Major Variation in the Incidence of Appendicitis Before, During and After Pregnancy: A Population-Based Cohort Study.

BACKGROUND: Previous studies indicate a low incidence of appendicitis in third-trimester pregnancy, suggesting a protecting effect of pregnancy. This large population-based cohort study analyzes the association of appendicitis with pregnancy in more detail. The aim of the study was to investigate the incidence of appendicitis and negative appendectomy before, during and after pregnancy. METHODS: Cross-linking between two Swedish health registries provided data on appendectomy for all women in Sweden giving birth between 1973 and 2013. We analyzed the incidence rates (IR) of perforated and non-perforated appendicitis and negative appendectomy before, during and after pregnancy, and secular trends during the study period. Standardized incidence ratios (SIR) were estimated using age-, sex- and period-specific IR from the background population in Sweden. RESULTS: Some 3,888,452 pregnancies resulted in birth during the study period. An appendectomy was registered for 27,575 women in the interval starting one year before and ending two years after pregnancy. The incidence of appendicitis varied substantially during and after pregnancy. SIR for perforated appendicitis was 0.47 (95% CI 0.38-0.59) in the third trimester, 3.89 (2.92-5.18) peripartum, 2.20 (1.89-2.55) in the puerperium and 1.27 (1.19-1.36) in the year postpartum. The pattern was similar for non-perforated appendicitis. Negative appendectomy decreased postpartum. Incidence rate of non-perforated appendicitis and negative appendectomy decreased for both pregnant and non-pregnant women during the study period. CONCLUSIONS: The findings in this study suggest a protecting effect of pregnancy on the development of appendicitis, which is followed by a rebound effect after birth.

Predictive Factors for Postoperative Pancreatic Fistula-A Swedish Nationwide Register-Based Study.

BACKGROUND: A serious complication after pancreatoduodenectomy (PD) is postoperative pancreatic fistula (POPF). The aim of this study was to analyse the incidence and predictive factors for POPF by using a large nationwide cohort. METHODS: Data from the Swedish National Registry for Pancreatic and Periampullary Cancer for all patients undergoing a PD from 2010 until 30th June 2018 were collected. The material was analysed in two groups, no POPF and clinically relevant (grade B and C) POPF. RESULTS: A total of 2503 patients underwent PD, of which 245 (10%) developed POPF. Patients with POPF had significantly more overall complications (Clavien Dindo ≥3a, 75% vs. 21%, p < 0.001) and longer hospital stay (median 23 [16-35] vs. 11 [8-15], p < 0.001) than patients without POPF. The risk of POPF was higher with increased BMI (OR 1.08, p < 0.001). Preoperative presence of diabetes (OR 0.52, p = 0.012) and preoperative biliary drainage (OR 0.34, p < 0.001) reduced the risk of POPF. Reconstruction with pancreaticojejunostomy caused a more than two folded increase in POPF compared with pancreaticogastrostomy (OR 2.41, p < 0.001). Weight gain ≥2 kg on postoperative day 1 was also a risk factor (OR 1.76, p < 0.001). CONCLUSION: A high BMI, a pancreaticojejunostomy and postoperative weight gain were risk factors for developing POPF. Diabetes or preoperative biliary drainage was protective.

Randomized clinical trial of Appendicitis Inflammatory Response score-based management of patients with suspected appendicitis.

BACKGROUND: The role of imaging in the diagnosis of appendicitis is controversial. This prospective interventional study and nested randomized trial analysed the impact of implementing a risk stratification algorithm based on the Appendicitis Inflammatory Response (AIR) score, and compared routine imaging with selective imaging after clinical reassessment. METHOD: Patients presenting with suspicion of appendicitis between September 2009 and January 2012 from age 10 years were included at 21 emergency surgical centres and from age 5 years at three university paediatric centres. Registration of clinical characteristics, treatments and outcomes started during the baseline period. The AIR score-based algorithm was implemented during the intervention period. Intermediate-risk patients were randomized to routine imaging or selective imaging after clinical reassessment. RESULTS: The baseline period included 1152 patients, and the intervention period 2639, of whom 1068 intermediate-risk patients were randomized. In low-risk patients, use of the AIR score-based algorithm resulted in less imaging (19·2 versus 34·5 per cent; P < 0·001), fewer admissions (29·5 versus 42·8 per cent; P < 0·001), and fewer negative explorations (1·6 versus 3·2 per cent; P = 0·030) and operations for non-perforated appendicitis (6·8 versus 9·7 per cent; P = 0·034). Intermediate-risk patients randomized to the imaging and observation groups had the same proportion of negative appendicectomies (6·4 versus 6·7 per cent respectively; P = 0·884), number of admissions, number of perforations and length of hospital stay, but routine imaging was associated with an increased proportion of patients treated for appendicitis (53·4 versus 46·3 per cent; P = 0·020). CONCLUSION: AIR score-based risk classification can safely reduce the use of diagnostic imaging and hospital admissions in patients with suspicion of appendicitis. Registration number: NCT00971438 ( http://www.clinicaltrials.gov).

