Thoracic reconstruction with the omentum: indications, complications, and results

This study provides a retrospective analysis of 60 patients who underwent thoracic reconstruction with the omentum. Patients were identified by searching several databases to determine demographics, indications for surgery, operative technique, and postoperative course, including donor and recipient site morbidity. From January 1975 to May 2000, the authors harvested and transferred the omentum successfully (57 pedicled, 3 free) in 60 patients (mean age, 60 years; age range, 21-86 years) for sternal wound infections (N = 34), chest wall resections (N = 17), pectus deformities (N = 2), intrathoracic defects (N = 4), and breast reconstruction (N = 3). The omentum was used as a primary flap in 39 patients and as a salvage flap in 21 patients. Average operative time was 3.9 hours and average hospital stay was 34.3 days. Partial flap loss occurred in 7 patients, with no total flap failures. Morbidity included six abdominal wound infections and seven epigastric hernias. Mortality was 11.7%. The omentum can be harvested safely and used reliably to reconstruct varying thoracic wounds and defects. Specific indications from this series include osteoradionecrosis, chest wall tumors, massive sternal wounds, and refractory mediastinitis. Hultman CS, Culbertson JH, Jones GE, et al. Thoracic reconstruction with the omentum: indications, complications, and results.

Chiari malformation, cervical spine anomalies, and neurologic deficits in velocardiofacial syndrome

The purpose of this investigation was to evaluate the prevalence of Chiari malformation, cervical spine anomalies, and neurologic deficits in patients with velocardio-facial syndrome. This study was a prospective evaluation of 41 consecutive patients with velocardiofacial syndrome, documented by fluorescence in situ hybridization, between March of 1994 and September of 1998. The 23 girls and 18 boys ranged in age from 0.5 to 15.2 years, with a mean age of 6.7 years. Nineteen patients were assessed with magnetic resonance imaging, 39 underwent lateral cephalometric radiography, and all patients were examined for neurologic deficits. Eight of 19 patients (42 percent) had anomalies of the craniovertebral junction, including Chiari type I malformations (n = 4), occipitalization of the atlas (n = 3), and narrowing of the foramen magnum (n = 1). One patient with Chiari malformation required suboccipital craniectomy with laminectomy and decompression. Fourteen of 41 patients (34 percent) had demonstrated neurologic deficits; 10 patients (24 percent) had velar paresis (6 unilateral and 4 bilateral). Chiari malformations, cervical spine anomalies, and neurologic deficits are common in velocardiofacial syndrome. Because these findings may influence the outcome of surgical intervention, routine assessment of patients with velocardiofacial syndrome should include careful orofacial examination, lateral cephalometric radiography, and magnetic resonance imaging of the craniovertebral junction.

The effector component of the cytotoxic T-lymphocyte response has a biphasic pattern after burn injury

INTRODUCTION

Burn injury delays allograft rejection and impairs the host defense against infection. These functions are mediated via the cytotoxic T-lymphocyte (CTL) response. The CTL response is divided into antigen recognition/processing and effector phases. Presensitization allows selective analysis of changes, induced by burn injury, in the effector limb of the CTL response in relation to time and burn size.

METHODS

Anesthetized CBA mice were primed with either a flank allograft from C57BL/6 (B6) mice or an autograft (negative control). Five weeks after grafting, animals were anesthetized and received either a 0, 20, or 40% burn. Spleens were harvested 3, 7, 10, and 14 days after burn injury (n = 96), cocultured with B6 stimulator splenocytes, and assessed for CTL response to radiolabeled allogeneic targets in a 51Cr release assay. In experiment 2, spleens were harvested from unburned and 40% burned animals on Postburn Days 3 and 14. After triple staining, cells were analyzed by flow cytometry for CD4, CD8, and CD25 antigens. In experiment 3, splenocytes from 0 and 40% burned animals on Postburn Days 3 and 14, were cocultured with B6 stimulators for 5 days. Supernatants were evaluated for interleukin (IL)-2, IL-5, and interferon-gamma (IFN-gamma) using ELISA:

