Removal of sulfamethizole from aqueous solution using advanced oxidation processes: effects of pH and salinity.

This study investigates the removal of sulfamethizole (SFZ) in ozone (O3), O3/Na2S2O8 (sodium persulfate), UV/Na2S2O8, UV/O3, and UV/O3/Na2S2O8 systems. The effects of pH and salinity on SFZ mineralization were evaluated. The mineralization of SFZ followed pseudo-first-order kinetics. At pH 5, the rate constants of SFZ mineralization in O3, O3/Na2S2O8, UV/Na2S2O8, UV/O3, and UV/O3/Na2S2O8 systems were 0.576, 0.924, 0.702, 1.26, and 5.21 h-1, respectively. The SFZ mineralization rate followed the order pH 5 > pH 7 > pH 9 in all tested advanced oxidation processes. Salinity increased the rate of SFZ mineralization in O3 and O3/Na2S2O8 systems and decelerated it in UV/Na2S2O8, UV/O3, and UV/O3/Na2S2O8 systems. UV/O3/Na2S2O8 was the best system for mineralizing SFZ, and sulfate radicals were the predominant species in UV/O3/Na2S2O8.

Review paper: Implications of the "cancer stem cell" hypothesis on murine models of colon cancer and colitis-associated cancer.

The use of murine models to investigate human diseases has been an invaluable tool. In the areas of inflammation and oncogenesis, such models have provided unique insights into pathogenesis and mechanisms to evaluate potential therapy. As such, one facet of these disease processes links inflammation and cancer. Inflammation is associated with at least 15% of the world's malignancies. One example of this relationship is documented in the association between colitis and colorectal cancer. To date, the precise molecular events linking inflammation and cancer remain unclear. A new paradigm that may bridge these processes includes the cancer stem cell hypothesis. In this review, murine models of colitis, colon cancer, and colitis-associated cancer are discussed in reference to the potential of this paradigm to clarify the relationship of these devastating diseases.

CDX2 does not suppress tumorigenicity in the human gastric cancer cell line MKN45.

CDX2 is a Drosophila caudal-related homeobox transcription factor that is expressed specifically in the intestine. In mice, ectopic expression of CDX2 in the gastric mucosa gives rise to intestinal metaplasia and in one model, gastric carcinoma. In humans, increased CDX2 expression is associated with gastric intestinal metaplasia and tubular adenocarcinomas. These patterns of expression have shown that CDX2 is important for the initiation of intestinal metaplasia in the gastric mucosa, but the role of CDX2 in established gastric cancer remains unclear. We sought to determine whether CDX2 contributes to tumorigenic potential in established gastric cancer. The CDX2 gene in MKN45 gastric carcinoma cells was disrupted using targeted homologous recombination. The resulting CDX2-/- cells are essentially identical to their parental cells, with the exception of CDX2 ablation. We found no significant differences in the proliferation of CDX2-/- cells compared to CDX2+/+ cells, in vitro or in vivo. Molecular analyses show that loss of CDX2 predominantly altered the expression of genes involved in intestinal glandular differentiation and adhesion. However, there were no microscopic differences in tumor differentiation. We conclude that disruption of CDX2 in MKN45 cells does not significantly affect their tumorigenic potential.

Surgical implications of colonoscopy.

Colonoscopy, although increasingly used as a screening tool, has many surgical applications. As a tool for the abdominal surgeon, colonoscopy may be used not only to diagnose neoplasia, but also hemorrhage, and inflammatory and obstructive disorders. Therapeutically, endoscopic polypectomy has impacted the incidence of colorectal cancer, and further visualization techniques have augmented the ability of the endoscopist to discriminate between benign and neoplastic lesions. Colonoscopy remains a necessary implement to facilitate the diagnosis and therapy of those patients with disorders of the colon and rectum.

The percentage of CD31+ T cells decreases after open but not laparoscopic surgery.