Relationship between tumour size and outcome in pancreatic ductal adenocarcinoma.

BACKGROUND: The size of pancreatic ductal adenocarcinoma (PDAC) at diagnosis is an indicator of outcome. Previous studies have focused mostly on patients with resectable disease. The aim of this study was to investigate the relationship between tumour size and risk of metastasis and death in a large PDAC cohort, including all stages. METHODS: Patients diagnosed with PDAC between 1988 and 2013 were identified from the Surveillance, Epidemiology, and End Results (SEER) database. Tumour size was defined as the maximum dimension of the tumour as provided by the registry. Metastatic spread was assessed, and survival was calculated according to size of the primary tumour using the Kaplan-Meier method. Cox proportional regression modelling was used to adjust for known confounders. RESULTS: Some 58 728 patients were included. There were 187 patients (0·3 per cent) with a tumour size of 0·5 cm or less, in whom the rate of distant metastasis was 30·6 per cent. The probability of tumour dissemination was associated with tumour size at the time of diagnosis. The association between survival and tumour size was linear for patients with localized tumours, but stochastic in patients with regional and distant stages. In patients with resected tumours, increasing tumour size was associated with worse tumour-specific survival, whereas size was not associated with survival in patients with unresected tumours. In the adjusted Cox regression analysis, the death rate increased by 4·1 per cent for each additional 1-cm increase in tumour size. CONCLUSION: Pancreatic cancer has a high metastatic capacity even in small tumours. The prognostic impact of tumour size is restricted to patients with localized disease.

Respiratory viral infections are underdiagnosed in patients with suspected sepsis.

The study aim was to investigate the prevalence and clinical relevance of viral findings by multiplex PCR from the nasopharynx of clinically septic patients during a winter season. During 11 weeks of the influenza epidemic period in January-March 2012, consecutive adult patients suspected to be septic (n = 432) were analyzed with cultures from blood and nasopharynx plus multiplex PCR for respiratory viruses on the nasopharyngeal specimen. The results were compared with those from microbiology analyses ordered as part of standard care. During the winter season, viral respiratory pathogens, mainly influenza A virus, human metapneumovirus, coronavirus, and respiratory syncytial virus were clinically underdiagnosed in 70% of patients positive by the multiplex PCR assay. During the first four weeks of the influenza epidemic, few tests for influenza were ordered by clinicians, indicating low awareness that the epidemic had started. Nasopharyngeal findings of Streptococcus pneumoniae and Haemophilus influenzae by culture correlated to pneumonia diagnosis, and in those patients laboratory signs of viral co-infections were common but rarely suspected by clinicians. The role of respiratory viral infections in patients presenting with a clinical picture of sepsis is underestimated. Specific antiviral treatment might be beneficial in some cases and may reduce spread in a hospital setting. Diagnosing viral infections may promote reduction of unnecessary antibiotic use. It can also be a tool for decisions concerning patient logistics, in order to minimize exposure of susceptible patients and personnel.

Impact of a fast-track surgery programme for pancreaticoduodenectomy.

BACKGROUND: Fast-track (FT) programmes are multimodal, evidence-based approaches to optimize patient outcome after surgery. The aim of this study was to evaluate the safety, clinical outcome and patients' experience of a FT programme after pancreaticoduodenectomy (PD) in a high-volume institution in Sweden. METHODS: Consecutive patients undergoing PD were studied before and after implementation of the FT programme. FT changes included earlier mobilization, standardized removal of the nasogastric tube and drain, and earlier start of oral intake. Patient experience was evaluated with European Organization for Research and Treatment of Cancer QLQ-C30 and QLQ-PAN26 questionnaires 2 weeks before and 4 weeks after surgery. RESULTS: Between 2011 and 2014, 100 consecutive patients undergoing PD were studied, of whom 50 received standard care (controls), followed by 50 patients treated after implementation of the FT programme. The nasogastric tube was removed significantly earlier in the FT group, and these patients were able fully to tolerate fluids and solid food sooner after PD. Delayed gastric emptying was significantly reduced in the FT group (26 versus 48 per cent; P = 0.030). Overall morbidity remained unchanged and there were no deaths in either group. Postoperative length of hospital stay was reduced from 14 to 10 days and hospital costs were decreased significantly. Health-related quality-of-life questionnaires showed similar patterns of change, with no significant difference between groups before or after surgery. CONCLUSION: The FT programme after PD was safe. Delayed gastric emptying, hospital stay and hospital costs were all reduced significantly. Although patients were discharged 4 days earlier in the FT group, this did not influence health-related quality of life compared with standard care.