RESULTS

The CTL response for 20 and 40% burned animals decreased 3 days postburn (-11.9 and -30.1%, P < 0.05), returned to baseline in 7-10 days, and was increased by 14 days postburn (15.8 and 22.6%, P < 0.05). The T-helper lymphocyte population (CD4) from 40% burn animals was significantly decreased on Postburn Days 3 and 14 (10.12 +/- 0.45% vs 11.78 +/- 0.29% and 10.19 +/- 0.24% vs 14.21 +/- 0.97%, respectively, P < 0.05). The CTL effector (CD8) splenocyte population was significantly higher in the burned animals on Postburn Day 14 (4.55% vs 3.71%, P < 0.05). On Postburn Day 3, average IL-5 production was higher in the burned animals (1.80 pg/ml vs 0.59 pg/ml, respectively, P < 0.05). The burn group, on Postburn Days 3 and 14, showed a decrease in mean IL-2 production (212.81 pg/ml vs 263.6 pg/ml and 342.7 pg/ml vs 421.4 pg/ml, respectively, P < 0.05). Mean IFN-gamma production on Postburn Days 3 and 14 was decreased in burned mice (263.75 pg/ml vs 285.57 pg/ml and 218.16 pg/ml vs 263.42 pg/ml, P < 0.05).

CONCLUSIONS

Burn injury impairs the effector limb of the CTL response as a function of burn size in the immediate postburn period. CTL activity returns to baseline within 7-10 days postburn and has a rebound increase by Day 14. Early CTL suppression, after burn injury, may be due to a decrease in the T-helper subpopulation. The late increase in cytotoxicity may be secondary to an increase in the effector CTL population in the late postburn period. Burn injury causes a T-helper-2 phenotype as demonstrated by depressed IL-2 and IFN-gamma production and increased IL-5 production.

Immunogenicity of cultured keratinocyte allografts deficient in major histocompatibility complex antigens

BACKGROUND

Full-thickness (FT) and cultured keratinocyte (CK) allografts have been used as temporary skin replacements in patients with massive burns, but these grafts are ultimately rejected after restoration of host immunocompetence. Genetic engineering has permitted the creation of knockout (KO) mice deficient in class I or class II major histocompatibility antigens. This study examines the immunogenicity of such grafts to determine if these genetically modified keratinocytes could be used for permanent wound coverage.

METHODS

Host sensitization to alloantigen was assessed by second-set rejection. CBA mice (n = 111) were primed with flank grafts consisting of FT and CK allografts from normal C57BL/6 donors, FT and CK class I KO allografts, FT and CK class II KO allografts, and CK autografts. Three weeks later, hosts were challenged with normal tail allografts and observed for second-set rejection. Median graft survival was analyzed by chi2 and Wilcoxon rank tests. In the second experiment, cytotoxic T lymphocytes (CTLs) were harvested from CBA mice (n = 28) 3 weeks after flank grafting. CTL effectors were tested on radiolabeled targets at various ratios in a 51Cr release assay. Dilution curves of CTL activity were compared by analysis of variance.

RESULTS

Hosts primed with CK or FT allografts demonstrated accelerated rejection of second-set tail grafts compared with hosts covered with CBA autografts. CK knockout grafts were less immunogenic than FT knockout skin; class II KO allografts were considerably less immunogenic than class I KO allografts. CTL activity against the knockout CK allografts was negligible compared with that of hosts primed with normal allografts or FT knockout allografts.

CONCLUSION

Although full-thickness knockout skin retains substantial immunogenicity, cultured keratinocytes deficient in class II antigens fail to prime for accelerated second-set rejection and do not elicit a CTL response in the graft recipient. This lack of immunogenicity may permit the indefinite survival of allogeneic knockout keratinocytes in patients requiring massive wound excision and coverage.