BACKGROUND: Efficient killing of tumor cells depends on T cells that migrate from the circulation to the peripheral tissues; these cells express CD31. This study was undertaken to determine the impact of open (OS) and laparoscopic (LS) colorectal surgery on the percentage of circulating CD3+CD31+ cells. METHODS: Peripheral blood was collected from 27 OS and 24 LS colon cancer patients preoperatively (preOP) and on postoperative days 1 (POD1) and 3 (POD3). CD31+ T cells were assessed by flow cytometry using monoclonal antibodies. RESULTS: In the OS group, the percentage of CD3+CD31+ cells was significantly lower in POD1 and POD3 samples compared to the preOP results. LS surgery did not result in a significant change in the percentage of these T cells. A significant correlation was found between the decrease in the percentage of CD3+CD31+ cells and the length of incision in OS patients. CONCLUSIONS: The percentage of CD3+CD31+ cells decreases following OS but not LS and may be related to incision length. This may compromise T cell function in the peripheral tissues in the postoperative period.

Colonoscopy in mice.

INTRODUCTION: Current investigational models of murine colitis and colon cancer necessitate sacrifice of animals in order to obtain colonic tissue. The purpose of this study was to develop a safe method of murine colonoscopy that would allow serial evaluation and mucosal biopsies of the same animal. METHODS: Nine mice (two C3H, two C57/BL6, and five IL-10 deficient) were studied a total of four times each over 4 weeks. Three mice [APC (Min +/-)] were examined three times each. Mice were gavaged with 1 cc of a polyethylene glycol solution on the day prior to colonoscopy. Solid chow was withheld and the mice were maintained on Pedialyte. Mice were anesthetized with ketamine and xylazine. A flexible pediatric cystoscope (2.1-mm diameter) with a single biopsy channel was introduced per anum, and the colon was gently insufflated with air to a mean pressure of less than 5 mmHg. Saline irrigation was used when necessary. A single biopsy was obtained from the rectosigmoid colon during each examination. RESULTS: A total of 46 examinations were carried out. One mouse died after being anesthesized for the fourth examination, and two mice [one IL-10 knockout and one APC (Min+/-)] died one day after the 3rd examination. No other complications were noted. The average length of insertion was 3 cm. Transillumination allowed for localization of the endoscope tip. Biopsies, although quite small, were sufficient for pathologic evaluation and diagnosis. CONCLUSIONS: Murine colonoscopy is a safe and feasible technique. It permits consecutive visual and histopathological examinations, and it allows the investigator to monitor the response of the murine colon to experimental interventions.

Increased incidence of colorectal adenomas in follow-up evaluation of patients with newly diagnosed hyperplastic polyps.

BACKGROUND: Although adenomatous polyps have been established clearly as precursor lesions for most cases of colorectal cancer, the role, if any, of hyperplastic polyps remains uncertain. The aim of the current study was to determine whether a patient with an index finding of hyperplastic polyp on colonoscopy is at increased risk for adenomatous polyps. METHODS: We conducted a retrospective cohort study using the records of a single surgeon's colonoscopic experience over a 20-year period (June 1973 to December 1994). Patients found to have hyperplastic lesions on index colonoscopy were compared with those who had "clean" index colonoscopies. The two groups were compared for the subsequent diagnosis of adenomatous polyps on follow-up colonoscopies. Those with cancer or adenomas at index colonoscopy or in their history were excluded. We used Cox proportional hazard modeling with subsequent adenoma or cancer diagnosis at follow-up colonoscopy as the outcome, controlling for age and gender. RESULTS: We identified 42 patients for whom hyperplastic polyps were the only colorectal neoplasms found on the index examination, in contrast to 362 control patients who had a "clean" index examination. In this cohort study, patients found to have only hyperplastic polyps on initial examination had a rate of subsequent adenoma diagnoses (42%) twice that of patients with a clean initial colonoscopy (21%). Mean follow-up time was 4.3 years. The relative rate ratio was 2.0 (95% confidence interval, 1.2-3.4). CONCLUSIONS: This study suggests that patients found to have hyperplastic polyps on initial colonoscopic examination may have twice the risk of adenomas on follow-up colonoscopy, as compared with those who have clean initial examinations. If this finding is borne out in larger prospective studies, surveillance strategies may need to be modified accordingly.

Hybrid laparoscopic flexure takedown and open procedure for rectal resection is associated with significantly shorter length of stay than equivalent open resection.