Short-term complications and long-term morbidity of laparoscopic and open appendicectomy in a national cohort.

BACKGROUND: Laparoscopic appendicectomy has been proposed as the standard for surgical treatment of acute appendicitis, based on controversial evidence. This study compared outcomes after open and laparoscopic appendicectomy in a national, population-based cohort. METHODS: All patients who underwent open or intended laparoscopic appendicectomy in Sweden between 1992 and 2008 were identified from the Swedish National Patient Register. The outcomes were analysed according to intention to treat with multivariable adjustment for confounding factors and survival analytical techniques where appropriate. RESULTS: A total of 169 896 patients underwent open (136 754) or intended laparoscopic (33 142) appendicectomy. The rate of intended laparoscopic appendicectomy increased from 3·8 per cent (425 of 11 175) in 1992 to 32·9 per cent (3066 of 9329) in 2008. Laparoscopy was used most frequently in middle-aged patients, women and patients with no co-morbidity. The rate of conversion from laparoscopy to open appendicectomy decreased from 75·3 per cent (320 of 425) in 1992 to 19·7 per cent (603 of 3066) in 2008. Conversion was more frequent in women and those with perforated appendicitis, and the rate increased with age and increasing co-morbidity. After adjustment for co-variables, compared with open appendicectomy, laparoscopy was associated with a shorter length of hospital stay (by 0·06 days), a lower frequency of negative appendicectomy (adjusted odds ratio (OR) 0·59; P < 0·001), wound infection (adjusted OR 0·54; P = 0·004) and wound rupture (adjusted OR 0·44; P = 0·010), but higher rates of intestinal injury (adjusted OR 1·32; P = 0·042), readmission (adjusted OR 1·10; P < 0·001), postoperative abdominal abscess (adjusted OR 1·58; P < 0·001) and urinary infection (adjusted OR 1·39; P = 0·020). Laparoscopy had a lower risk of postoperative small bowel obstruction during the first 2 years after surgery, but not thereafter. CONCLUSION: The outcomes of laparoscopic and open appendicectomy showed a complex and contrasting pattern and small differences of limited clinical importance. The choice of surgical method therefore depends on the local situation, the surgeon's experience and the patient's preference.

In vivo toxicity and biodistribution of intraperitoneal and intravenous poly-L-lysine and poly-L-lysine/poly-L-glutamate in rats.

The combination of two differently charged polypeptides, poly-L-lysine (PL) and poly-L-glutamate (PG), has shown excellent postsurgical antiadhesive properties. However, the high molecular, positively charged PL is toxic in high doses, proposed as lysis of red blood cells. This study aims to elucidate the in vivo toxicity and biodistribution of PL and complex bound PLPG comparing intravenous and intraperitoneal administration. Fifty-six Sprague-Dawley rats were used in a model with repeated blood samples within 30 min examining blood gases and blood smears. Similarly, FITC labelled PL were used to track bio distribution and clearance of PL, given as single dose and complex bound to PG after intravenous and intraperitoneal administration. Tissue for histology and immunohistochemistry was collected. Blood gases and blood smears as well as histology points to a toxic effect of high dose PL given intravenously but not after intraperitoneal administration. The toxic effect is exerted through endothelial disruption and subsequent bleeding in the lungs, provoking sanguineous lung edema. FITC-labelled PL experiments reveal a rapid clearance with differences between routes and complex binding. This study advocates a new theory of the toxic effects in vivo of high molecular PL. PLPG complex is safe to use as antiadhesive prevention based on this toxicity study given that PL is always intraperitoneally administered in combination with PG and that the dose is adequate.

Prevention of pleural adhesions by bioactive polypeptides - a pilot study.

