study is needed, allogeneic fetal liver fragments survived longer in the omentum than reported elsewhere, and the decrease of CDS positive peripheral blood lymphocytes may have been the reason for this.     

基因修饰骨髓细胞移植后重建造血的实验观察

目的 探索利用基因标记技术观察造血重建的生物学特征。方法 利用脂质体介导将新霉素抵抗基因转导进入小鼠骨髓细胞。然后移植给受致死量照射的同种小鼠。观察受体小鼠造血的重建,并对造血重建后受体鼠的脾及骨髓细胞进行标志基因的检测。结果 移植小鼠健康存尖,并形成脾结节。而未经输注的对照鼠则很快死于骨髓衰竭。同时,移植骨的部分脾及骨髓细胞于Ｇ４１８体系中能够存活,经聚合酶链反应（ＰＣＲ）检测含有Ｎｅｏ＾Ｒ基因     

Immunobiology of xenogeneic cornea grafts in mouse eyes. II. Immunogenicity of xenogeneic cornea tissue grafts implanted in anterior chamber of mouse eyes

BACKGROUND: Xenogeneic corneal fragments (guinea pig) are highly resistant to immune rejection in the anterior chamber of mouse eyes. Because guinea pigs and mice are discordant (i.e., mouse serum normally contains guinea pig reactive xenoantibodies), we wished to determine the extent to which xenogeneic corneal fragments placed intraocularly in normal and specifically sensitized mice activated xenoreactive T and B cells. METHODS: Guinea pig corneas, deprived surgically of epithelium, were cut into fragments and inserted into the anterior chamber of eyes of BALB/c mice, adjacent to the central cornea of the recipient. Antibody (immunoglobulin [Ig]M, IgG) and delayed type hypersensitivity (DTH) immune responses of recipient mice to guinea pig xenoantigens were assessed. The fate of xenogeneic cornea implants was assessed in mice immunized systemically to guinea pig antigens. RESULTS: Guinea pig spleen cells and corneal fragments implanted s.c. induced within 2 weeks of immunization both DTH and IgG antibodies to guinea pig xenoantigens. By contrast, xenogeneic corneal fragments implanted in the anterior chamber of mouse eyes evoked no change in recipient humoral immune status and induced mild guinea pig-specific DTH only after 5 weeks. Presensitization of mice to guinea pig xenoantigens failed to increase the proportion of grafts that were regarded as rejected, but the onset of rejection in failed grafts occurred earlier than in unsensitized recipients. Active systemic immunization of mice bearing intracameral guinea pig corneal fragments failed to curtail the grafts' survival. Guinea pig corneal fragments implanted in the anterior chamber of normal mice failed to induce anterior chamber-associated immune deviation. CONCLUSIONS: Xenogeneic corneal fragments implanted in the anterior chamber of eyes of normal mice display strikingly reduced immunogenicity, and an inability to induce anterior chamber-associated immune deviation. These properties are discussed in terms of the vulnerability of guinea pig corneal tissue to immune rejection within the eye.     

Determination of intact splenic weight based on morcellated weight

Background: Comparisons of splenic size based on splenic weight are difficult after laparoscopic splenectomy, which results in a morcellated specimen. We report the results of a direct comparison between morcellated and intact splenic weights. Methods: Porcine spleens were harvested via a midline laparotomy, and an intact splenic weight was obtained, which served as the control. The spleen then was placed into an impermeable retrieval bag and returned to the peritoneal cavity. A separate 10-mm incision was made and the spleen mechanically morcellated with a uterine forceps. This design most faithfully recreates the morcellation process during laparoscopic splenectomy in humans. The aggregate weight of the fragments was compared with intact splenic weight. Results: Intact and morcellated weights were obtained from 58 porcine spleens. The mean intact splenic weight was 145 g, and the mean morcellated weight was 78 g. For a given morcellated weight achieved at laparoscopic splenectomy, an estimated intact weight can be determined by the following formula: intact weight (g) = morcellated weight (g) × 1.34 + 45. Conclusions: On the basis of our calculations, a normal spleen weighing 150 g would have a mean morcellated weight of 78 g, and splenomegaly (intact spleen weighing 250 g or more) would be defined by a morcellated weight exceeding 153 g. Presented at the Society of American Gastrointestinal Endoscopic Surgeons (SAGES) meeting, St. Louis, Missouri, USA, April 2001     

Method of treatment of combined injuries of the liver and spleen in children

Since 1980 operations for combined injuries of the liver and spleen have been made on 57 children aged from 5 through 16 years. Autografting of splenic tissue into the liver wound was performed in 17 (29.8%) patients using an original technique developed in experiments. The novelty of the suggested technique is that autografting of splenic tissue into the liver wound was followed by fixing the fragments with Pi-like stitches through the spleen transplant capsule. It ensures the impermeability of the liver wound, adequate hemostasis without applying artificial hemostatic materials and helps to avoid alloplastic materials for additional drainage of the subhepatic space, provides a direct physiological contact between the splenoid and liver tissue that is effective for prevention of hyposplenism following spleenectomy.     