PURPOSE: Laparoscopic-assisted, sphincter-saving resection (largest incision < 7 cm) of the middle and distal rectum is technically very difficult and, with regard to cancers, has not been demonstrated to be oncologically safe. The hypothesis of this retrospective study is that a hybrid operation that combines laparoscopic and open methods would be associated with short-term outcome benefits compared with open surgery results for patients undergoing sphincter-saving proctectomy. METHODS: A total of 31 hybrid and 25 fully open rectal resection patients were compared in this retrospective review. All patients had splenic flexure takedown and rectal anastomosis. The hybrid approach consisted of laparoscopic splenic flexure takedown (with or without partial rectal mobilization and devascularization) followed by completion of the procedure via infraumbilical midline laparotomy. The indication was neoplasm in 87 percent of hybrid patients and in 68 percent of open patients. The majority of tumors were located between 4 and 10 cm from the dentate line. RESULTS: Fifty-eight percent of hybrid and 68 percent of open patients had low anterior or coloanal resections, and 48 percent of hybrid and 64 percent of open patients underwent temporary diversion via ileostomy. The mean hybrid midline incision length was 11 cm compared with 24 cm for open patients (P < 0.0001). The neoplastic specimens were similar with regard to margins and lymph node harvest. Similar complication rates were noted in both groups. Nonsignificant benefits for hybrid patients (0.9-1.2 days) were seen with regard to length of time until toleration of liquid or solid diet and first flatus. Hybrid patients experienced their first bowel movements 4.1 days vs. 5.7 days for the open group (P = 0.03). Mean length of stay was significantly shorter for hybrid patients (6.1. days) than for open patients (11.1 days; P = 0.0006). CONCLUSION: This preliminary retrospective study suggests that a combined hybrid laparoscopic and open approach to sphincter-saving proctectomy permits a similar resection as open methods and may be associated with a length-of-stay benefit and more rapid return of bowel function. Prospective studies will be needed before any firm conclusions can be drawn.

Increased platelet-derived growth factor (PDGF) release after laparotomy stimulates systemic tumor growth in mice.

BACKGROUND: Our laboratory has demonstrated that tumors grow larger and are more easily established following laparotomy than after carbon dioxide (CO2) pneumoperitoneum or anesthesia alone. We have also shown that tumor cells incubated with serum from laparotomized mice proliferated significantly faster in vitro than those incubated with plasma from mice that underwent laparoscopy or anesthesia alone. We hypothesized that differing levels of a plasma-soluble growth factor(s) postoperatively causes tumors to proliferate faster after laparotomy. This study's purpose was to isolate and characterize the plasma growth factor(s) responsible for the increased growth of systemic tumors after laparotomy. METHODS: Female Balb/C mice (n = 100) were randomized to two groups: anesthesia control (AC) or midline sham laparotomy (4 cm) (Open). Plasma was collected on Postoperative day 4. For the tumor proliferation assay, C-26 colon cancer cells were incubated in media with either 10% AC or Open "raw" plasma (not passed through column), or AC or Open plasma that had been passed through the column. For elution of heparin-binding proteins, plasma from each group was passed through a heparin-sepharose column. Elution of bound proteins was accomplished with a 0.1-2 M NaCl gradient. Each fraction was examined for protein content. For the anti-platelet-derived growth factor (PDGF) neutralizing antibody study, C-26 cells were incubated with one of four plasma preparations: AC or Open plasma alone, or AC or Open plasma incubated with anti-PDGF antibody. For both studies, tumor proliferation was determined after 2 days with an MTS/PMS assay. Results from each group were compared and differences determined using analysis of variance (ANOVA) and Tukey-Kramer tests. RESULTS: On heparin chromatography, a single elution peak consistent with PDGF was present in both AC and Open plasma and was 1.5 times greater in the Open plasma. The first tumor proliferation assay showed that tumor cells incubated with Open plasma proliferated 2.5 times faster than those with AC plasma (p < 0.0001). Passage of AC plasma through the column did not alter its mitogenic activity, but Open plasma thus treated demonstrated significantly decreased mitogenic activity. The second tumor proliferation assay showed that anti-PDGF antibody had no effect on the mitogenic activity of the AC plasma but decreased the mitogenic activity of the Open plasma to the AC plasma level. CONCLUSIONS: Laparotomy is associated with higher levels of a heparin-binding plasma factor, consistent with PDGF. The enhanced mitogenic activity of the OP plasma was neutralized with anti-PDGF antibody. Increased plasma levels of PDGF after laparotomy may be responsible for accelerated tumor growth following laparotomy in mice.

A serum-soluble factor(s) stimulates tumor growth following laparotomy in a murine model.