OBJECTIVE: Postoperative pleural adhesions lead to major problems in repeated thoracic surgery. To date, no antiadhesive product has been proven clinically effective. Previous studies of differently charged polypeptides, poly-L-lysine (PL) and poly-L-glutamate (PG) have shown promising results reducing postoperative abdominal adhesions in experimental settings. This pilot study examined the possible pleural adhesion prevention by using the PL+PG concept after pleural surgery and its possible effect on key parameters; plasmin activator inhibitor-1 (PAI-1) and tissue growth factor beta 1 (TGFb) in the fibrinolytic process. METHODS: A total of 22 male rats were used in the study, one control group (n=10) and one experimental group (n=12). All animals underwent primary pleural surgery, the controls receiving saline in the pleural cavity and the experimental group the PL+PG solution administered by spray. The animals were evaluated on day 7. Macroscopic appearance of adhesions was evaluated by a scoring system. Histology slides of the adhesions and pleural biopsies for evaluation of PAI-1 and TGFb1 were taken on day 7. RESULTS: A significant reduction of adhesions in the PL+PG group (p<0.05) was noted at day 7 both regarding the length and severity of adhesions. There were no significant differences in the concentration of PAI-1 and TGFb1 when comparing the two groups. CONCLUSIONS: PL+PG may be used to prevent pleural adhesions. The process of fibrinolysis, and fibrosis was though not affected after PLPG administration.

Cellulose nanofibers (CNFs) in the recycling of nickel and cadmium battery metals using electrodeposition.

Cellulose nanofibers (CNFs) were employed in the aqueous electrodeposition of nickel and cadmium for battery metal recycling. The electrowinning of mixed Ni-Cd metal ion recycling solutions demonstrated that cadmium with a purity of over 99% could be selectively extracted while leaving the nickel in the solution. Two types of CNFs were evaluated: negatively charged CNFs (a-CNF) obtained through acid hydrolysis (-75 µeq. g-1) and positively charged CNFs (q-CNF) functionalized with quaternary ammonium groups (+85 µeq. g-1). The inclusion of CNFs in the Ni-Cd electrolytes induced growth of cm-sized dendrites in conditions where dendrites were otherwise not observed, or increased the degree of dendritic growth when it was already present to a lesser extent. The augmented dendritic growth correlated with an increase in deposition yields of up to 30%. Additionally, it facilitated the formation of easily detachable dendritic structures, enabling more efficient processing on a large scale and enhancing the recovery of the toxic cadmium metal. Regardless of the charged nature of the CNFs, both negatively and positively charged CNFs led to a significant formation of protruding cadmium dendrites. When deposited separately, dendritic growth and increased deposition yields remained consistent for the cadmium metal. However, dendrites were not observed during the deposition of nickel; instead, uniformly deposited layers were formed, albeit at lower yields (20%), when positively charged CNFs were present. This paper explores the potential of utilizing cellulose and its derivatives as the world's largest biomass resource to enhance battery metal recycling processes.

Thrombospondin-2 as a diagnostic biomarker for distal cholangiocarcinoma and pancreatic ductal adenocarcinoma.

PURPOSE: Distal cholangiocarcinoma and pancreatic ductal adenocarcinoma are malignancies with poor prognoses that can be difficult to distinguish preoperatively. Thrombospondin-2 has been proposed as a novel diagnostic biomarker for early pancreatic ductal adenocarcinoma. The aim of the present study was to evaluate thrombospondin-2 as a diagnostic and prognostic biomarker in combination with current biomarker CA 19-9 for distal cholangiocarcinoma and pancreatic ductal adenocarcinoma. METHODS: Thrombospondin-2 was measured in prospectively collected serum samples from patients who underwent surgery with a histopathological diagnosis of distal cholangiocarcinoma (N = 51), pancreatic ductal adenocarcinoma (N = 52) and benign pancreatic diseases (N = 27) as well as healthy blood donors (N = 52) using an enzyme-linked immunosorbent assay. RESULTS: Thrombospondin-2 levels (ng/ml) were similar in distal cholangiocarcinoma 55 (41-77) and pancreatic ductal adenocarcinoma 48 (35-80) (P = 0.221). Thrombospondin-2 + CA 19-9 had an area under the curve of 0.92 (95% CI 0.88-0.97) in differentiating distal cholangiocarcinoma and pancreatic ductal adenocarcinoma from healthy donors which was superior to CA 19-9 alone (P < 0.001). The diagnostic value of adding thrombospondin-2 to CA 19-9 was larger in early disease stages. Thrombospondin-2 did not provide additional value to CA 19-9 in differentiating the benign disease group; however, heterogeneity was notable in the benign cohort. Three of five patients with autoimmune pancreatitis patients had greatly elevated thrombospondin-2 levels. Thrombospondin-2 levels had no correlation with prognoses. CONCLUSIONS: Serum thrombospondin-2 in combination with CA 19-9 has potential as a biomarker for distal cholangiocarcinoma and pancreatic cancer.