Return to jeopardy: the fate of pediatric burn patients who are victims of abuse and neglect

Child abuse and neglect continue to account for a significant number of pediatric burn injuries. Although the epidemiology of intentional burn injuries has been studied, this report compares victims of abuse with victims of neglect. Furthermore, we investigate the long-term fate of both victim and perpetrator. A retrospective search of the North Carolina Jaycee Burn Center database identified 21 abuse and 21 neglect patients among 238 pediatric admissions (mean age, 5.4 years, mean surface area 14%) from 1992 to 1994. The medical, social, and legal records of each patients were examined by two independent reviewers. History, hospital course, and disposition were compared between groups by chi-square analysis and Student's t test. Compared with victims of neglect, abused children were slightly younger (2.1 vs 2.7 years), had somewhat larger burns (12.3% vs 9.05 total body surface area), had inconsistent mechanisms of injury (90% vs 33%, p < 0.002) that were bathroom related (81% vs 29%, p < 0.001), were likely to have a history of abuse (57% vs 24%, p < 0.05) or stigmata of abuse on exam (43% vs 14%, p < 0.05), had longer lengths of stay (23.8 vs 14.1 days, p < 0.05), had similar complication rates, and were place more often in foster care (65% vs 15%, p < 0.01). Inpatient mortality was 5%. Mean follow-up was 108 days, during which time two children were readmitted for repeat abuse. Regarding the caregivers, 57% were single mothers, 36% had been investigated for abuse or neglect, and 12% had lost custody of other children. Of the perpetrators involved in abuse, 71% were charged with a felony, 43% were convicted, and 19% were incarcerated longer than 30 days. Victims of burn abuse and neglect differ considerably in terms of history and disposition but not hospital course. Children in both groups, however, remain at risk for abuse and neglect after discharge. We recommend that more aggressive efforts be made to secure safe environments for these children and that the perpetrator, if clearly identified, be dealt with in a fashion to prevent recurrence of the offense.

Host priming, not target antigen type, decides rejection rate in mice primed with MHC II "knockout" cultured keratinocytes

BACKGROUND

Lack of skin for autograft continues to be problematic in patients with large burns. Allograft and xenograft have been used, but are prone to rapid rejection. Use of cultured keratinocytes (CK) and major histocompatibility complex (MHC) II "knockout" grafts leads to prolonged graft survival compared to allograft. Whether this prolongation is secondary to decreased priming efficacy or target recognition is unknown. Whether a combination of these techniques would generate a less immunogenic allograft remains to be determined.

METHODS

CBA mice (n = 100) were flank-grafted with full thickness C57BL/6 (B6 FT), B6 cultured keratinocytes (B6 CK), B6 major histocompatibility complex II "knockout" full thickness (KO II FT), B6 major histocompatibility complex II "knockout" cultured keratinocytes (KO II CK), or a full thickness autograft (Auto). Three weeks after priming flank grafting, B6, MHC I (KO I), and KO II full thickness tail grafts were placed on each mouse. Tail graft rejection was assessed daily by an observer blinded to flank and tail-graft type. A 4-point grading system for graft color, hair loss, and texture was used.

RESULTS

Animals primed with KO II CK flank grafts had increased survival of tail grafts over B6 FT flank grafted controls (12.3 +/- 1.05 vs 10.1 +/- 1.00, P < 0.05). Within flank graft groups, however, B6, KO I, and KO II tail graft survival was similar.

CONCLUSIONS

KO II CK allografts decrease host priming compared to normal B6 FT allograft. MHC deletion (KO I or KO II) does not protect a target graft from rejection in a primed host. CK and KO techniques may offer a less immunogenic allograft and a readily available source of wound coverage in patients with extensive burns.

Early but not late burn wound excision partially restores viral-specific T lymphocyte cytotoxicity

OBJECTIVE

Early burn wound excision restores immunocompetence and improves patient survival, but the exact mechanisms have not yet been defined. Burn injury impairs cytotoxic T lymphocyte (CTL) activity as a function of burn size, increasing the risk of infection. The purpose of this study was to determine if early wound excision improved viral-specific CTL function.