BACKGROUND: Our laboratory and others have previously demonstrated that tumors grow larger and are more easily established following laparotomy than after CO(2) pneumoperitoneum. The etiology of increased tumor growth after surgery is unknown. We hypothesized that, following laparotomy, a serum soluble factor(s) is generated that causes tumors to proliferate more rapidly. The purpose of the current study was to determine if in vitro tumor cells proliferate faster when incubated with serum from laparotomized mice than cells incubated with sera from mice who have undergone CO(2) pneumoperitoneum or anesthesia alone. METHODS: In the first experiment, female Balb/C mice (n = 84) were randomly divided into the following three groups: (a) control (AC), (b) CO(2) insufflation (INS), and (c) laparotomy (OPEN). The AC mice underwent no procedure. The INS group underwent CO(2) pneumoperitoneum at 4-6 mmHg for 20 min. The OPEN group had a midline incision from xiphoid to pubis. The serum of seven mice from each group were collected on postoperative days (POD) 1, 2, 4, and 7 via a cardiac puncture. The sera at each time point for each group were pooled. Twenty thousand C-26 colon cancer cells were incubated separately in growth media containing 10% mouse serum from each group (seven determinations/group) at each time point. In the second experiment, female Balb/C (n = 30) mice were divided into AC and OPEN groups. On POD4, sera were collected and pooled. Three separate studies were performed for the second experiment. In the first study, tumor cells were incubated with 10% AC sera or varying concentrations of OPEN mice sera (4-10%). In the second study, aliquots of sera from the OPEN group mice were then heated at 100 degrees C for 1 or 5 min. Tumors were then incubated separately in media with 10% AC, OPEN, or heated OPEN group sera. In the third study, aliquots of sera from the OPEN group mice were dialyzed against PBS through a 3.5-kD or an 8-kD dialysis membrane tubing for 24 h. Tumors were then incubated separately in media with 10% AC, OPEN, or dialyzed OPEN group sera. For both experiments, tumor proliferation was determined and compared between groups after 72 h of incubation. RESULTS: Tumor cells incubated with POD2 and POD4 sera from OPEN group mice proliferated twice as fast as those incubated with sera from either AC or INS group mice. The difference in proliferation was maximal on POD4 and started to decline by POD7. Proliferative activity from the OPEN group sera decreased significantly when heated for 1 min and was completely ablated after 5 min of heating. Proliferative activity from the OPEN group sera was completely ablated after dialysis. CONCLUSIONS: We conclude that there is a serum-soluble factor(s) present postoperatively that stimulates tumors to grow significantly faster after laparotomy. The mitogenic effect of laparotomized mice sera is dilutable. It is uncertain whether the factor is heat labile, since heating most likely destroys other necessary proteins in the sera. The size of the factor is undeterminable using the dialysis method. Further efforts to identify these factors are currently underway.

Lymphocyte proliferation in mice after a full laparotomy is the same whether performed in a sealed carbon dioxide chamber or in room air.

PURPOSE: Our laboratory has demonstrated that significantly more cell-mediated immunosuppression occurs after full laparotomy than after either anesthesia control or carbon dioxide (CO2) pneumoperitoneum. We further demonstrated that the postoperative immunosuppression is related to the length of the incision. Other investigators believe that the immunosuppression observed after laparotomy is caused by peritoneal exposure to small amounts of lipopolysaccharide found in circulating air. They believe that the better-preserved immune function associated with laparoscopic surgery results from the avoidance of air contamination of the peritoneal cavity. To investigate this hypothesis, we determined and compared postoperative lymphocyte proliferation rates after (a) laparotomy in room air, (b) laparotomy in a CO2 chamber, (c) CO2 insufflation in a murine model, and (d) anesthesia alone. METHODS: Female C3H/He mice (n = 21) were divided randomly into four groups: (a) anesthesia control, (b) air laparotomy, (c) CO2 laparotomy, and (d) CO2 insufflation. The control mice underwent no procedure. The group 2 animals underwent a full midline incision (xiphoid to pubis) and exposure to room air for 20 min and then were clipped closed. The group 3 mice underwent a full midline incision in a sealed CO2 chamber for 20 min, and the group 4 mice insufflation with CO2 gas at 4 to 6 mm Hg for 20 min. Splenocytes were harvested from all the animals on day 2 after the interventions. Lymphocyte proliferation then was assessed using the nonradioactive colorimetric MTS/PMS system 72 h after concanavalin-A stimulation. RESULTS: There was no significant difference in lymphocyte proliferation between the air and CO2 laparotomy groups. Lymphocyte proliferation in the anesthesia control and CO2 insufflation groups was significantly higher than in both the air laparotomy (p<0.05) and CO2 laparotomy (p<0.05) groups (p values by Tukey-Kramer test). There was no significant difference between the anesthesia control and CO2 pneumoperitoneum groups. CONCLUSIONS: Our results suggest that full laparotomy performed in a sealed CO2 chamber compared to room air laparotomy resulted in similar suppression of lymphocyte proliferation. Furthermore, no significant suppression of lymphocyte proliferation was observed in the CO2 pneumoperitoneum group. These results, with regard to lymphocyte proliferation rates, refute the hypothesis that postoperative immunosuppression is related to air exposure and support the alternative hypothesis that immunosuppression is related to incision length.