Systematic review of immunohistochemical biomarkers to identify prognostic subgroups of patients with pancreatic cancer.

BACKGROUND: Pancreatic ductal adenocarcinoma (PDAC) carries a dismal prognosis. There is a need to identify prognostic subtypes of PDAC to predict clinical and therapeutic outcomes accurately, and define novel therapeutic targets. The purpose of this review was to provide a systematic summary and review of available data on immunohistochemical (IHC) prognostic and predictive markers in patients with PDAC. METHODS: Relevant articles in English published between January 1990 and June 2010 were obtained from PubMed searches. Other articles identified from cross-checking references and additional sources were reviewed. The inclusion was limited to studies evaluating IHC markers in a multivariable setting. RESULTS: Database searches identified 76 independent prognostic and predictive molecular markers implicated in pancreatic tumour growth, apoptosis, angiogenesis, invasion and resistance to chemotherapy. Of these, 11 markers (Ki-67, p27, p53, transforming growth factor ß1, Bcl-2, survivin, vascular endothelial growth factor, cyclo-oxygenase 2, CD34, S100A4 and human equilibrative nucleoside transporter 1) provided independent prognostic or predictive information in two or more separate studies. CONCLUSION: None of the molecular markers described can be recommended for routine clinical use as they were identified in small cohorts and there were inconsistencies between studies. Their prognostic and predictive values need to be validated further in prospective multicentre studies in larger patient populations. A panel of molecular markers may become useful in predicting individual patient outcome and directing novel types of intervention.

Survival and prognostic factors in patients with small bowel carcinoid tumour.

BACKGROUND: Previous studies of small bowel carcinoid tumours usually presented overall or relative survival. This study, in addition, evaluated disease-specific survival in a cohort of patients in a geographically defined population. METHODS: Patients diagnosed with carcinoid of the jejunum or ileum in Jönköping County between 1960 and 2005 were eligible for inclusion. Available tumour specimens were re-examined to confirm the diagnosis. Medical records and pathology reports were reviewed in detail. RESULTS: A total of 145 patients were included in the study. One hundred and thirty-five patients underwent surgery in connection with the diagnosis. Resection was considered complete (R0) in 74 patients (54·8 per cent). Only two localized tumours recurred, whereas no patient with distant metastases was cured. Patients with regional metastases who underwent R0 resection had a better survival than patients with incomplete resection (P = 0·005), and a majority of patients remained recurrence-free. Median overall survival was 7·2 years and median disease-specific survival 12·3 years. In multivariable analysis, age 61-74 years (hazard ratio (HR) 3·78, 95 per cent confidence interval 1·86 to 7·68), age 75 years or more (HR 3·96, 1·79 to 8·74), distant metastases (HR 14·44, 1·59 to 131·36) and incomplete tumour resection (HR 2·71, 1·11 to 6·61) were associated with worse disease-specific survival. Later time period of diagnosis (HR 0·45, 0·24 to 0·84) was associated with better disease-specific survival. CONCLUSION: Age, disease stage and complete resection were identified as independent prognostic factors for survival in patients with small bowel carcinoid tumours. The importance of achieving R0 resection is therefore emphasized.

Warfarin therapy and incidence of cerebrovascular complications in left-sided native valve endocarditis.

Anticoagulant therapy has been anticipated to increase the risk of cerebrovascular complications (CVC) in native valve endocarditis (NVE). This study investigates the relationship between ongoing oral anticoagulant therapy and the incidence of symptomatic CVC in left-sided NVE. In a prospective cohort study, the CVC incidence was compared between NVE patients with and without ongoing warfarin. Among 587 NVE episodes, 48 (8%) occurred in patients on warfarin. A symptomatic CVC was seen in 144 (25%) patients, with only three on warfarin. CVC were significantly less frequent in patients on warfarin (6% vs. 26%, odds ratio [OR] 0.20, 95% confidence interval [CI] 0.06-0.6, p = 0.006). No increase in haemorrhagic lesions was detected in patients on warfarin. Staphylococcus aureus aetiology (adjusted OR [aOR] 6.3, 95% CI 3.8-10.4) and vegetation length (aOR 1.04, 96% CI 1.01-1.07) were risk factors for CVC, while warfarin on admission (aOR 0.26, 95% CI 0.07-0.94), history of congestive heart failure (adjusted OR 0.22, 95% CI 0.1-0.52) and previous endocarditis (aOR 0.1, 95% CI 0.01-0.79) correlated with lower CVC frequency.