METHODS

Anesthetized C57BL/6 mice (n = 20) received 0%, 20%, or 40% total body surface area full-thickness contact burns and were inoculated 3 days later with intraperitoneal lymphocytic choriomeningitis virus. Eight days after infection, or 11 days after burn, CTL effectors (E) were harvested and tested against infected, radiolabeled L-Dh targets (T) in a 51Cr-release assay, at varied E:T ratios. Dilution curves of CTL activity were compared by analysis of variance. In the second experiment, mice (n = 18) underwent a 30% burn that was totally excised and grafted on postburn days (PBDs) 0, 3, and 7. Control groups included sham burn and no excision of a 30% burn. In the third experiment, mice (n = 22) received a 30% burn that was partially, completely, or not excised on PBD 3. Control groups included sham burn with and without excision. All groups were infected with intraperitoneal lymphocytic choriomeningitis virus on PBD 3. Viral-specific CTL activity was determined on PBD 11.

RESULTS

Both 20% and 40% burn injury impaired viral-specific CTL function. Wound excision on PBDs 0 and 3, but not on PBD 7, partially restored CTL function. Total excision of the 30% burn improved CTL activity to a greater extent than did partial excision.

CONCLUSION

Burn injury inhibits viral-specific CTL activity. Early, complete wound excision augments CTL function. Improved CTL activity after burn may reduce the risk of infection, providing an immunologic rationale for expeditious wound excision.

Statewide, population-based, time-series analysis of the frequency and outcome of pulmonary embolus in 318,554 trauma patients

The low occurrence, nonspecific signs and symptoms, and high rate of associated morbidity and mortality of pulmonary embolus (PE) create major problems in the prevention, diagnosis, and treatment of PE. The purpose of this study was to analyze the frequency and outcome of PE in an entire state's trauma population using a large, population-based, hospital discharge data base. With the inclusion of an entire population, the reported incidence, high risk groups of patients, and specific risk factors regarding PE were assessed. A multivariate, logistic regression model was created from the data to determine predictive power of selected risk factors in patients at risk.

METHODS

The data source was a statewide, hospital discharge data base that includes data on all hospitalized patients for all of the hospitals in North Carolina. Data were available from 1988 to 1993. Using primary discharge diagnosis and nine additional ICD-9 coded diagnoses from the discharge abstract, patients were selected by presence of diagnostic codes for traumatic injury (800-959.9) and PE (415.1). Statistical analysis was performed using univariate and multivariate analysis to determine significant risk factors and to create a candidate model for the prediction of risk in the study population.

RESULTS

Of 318,554 patients, 952 (0.30%) had a recorded diagnosis of PE. The mortality rate for patients with PE (26%) was 10 times higher than the mortality rate in patients without PE (2.6%). In evaluating specific risk factors, age was a significant predictor of the risk of PE: 0.05% for patients under age 55 and 0.7% in those 55 years and over. The rate of PE, 0.3%, was low for the entire study population, but was highest in patients with injuries of the extremities, 0.53%. Increasing Injury Severity Score and Abbreviated Injury Scale score for determined body systems were also found to correlate with an increasing risk of PE. Over the course of the study, the incidence of PE among patients discharged from non-trauma centers showed a significant decrease. There was also a decrease in the mortality in non-trauma centers for PE. This finding cannot be due to coding changes coincident with the advent of diagnosis related groups because it would be associated with more vigorous combing of charts for diagnoses? It may well be that the use of prophylactic measures in injured patients initially used at trauma centers was adopted by the physicians at non-trauma centers over this time with the resultant decline in PE and associated mortality. From the univariate linear regression models, a logistic regression model was created that confirmed age as the most significant risk factor, followed by Injury Severity Score and Abbreviated Injury Scale score for soft tissue, extremity, and chest. The calculated area under the receiver operator characteristic curve was 0.72.