Prevention of autoimmune diabetes with nonactivating anti-CD3 monoclonal antibody.

Autoreactive T cells mediate diabetes in animal models of insulin-dependent diabetes mellitus (IDDM) and are believed to cause the disease in humans. Therefore, immunotherapies directed against T cells are of particular interest for the treatment of IDDM. One candidate for such immunotherapy is anti-CD3 monoclonal antibodies (MoAbs), but clinical side effects are common with anti-CD3 treatment due to the ability of these MoAbs to activate T cells in vivo. However, F(ab')2 fragments of anti-CD3 are nonactivating and immunosuppressive. We evaluated the effects of whole anti-CD3 MoAb and F(ab')2 fragments in the setting of experimental autoimmune diabetes. Treatment with whole MoAb or F(ab')2 fragments significantly reduced the hyperglycemia induced with multiple low dosages of streptozocin (MDSDM; 232 +/- 23 mg/dl, P less than 0.01 and 235 +/- 16 mg/dl, P less than 0.01 vs. 325 +/- 25 mg/dl, respectively) in male CD1 mice. Both whole MoAb and F(ab')2 fragments suppressed the development of insulitis (P less than 0.001). Treatment with whole MoAb resulted in marked weight loss (10.4 +/- 1.5% of total body wt), and the mice appeared ill and listless, whereas, mice treated with F(ab')2 fragments gained weight (4.9 +/- 5.5% of total body wt) and appeared healthy. Treatment with whole MoAb caused activation of T cells in vivo as reflected by proliferation of freshly isolated spleen cells to recombinant interleukin-2. Depletion of T cells with whole MoAb was more pronounced than with F(ab')2 fragments, and T-cell receptor (TCR) reexpression on remaining cells occurred with F(ab')2 fragments within 48 h after F(ab')2 treatment.(ABSTRACT TRUNCATED AT 250 WORDS)     

Splenic autotransplantation: determination of the optimum amount required for maximum survival

Splenic salvage in cases of traumatic or iatrogenic injuries may require autotransplantation of splenic fragments when splenorrhaphy or partial splenectomy is not possible. There are no studies which address the issue concerning the optimal amount of spleen to be transplanted in order to yield maximal survival in a model of pneumococcal sepsis. This study uses a Sprague-Dawley rat model to attempt to clarify this issue. Animals were divided into seven groups: control, total splenectomy, 25, 40, 60, 80, and 100% omental pouch autotransplantation. These animals were challenged with intravenous Streptococcus pneumonia Type I after 24 weeks, and mortality and blood culture results were monitored. Transplants were recovered and weights were compared with the weights originally transplanted. Survival and blood culture results were seen to improve in a linear quantitative fashion as the amount of spleen autotransplanted increased up to 80%, after which no further improvement was seen. This data supports the autotransplantation of 80% of the spleen in the Sprague-Dawley rat as the optimum amount to achieve maximal survival in a model of pneumococcal sepsis.     

Laparoscopic splenectomy — technical aspects

Summary Since the recent development of endoscopic cholecystectomy various other digestive disorders have been treated endoscopically. Using the endo-GIA stapler the authors report a case of laparoscopic splenectomy. Five trocar sheaths were used. Once detached, the spleen was cut into fragments in a plastic bag intraabdominally, which allowed its removal. Splenectomy was performed for a girl who had an autoimmune thrombocytopenic purpura (ITP). No operative transfusion was required. The patient was discharged after an uncomplicated postoperative recovery. The cosmetic result is good.     

Immunological characteristics of purified pancreatic islet grafts

In a DBA/2 (H-2d) pancreatic islet-to-B6AF1 (H-2b/k.d) recipient combination, the graft survival of hand-picked islets was compared with that of "crude digested" islets that were prepared simply by collagenase digestion and Ficoll gradient separation and were contaminated with lymph nodes and vascular and ductal tissue. Islet allografts were transplanted into the renal subcapsular space of streptozotocin-induced diabetic recipients. No immunosuppression was used. All the crude digested islet allografts were acutely rejected between days 7 and 18 with a median survival time (MST) of 10.2 +/- 2.5 days. In contrast, 33% (3/9) of the purified islet allografts survived more than 100 days. Simultaneous transplantation of purified islets and contaminating tissue resulted in a shorter graft survival (MST of 15.6 +/- 3.7 days). When 5 X 10(7) donor strain spleen cells were injected i.v. at the time of transplantation, all purified islet grafts were acutely rejected within 9 days. In addition, the rejection time of the purified islet allografts was inversely correlated with the number of donor spleen cells injected. These results indicate that contaminating tissues such as lymph nodes, vascular tissue, and ductal fragments present in the crude digested islet allografts are a major stimulus for induction of an immune response resulting in acute rejection of islet allografts.     