Time course of differences in lymphocyte proliferation rates after laparotomy vs CO(2) insufflation.

BACKGROUND: Our laboratory has previously demonstrated that cell-mediated immune function is significantly more suppressed after both laparotomy and laparoscopic-assisted bowel resection than after peritoneal insufflation or open bowel resection, as assessed by delayed-type hypersensitivity (DTH) response. The purpose of this study was to further evaluate cell-mediated immunity by examining lymphocyte proliferation rates after laparotomy vs CO(2) insufflation. METHODS: Female Balb/C mice (n = 75) were randomly divided into the following three groups: (a) anesthesia control (A/C), (b) CO(2) insufflation (INS), and (c) sham laparotomy (OPEN). The A/C group mice underwent no procedure. The INS group underwent insufflation with CO(2) gas at 4-6 mmHg for 20 min. The OPEN group underwent a midline incision from xiphoid to pubic symphysis, which was clipped closed after 20 min. Splenocytes were obtained via splenic harvest and lymphocyte isolation on postoperative days (POD) 1, 2, 3, 4, and 8. Lymphocyte proliferation was determined by a nonradioactive colorimetric MTS/PMS assay 72 h after concanavalin A stimulation. RESULTS: The laparotomy group's lymphocyte proliferation rates were significantly lower than both the control and the insufflation groups on POD 2, POD 3, and POD 4. On POD 1 and POD 8, there were no significant differences in lymphocyte proliferation among the three groups. No differences were found between the control and insufflation groups at any point. CONCLUSIONS: After stimulation, lymphocytes proliferate at a lower rate after laparotomy than after CO(2) insufflation. Significant differences in lymphocyte proliferation rates between groups persist at least through POD 4. By POD 8, the mean lymphocyte proliferation rate in the laparotomy group was back to the baseline level. Our results suggest greater immunosuppression after sham laparotomy than after CO(2) insufflation.

An in vitro model of T cell activation by autologous cytomegalovirus (CMV)-infected human adult endothelial cells: contribution of CMV-enhanced endothelial ICAM-1.

Cellular immunity is strongly implicated in control of CMV disease; however, many mechanistic details remain unresolved. We previously demonstrated T cell activation responses to CMV-infected allogeneic endothelial cells (EC), suggesting EC as a mediator of CMV response in the transplant recipient. We now test the hypothesis that CMV-specific T cell responses can be directly stimulated by infected EC in an environment free of potentially confounding allogeneic factors. By isolating splenic T cells and gonadal vein endothelial cells (GVEC) from individual cadaveric organ donors, we have developed an in vitro model of T cell interaction with autologous CMV-infected EC. Proliferation assays demonstrated significantly enhanced responses by CMV-seropositive donor-derived T cells cocultured with CMV-infected GVEC, as compared with those elicited by uninfected cells. Similarly, as determined by limiting dilution analysis of IL-2-producing cells, T cell response frequencies to infected GVEC were significantly greater than to uninfected EC. In contrast, responses of CMV-seronegative donor-derived T cells were minimal, regardless of CMV status of stimulator GVEC. Intriguingly, CD4 responses were observed in spite of the fact that CMV-infected EC express no HLA class II. Finally, attenuation of CMV-stimulated T cell proliferation observed in the presence of blocking Ab specific for ICAM-1 suggests a contributing role for CMV-enhanced endothelial ICAM-1 expression in the activation response. These studies demonstrate that EC can stimulate autologous T cell responses to CMV in the absence of accessory APC and suggest potentially novel mechanisms of immune activation.