CONCLUSION

Using a large, population-based data base, we were able to determine the reported incidence of PE among trauma patients and establish specific risk factors. The reported incidence of PE in this population is low, 0.30%. The mortality among those with PE, however, is significant at 26%. In this study, age, Injury Severity Score, and injury to specific body regions (soft tissue, extremity, chest) were associated with an increased risk of PE. The investigation of prophylaxis of PE and the general management of injured patients may be influenced by the overall low reported frequency of PE and the specific high risk populations described in this study. In light of the low incidence of PE in patients without specific risk factors, prophylactic interventions cannot be routinely recommended unless their benefits clearly outweigh their risks.

Effect of cyclo-oxygenase inhibition on in vitro B-cell function after burn injury

The role of PGE2 in suppression of B-cell function after burn injury was investigated. Splenocytes from burned or sham-burned mice were isolated 8 days after burn injury and cultured with lipopolysaccharide with or without the addition of prostaglandin E2 (PGE2) or indomethacin (Indo). Anti-peptidoglycan polysaccharide immunoglobulin (Ig)M (specific antibody to a bacterial antigen), total IgM, and total IgG levels in culture supernatant and lymphocyte proliferation were measured. All B-cell functions were significantly suppressed by burn injury. PGE2 suppressed all B-cell functions except for IgG synthesis. Indo restored anti-peptidoglycan polysaccharide IgM to normal levels, but did not have a significant effect on suppressed proliferation and total IgM synthesis. IgG synthesis was increased by PGE2 and inhibited by Indo. Although not all B-cell suppression was accounted for by PGE2, this prostaglandin appeared to be a mechanism responsible for impaired antigen specific antibody response and isotype switching. Successful restoration of specific antibody synthesis to bacterial antigen suggests a potential therapeutic role for a cyclo-oxygenase blocking agent after burn injury.

Allogeneic fibroblasts used to grow cultured epidermal autografts persist in vivo and sensitize the graft recipient for accelerated second-set rejection

INTRODUCTION

Cultured epidermal autografts (CEAs) have been used for wound coverage in patients with massive burns and other skin defects. However, CEAs often display late breakdown, which may be immunologically mediated and initiated by persistent foreign fibroblasts used as a feeder layer to optimize keratinocyte growth. This study investigates whether these fibroblasts, previously shown to persist in vitro, survive after grafting and induce host sensitization to alloantigen.

METHODS

CEAs from CBA donors (H-2k) were grown on allogeneic NIH 3T3 (H-2q) or syngeneic LTK (H-2k) fibroblasts, which were removed by trypsinization 7 days later. CBA mice (n = 85) were flank-grafted with NIH allografts (positive control), CEA/3T3s, CEA/LTKs, or CBA autografts (negative control). Hosts were challenged with second set NIH tail allografts 3 weeks later. Median graft survival was compared between groups by Wilcoxon rank and chi 2 analysis. Additional CBA mice (n = 15) received CEAs that were biopsied 0, 4, and 8 days after grafting. The presence of allogeneic fibroblasts was determined by Western immunoblotting, using KL295, a monoclonal antibody that recognizes H-2q (but not H-2k) class II histocompatibility antigens.

RESULTS

Allogeneic fibroblasts persisted after grafting but decreased over time, as determined by alloantigen expression on Western immunoblots. Accelerated tail graft rejection occurred in hosts primed by NIH allografts (9 days, p < 0.05), as well as by CEAs growth with an allogeneic (10 days, p < 0.05) but not a syngeneic feeder layer (12 days, NS). Mice receiving flank autografts rejected second set tail allografts at 12 days.

CONCLUSIONS

Immunogenic fibroblasts used to grow CEAs survive in vivo and sensitize the graft recipient for accelerated second-set rejection. These persistent cells may initiate an inflammatory response that may result in late graft breakdown and limit the utility of CEAs grown with a foreign fibroblast feeder layer.