Autotransplantation of pancreatic islets without separation of exocrine and endocrine tissue in totally pancreatectomized dogs.

The aims of this study were to determine whether diabetes could be ameliorated in dogs by autotransplantation of pancreatic fragments to the spleen and to determine the optimal time of collagenase digestion for pancreatic tissue dispersal. Forty-eight dogs were made diabetic by total pancreatectomy. Fifteen dogs not further treated survived 7.0+/-1.1 (SE) days with a mean plasma glucose of 401+/-5 (SE) mg/100 ml 2 days after pancreatectomy. The pancreases of 33 dogs were distended with Hanks' solution, minced, digested with collagenase (600 microns/ml of tissue), for 0 to 25 minutes, and autotransplanted to the splenic pulp. The incidence of permanent normoglycemia (fasting plasma glucose less than 150 mg/100 ml) and the K value of glucose tolerance tests (GTT) performed 2 and 10 weeks after transplant were determined in experimental groups divided according to the length of collagenase digestion. All five dogs receiving undigested tissue remained hyperglycemic. One of seven dogs receiving tissue digested for 10 minutes became normoglycemic. In contrast, seven of eight, seven of seven, and six of six dogs receiving tissue digested for 15, 20, and 25 minutes, respectively, became normoglycemic (followed for 6 months). K values at 2 weeks were 1.20+/-1.19 (SE)% 1.60+/-0.25 (SE)%, and 0.78+/-0.08 (SE)% in the normolgycemic dogs of the 15, 20, and 25 minute digestion groups, respectively. The K value of normal dogs was 3.30+/-0.27 (SE)%. The glucose tolerance curves of the 20 minute group at 2 and 10 weeks most nearly approximated the curves of normal dogs. K values improved in all recipient dogs. Diabetes recurred immediately and death occurred at a mean of 4.8+/-1.5 days in 12 recipient dogs following splenectomy. We conclude that pancreatic fragments can be successfully autotransplanted to the spleen without separation of endocrine and exocrine tissue and that 20 minutes is the optimal period of collagenase digestion for tissue preparation.     

A role for CD2 antibodies (BTI-322 and its humanized form) in the in vivo elimination of human T lymphocytes infiltrating an allogeneic human skin graft in SCID mice: an Fcgamma receptor-related mechanism involving co-injected human NK cells

BACKGROUND: Pilot clinical studies have shown that the rat anti-human-CD2 monoclonal antibody, LoCD2a/BTI-322, can efficiently prevent and treat acute kidney rejection. However, the in vivo mechanism by which it prevents allograft rejection has not been studied. BTI-322 and its humanized form have been shown to mediate in vitro antibody-dependent cell-mediated cytotoxicity (ADCC) against CD2 cells through the activation of monocytes or natural killer (NK) cells. METHODS: Human fetal skin samples were grafted into severe combined immunodeficient/nonobese diabetic mice. Five weeks later (day 0), the mice were injected with human allogeneic peripheral blood lymphocytes (PBL). Either on day 0 or on day 14, mice were treated with BTI-322, hu-BTI-322, or their F(ab')2 fragments. Peripheral blood mononuclear cells (PBMC) thoroughly devoid of NK cells were also assayed. RESULTS: After injection of PBL, the human skins became heavily infiltrated with activated human T lymphocytes, resulting in dermal microvascular injuries indicative of graft rejection. Early treatment with BTI-322 and hu-BTI-322 prevented all these events. These CD2 antibodies rapidly eliminated human T lymphocytes that had already infiltrated the grafts, with no evidence of recirculation toward the spleen. Their F(ab')2 fragments were, in contrast, ineffective. Elimination of NK cells from injected PBMC prevented the curative effect exerted by whole CD2 antibodies. It also abrogated their cytotoxicity potential against CD2 cells in ADCC assays. CONCLUSION: F(ab')2 fragments of the CD2 antibodies could not prevent allograft rejection, whereas whole immunoglobulin G could, and human NK cells were required for the curative effect exerted by these antibodies. The results are consistent with an FcgammaR-dependent ADCC mechanism mediated in vivo by human NK cells.     