Prevention of acute murine cardiac allograft rejection: anti-CD4 or anti-vascular cell adhesion molecule one monoclonal antibodies block acute rejection but permit persistent graft-reactive alloimmunity and chronic tissue remodelling.

We treated C57BL/6 mouse recipients of DBA/2 cardiac allografts with anti-CD4 monoclonal antibodies (mAb) or anti-vascular cell adhesion molecule 1 mAb to promote long-term allograft survival and subjected both the recipient animals and the long-surviving allografts to a battery of histologic and immunologic tests. The results were similar regardless of the mAb used for antirejection therapy. At all tested times after transplantation, the allografts displayed histologic evidence of ongoing microvascular endothelial activation and interstitial leukocytic infiltration. Reverse transcription polymerase chain reaction analyses revealed continuous intragraft expression of messenger RNA for interleukin 1, interleukin 2, interleukin 4, interleukin 6, tumor necrosis factor, interferon gamma, and transforming growth factor beta. All grafts had histologic evidence of ongoing vascular and parenchymal tissue remodeling, including interstitial fibrosis and vascular neointimal hyperplasia. The graft recipients retained limiting dilution analysis--detectable, donor-reactive cytolytic T lymphocyte, and helper T lymphocyte in their spleens and produced high liters of donor-reactive alloantibodies. Variable amounts of allogeneic microchimerism were detectable in some, but not all of the long-surviving graft recipients. In general, these observations indicate that (1) a similar immune status is achieved in long-surviving allografts and their recipients when either anti-CD4 mAb or anti-vascular cell adhesion molecule-1 mAb was used for antirejection therapy, in spite of the major differences in lineage and distribution of cells targeted by these two mAbs, (2) this immune status is characterized by continuous, long-term inflammatory and immune processes very similar to those observed during acute allograft rejection, and (3) in spite of these processes the allografts continue to function, although they invariably develop a chronic rejection-like histopathologic condition that may ultimately limit graft function. In this regard, the recipients of long-surviving allografts do not seem to be tolerant of their graft alloantigens.

Regulation of endothelial VCAM-1 expression in murine cardiac grafts. Expression of allograft endothelial VCAM-1 can be manipulated with antagonist of IFN-alpha or IL-4 and is not required for allograft rejection.

This report provides evidence to support the hypothesis that tumor necrosis factor-alpha (TNF-alpha) and IL-4 promote the expression of new endothelial surface molecules in rejecting murine heterotopic cardiac allografts. The microvascular endothelia of these cardiac allografts all develop strong reactivity with the monoclonal antibodies (mAbs) YN1.1/74 (anti-ICAM-1), M/K-2 (anti-VCAM-1) and MECA-32 (undefined molecule) within 3 to 5 days of graft implantation. Daily treatment of the allograft recipients with pentoxifylline (PTX), soluble TNF receptor (TNFR:Fc), anti-interleukin-4 (IL-4) mAb (11B11), or soluble IL-4 receptor, each abrogate the expression of endothelial VCAM-1 and reduce the endothelial reactivity with the mAbs YN1.1/74 and MECA-32 to levels found in cardiac isografts. This is accompanied by a reduction, but not an elimination, of interstitial leukocytic infiltration. Despite this, cardiac allograft recipients treated with PTX or the mAb 11B11 rejected allografts at the same rate as untreated allograft recipients, ie, within 10 to 12 days after graft implantation. These rejected grafts contained mRNAs for TNF-alpha and IL-4, as well as for all other cytokines that have been associated with rejecting allografts. This suggests that endothelial VCAM-1 expression, which is characteristic of rejection, is not an essential element of the rejection process. Interestingly, the grafts from the PTX-treated recipients continued to display rare, isolated VCAM-1 positive cells in the interstitium, which may be dendritic cells. In general, these studies demonstrate a role for IL-4 and TNF-alpha in the alterations of vascular endothelial phenotype observed in rejecting cardiac allografts. They also demonstrate that endothelial VCAM-1 expression is not essential for the allograft rejection process, and that the role of VCAM-1 in this process may be more subtle than was initially suspected.