Immediate burn wound excision restores antibody synthesis to bacterial antigen

Although burn wound excision and grafting have been shown to improve patient survival, the effects on immune function, especially humoral immunity, are not completely understood. The purpose of this study was to investigate the effect of immediate and early wound excision on antibody synthesis and B-cell proliferation, specifically, antibody response to PGPS, a ubiquitous bacterial cell wall antigen. Thirty-six male BALB/c mice were divided into four groups. Sham mice received no burn, and remaining mice received a 30% body surface area full-thickness burn. Under general anesthesia, excision and grafting was performed either 6 or 72 hr after injury (BE&G6 and BE&G72 groups). A fourth control group received burn but did not undergo excision and grafting (Burn group). Splenocytes were isolated 8 days postburn and stimulated with 2.5 microgram/ml lipopolysaccharide. Anti-PGPS IgM, total IgM, and total IgG levels were determined by ELISA. B-cell proliferation, measured by [3H]-thymidine uptake, was expressed as stimulation index. All B-cell functions were significantly suppressed by burn injury. Immediate excision and grafting (BE&G6) restored anti-PGPS IgM synthesis to normal, while nonspecific B-cell functions did not change significantly. Early excision and grafting (BE&G72), however, failed to significantly improve any B-cell functions. Immediate but not early BE&G restored antibody synthesis to the bacterial cell wall antigen (PGPS). Immediate BE&G may therefore lead to a decrease in bacterial infection after burn injury.

The efficacy of percutaneous cholecystostomy in critically ill patients

Percutaneous cholecystostomy (PC) has been proposed as a method of biliary decompression in critically ill patients with acute cholecystitis. We evaluated the efficacy of PC in this setting. The charts of 33 critically ill patients (mean age 52, range 5-87) who underwent PC for suspected acute cholecystitis were retrospectively examined. Univariate analysis was performed to identify which patients might benefit from PC. PC was technically successful in all patients with no direct mortality or major complications. Failure to improve within 24 hours was associated with increased mortality (P = 0.02). A total of 22/33 patients improved, 17/33 survived, and 8/33 required surgery. PC delayed definitive operation in two patients. Cholelithiasis was associated with surgical intervention (P = 0.01) but not increased mortality. Favorable prognosticators for survival included gallbladder dilatation (P = 0.01), pericholecystic fluid (P = 0.01), and absence of a pulmonary artery catheter (P = 0.02). Predictors of improvement included gallbladder nonvisualization on hepatobiliary scan (P = 0.047), positive bile cultures (P = 0.017), and initial drainage of < / = 100 cc (P = 0.009). Age, laboratory data, the use of total parenteral nutrition, and intubation did not predict outcome. Nine positive bile cultures prompted antibiotic changes in five cases. Finally, PC was less expensive than open cholecystostomy ($1620 versus $3155). PC is a safe, cost-effective, minimally invasive procedure that has diagnostic and therapeutic value in critically ill patients with acute cholecystitis. The involvement of a general surgeon is important to ensure that those patients who do not improve within 24 hours receive early surgical intervention and provide long-term definitive care for those patients with cholelithiasis.

The 1995 Moyer Award. The effect of burn injury on allograft rejection, alloantigen processing, and cytotoxic T-lymphocyte sensitization