Intra-abdominal splenosis following laparoscopic splenectomy causing recurrence in a child with chronic immune thrombocytopenic purpura

In this paper, we present the case of a 12-year-old boy with refractory, symptomatic immune thrombocytopenic purpura (ITP) who underwent a laparoscopic splenectomy (LS). During morcellation of the spleen the retrieval bag ruptured. Thirteen (13) months postoperatively, the patient developed further symptoms and was found to be thrombocytopenic. Tc-99m heat-damaged red blood cell scintigraphy showed an accumulation of heat-damaged red cells in the upper left quadrant, raising the possibility of missed accessory spleen. Laparoscopic exploration revealed widespread intra-abdominal splenosis, and a therapeutic omentectomy was carried out. Fourteen (14) months post-surgery, platelet counts improved and the patient remains well. Following an elective splenectomy, a relapse in ITP may be the result of missed accessory spleen or splenosis; in others, it may the result of ongoing platelet consumption in non-splenic, reticulo-endothelial tissue. During LS, consideration must therefore be given to the risk of not only leaving additional splenic tissue behind, but also to the possibility of accidental autotransplantation, such as that from laparoscopic bag rupture. The risk of rupture can be minimized by using blunt instruments and stronger bag materials. If a rupture does occur, immediate suction and a thorough search for splenic fragments must be undertaken. Further development is needed into new techniques for organ retrieval and stronger bag materials.     

Ballistic trauma to the abdomen: shell fragments versus bullets

Two-hundred ninety-nine patients who sustained penetrating ballistic trauma to the abdomen were divided into two groups: Group A consisted of 133 patients with shell fragment injuries from mortar artillery and Group B of 166 patients with bullet injuries from rifles and automatic or semiautomatic weapons. Both groups were analyzed retrospectively in order to compare the extent of injury and outcome. In Group A, the findings at laparotomy were negative in 15 of 133 patients (10%) compared with 9 of 166 patients (5%) in Group B (p less than 0.05). The most commonly injured abdominal organs in Group A were the colon (42%), liver (22%), small bowel (20%), stomach (14%), diaphragm (11%), spleen (10%), major vessels (40%) [corrected], and kidney (9%). The abdominal organs commonly injured in Group B were the colon (50%), small bowel (41%), liver (33%), major vessels (20%), diaphragm (17%), stomach (15%), spleen (15%), and kidney (15%). Associated extra-abdominal injuries were present in 26% of Group A patients and in 21% of Group B patients (p greater than 0.05) [corrected]. Major postoperative complications occurred in 7.5% and 8.4% of the patients in Group A and Group B, respectively (p less than 0.05). Perioperative mortality was 2.3% in Group A versus 7.2% in Group B (p less than 0.01). Our data suggest that high energy bullets to the abdomen cause higher tissue penetration and a greater blast effect than shell fragments.     

Idarubicin-145-2C11-F(ab')2 promotes peripheral tolerance and reduces chronic vascular disease in mouse cardiac allografts

In order to reduce the toxic effects of the T cell activating anti-CD3 monoclonal antibody, 145-2C11, F(ab')2 fragments were prepared by pepsin digestion. These fragments were then used as non-immunosuppressive carriers for the cytotoxic drug idarubicin (IDA), to reduce toxicity of both the monodonal antibodies (mAb) and the drug and to increase the specificity of drug delivery. The IDA-145-2C11 F(ab')2 immunoconjugate was tested for specificity by fluorometry. 145-2C11 intact antibody, 145-2C11 F(ab')2 and IDA conjugates of the antibody and F(ab')2 were used to treat CBA recipients of BALB/c vascularized cardiac allografts. Mice with hearts surviving >100 days were challenged with donor and third party (C57BL/6) skin grafts. Although both antibody and F(ab')2 blocked the binding of 145-2C11-FITC to CBA spleen cells, only the intact antibody caused sustained depletion of CD3 cells in vivo. 145-2C11 F(ab')2 blocked cell surface CD3 within 30 min, but was cleared in 24 h without depletion of CD3 cells from the spleen. In BALB/c to CBA cardiac allografts (rejected in 12-17 days), IDA-145-2C11 F(ab')2 (0.2 mg/20 g mouse i.p. at the time of transplantation) induced >100 days' allograft survival and specific tolerance, in contrast to the equivalent dose of 145-2C11 F(ab')2 (mean survival 25 days). Hearts from IDA-145-2C11 F(ab')2-treated mice at >100 days showed decreased cellular infiltration and less chronic vascular disease than long-surviving hearts from mice treated with an alternative antibody, KT3. Thus, F(ab')2 prepared from 145-2C11 provided a suitable CD3-specific, nonimmunosuppressive carrier for IDA. This immunoconjugate was more effective against both acute and chronic rejection than other conjugates or whole antibody. IDA-145-2C11 F(ab')2 is an effective, nontoxic tolerogen in the mouse cardiac allograft model.