Burn injury impairs cellular immunity, increases the risk of viral infection, and delays allograft rejection, but little is known about its effect on antigen processing and cytotoxic T-lymphocyte (CTL) function. This study examined the effect of burn injury on alloantigen sensitization with an in vivo model of second-set rejection and in vitro assays of CTL alloreactivity. Anesthetized CBA mice (n = 95) received a 0%, 20%, or 40% full-thickness contact burn that was partially excised 3 days later and covered with autograft or C57BL/6 allograft. Two weeks after the burn was inflicted, mice were challenged with second-set tail allografts, which were observed for rejection. Median graft survival times were compared by Wilcoxon rank and chi-squared analysis. Additional CBA mice (n = 24) underwent similar burn injury, excision, and grafting. Splenocytes were harvested 2 weeks later and were used as CTL effectors against radiolabeled targets. Dilution curves of target lysis were compared by analysis of variance. Forty percent burn injury prolonged unprimed allograft survival from 13 to 15 days (p < 0.01) but had a greater effect on primed allograft survival, which increased from 9 to 12.5 days (p < 0.01). Furthermore, a 40% burn eliminated the influence of priming, resulting in second-set graft survival similar to that of mice in an unburned, unprimed control group (12.5 vs. 13 days, NS). Whereas 20% burn injury did not inhibit CTL priming, a 40% burn profoundly impaired CTL function (p < 0.001), which recovered only after 6 days of in vitro allostimulation. Burn injury inhibits both alloantigen priming and the immunologic memory of CTLs as a function of burn size. This impairment in alloantigen processing helps to explain defects in cellular immunity and suggests a mechanism for prolonged allograft survival and decreased viral resistance after burn injury occurs.

Burn injury impairs second-set rejection and CTL reactivity in mice primed by cultured keratinocyte allografts

Cultured keratinocyte (CK) allografts have limited antigenicity and have been used as a skin replacement in patients with massive thermal injury. Recent data indicate that CK grafts are more immunogenic than previously believed and could compromise wound healing in the immunocompetent host. The purpose of this study was to determine if the immunosuppression of burn injury might affect the alloantigen response and minimize sensitization to CK allografts. CBA mice received a 0%, 20%, or 40% burn that was partially excised three days later and grafted with a full-thickness (FT) skin allograft, CK allograft, or CK autograft. Two weeks postburn, mice received FT tail skin allografts, which were observed for rejection. We observed that FT and CK allografts primed the unburned host with equal efficacy. However, burn injury selectively minimized priming by CK allografts, resulting in delayed rejection of second-set allografts. With evidence that burn injury inhibits host sensitization to CK allografts, we then examined the effect of burn size on CTL alloreactivity. Additional CBA mice underwent burn injury, excision, and grafting as described above. Host splenocytes were harvested two weeks later and tested on radiolabeled targets for allospecific cytotoxicity. CTLs from unburned mice primed with FT allografts demonstrated the greatest CTL lysis, followed next by CTLs from unburned mice covered with CK allografts. Burn injury inhibited CTL activity as a function of wound size. Activity of CTLs from burned mice primed with CK allografts improved after in vitro allostimulation but remained below that of CTLs from unburned, unprimed mice. We conclude that burn injury selectively inhibits the allospecific response to CK allografts. The decreased immunogenicity of CK allografts, when used for burn wound coverage, may improve the long-term survival of allogeneic keratinocytes, enhancing their potential as a biologic skin replacement.

The relationship between interferon-gamma and keratinocyte alloantigen expression after burn injury

BACKGROUND

Cultured keratinocyte (CK) and cadaveric skin allografts have prolonged survival in patients with massive thermal injury. It is unclear if this delayed rejection is due to impaired host responsiveness or decreased graft immunogenicity. Although burn injury has been shown to decrease parameters of allograft response, no studies have examined the effect of burn injury on alloantigen expression. This study investigated the effect of burn size on class II antigen expression in CK allografts as well as on tissue levels of interferon-gamma (IFN-gamma), the principle regulator of alloantigen expression.

METHODS

Anesthetized CBA mice (n = 64) received a 0%, 20% partial-thickness (PT), 20% full-thickness (FT), or 40% FT contact burn. Forty-eight hours later, wounds were partially excised and covered with CK allografts from C57BL/6 donors. Five days after burn injury, grafts were analyzed for donor-specific class II antigen. Protein expression was determined by Western immunoblotting and quantified with video densitometry. Wound, serum, and unburned skin levels of IFN-gamma were determined by enzyme-linked immunosorbent assay. Groups were compared by Fisher's analysis of variance.

RESULTS

As burn size increased, class II antigen expression decreased (p < 0.001). This corresponded with decreased wound and skin levels of IFN-gamma after 40% burn (p < 0.05); however, wound IFN-gamma was significantly elevated after 20% PT and FT burns (p < 0.01). Serum IFN-gamma increased as burn size increased (p < 0.01).

CONCLUSIONS

Burn injury decreases the antigenicity of CK allografts, which partly explains delayed allograft rejection after burn injury. Although wound IFN-gamma increases after minor thermal injury, the profound decrease in wound and skin IFN-gamma after a major burn corresponds with diminished class II antigen expression. The decreased availability of IFN-gamma after major thermal injury provides a mechanism for limited allograft tolerance.

Early, complete burn wound excision partially restores cytotoxic T lymphocyte function

BACKGROUND

Cytotoxic lymphocytes (CTLs) are an important component of immune function, involved in antigen recognition and resistance to viral infection. Burn injury suppresses cell-mediated immunity, induces allograft tolerance, and increases the risk of viral infection, but the mechanisms are not well understood. This study analyzes the effect of burn size and burn wound excision on CTL activity.

METHODS

Anesthetized CBA mice (n = 12) received a 0%, 20%, or 40% body surface area contact burn. Additional mice (n = 16) received a 40% burn that was totally, partially, or not excised 72 hours after burn. Excised areas were covered with normal, syngeneic skin. Two weeks later harvested splenocytes were cocultured with allogeneic stimulators. CTL activity was determined by a 51Cr release assay, in which CTL effectors were tested on allogeneic, radiolabeled targets. Dilution curves of CTL activity were compared by ANOVA:

RESULTS

Both 20% and 40% burns significantly inhibited CTL activity (p < 0.05). Total but not partial excision of a 40% burn restored CTL activity (p < 0.01). Both total and partial wound excision also improved survival (p < 0.05).

CONCLUSIONS

Burn injury inhibits CTL activity in a size-dependent manner, and total wound excision significantly improves both CTL function and survival after injury. This study suggests a mechanism for the immunosuppressive effects of burn injury and provides an immunologic rationale for early, complete burn wound excision.

Xenogeneic mouse fibroblasts persist in human cultured epidermal grafts: a possible mechanism of graft loss

Recent reports suggest that long-term graft take of cultured epidermal autografts (CEAs) is less than 50% when late graft loss is considered. The characteristics of late CEA loss suggest that it may occur as a result of an immunologic reaction to persistent xenogeneic cells and/or proteins used to grow CEA. In this study we examined whether immunologically reactive, mouse 3T3 fibroblasts used as feeder layers can persist in primary, secondary, and tertiary human CEA. We cocultured keratinocytes from 11 separate burn patients with growth-arrested 3T3 fibroblasts. After removing visible 3T3 fibroblasts from CEA with trypsinization, we allowed CEA to reach confluence. We then harvested CEA either as primary, secondary, or tertiary cultures. We detected mouse fibroblasts using fluorescence activated cell sorting (FACS) with a monoclonal antibody specific for mouse major histocompatibility (MHC) antigens. We detected mouse MHC class II antigens by performing Western immunoblotting with another mouse MHC-specific monoclonal antibody. By FACS we identified mouse fibroblasts in 100, 75, and 62.5% of primary, secondary, and tertiary passage CEAs, respectively. Similarly by immunoblotting we found mouse MHC class II antigen in 100, 80, and 66.7% of primary, secondary, and tertiary CEAs. These results demonstrate that xenogeneic fibroblast feeder layers capable of generating immunogenic transplantation antigens persist in CEAs. The persistence of these cells and their antigen expression may contribute to CEA loss.

Transanal intestinal evisceration following suction from an uncovered swimming pool drain: case report

Transanal suction from a swimming pool drain can result in intestinal evisceration. We report the eighth such case, followed by a literature review, description of the mechanism, and management guidelines. This bizarre injury, which has devastating consequences for the children involved, is completely preventable by installation of semi-permanent, anti-vortex grates.