Suicide mortality trends in young people aged 15 to 19 years in Lithuania.

AIM: This paper considers the suicide mortality trends from 1990-2009 in young people aged 15 to 19 years in Lithuania. METHODS: Suicide and injury mortality data, plus mortality data from all causes, were used to compare the trend lines. RESULTS: Suicide mortality rate in young people aged 15-19 years and in all population showed a rising trend from 1990, and then a decreasing trend from 2002 year. This trend was significant exclusively in boys. When comparing suicide deaths as a percentage of injury deaths and of all deaths in the age group 15-19 years, rising trends for boys were evident, whilst in girls, there was no evidence of change. CONCLUSIONS: In Lithuania, from early 1990s, the frequency of suicide increased amongst adults and young people aged 15-19 years. After 2002, a decrease in deaths by suicide was observed both for the whole population and for young people aged 15-19 years. The rise and fall was obvious for boys. The reasons for different trends may have been influenced by the political and socioeconomic instability in the 1990-2002 period, and the socioeconomic stability, together with active preventive measures, from 2002. Although the consumption of modern Selective serotonin reuptake inhibitors (SSRIs) increased during the same time, suicide mortality was again high during the economic crisis in 2008-2009.

Surgical Infections and Antibiotic Stewardship: In Need for New Directions.

BACKGROUND AND AIMS: Patients undergoing surgery are prone to infections, either at the site of surgery (superficial or organ-space) or at remote sites (e.g. pneumonia or urinary tract). Surgical site infections are associated with substantial morbidity and mortality, increased length of hospital stay and represent a huge burden to the health economy across all healthcare systems. Here we discuss recent advances and challenges in the field of surgical site infections. MATERIAL AND METHODS: Review of pertinent English language literature. RESULTS: Numerous guidelines and recommendations have been published in order to prevent surgical site infections. Compliance with these evidence-based guidelines vary and has not resulted in any major decrease in the surgical site infection rate. To date, most efforts to reduce surgical site infection have focused on the role of the surgeon, but a more comprehensive approach is necessary. CONCLUSION: Surgical site infections need to be addressed in a structured way, including checklists, audits, monitoring, and measurements. All stakeholders, including the medical profession, the society, and the patient, need to work together to reduce surgical site infections. Most surgical site infections are preventable-and we need a paradigm shift to tackle the problem.

Experimental review of PEI electrodeposition onto copper substrates for insulation of complex geometries.

Polyetherimide (PEI) was used for coating copper substrates via electrophoretic deposition (EPD) for electrical insulation. Different substrate preparation and electrical field application techniques were compared, demonstrating that the use of a pulsed voltage of 20 V allowed for the best formation of insulating coatings in the 2-6 µm thickness range. The results indicate that pulsed EPD is the best technique to effectively coat conductive substrates with superior surface finish coatings that could pass a dielectric withstand test at 10 kV mm-1, which is of importance within the EV automotive industry.

Induction of specific immune unresponsiveness using purified mixed leukocyte culture-activated T lymphoblasts as autoimmunogen. I. Demonstration of general validity as to species and histocompatibility barriers.

Normal immunocompetent T lymphocytes can be induced into specific proliferation if confronted with the relevant alloantigen in vitro. Such mixed leuko-cyteculture-activated T lymphoblasts carring idiotypic receptors on their surface can be purified using velocity sedimentation and serve as immunogen if administered in adjuvant to the autologous host. Autoblast immunization can be shown to lead to specific, long-lasting unresponsiveness against the relevant alloantigens, while leaving reactivity against third-party antigens intact. When tested as to general validity, it could be shown to function in all species analyzed (mouse, rat, and guinea pig) as well as across both major and minor histocompatibility barriers. No negative side effects have been noted so far. It would thus seem clear that autoblast immunization using the above described scheme may serve as a general tool in inducing long-lasting, specific unresponsiveness in any species and across any histocompatibility barrier.

Induction of specific immune unresponsiveness with purified mixed leukocyte culture-activated T lymphoblasts as autoimmunogen. II. An analysis of the effects measured at the cellular and serological levels.

T lymphoblasts specific for foreign histocompatibility antigens and purified via mixed leukocyte culture (MLC) and 1 g velocity sedimentation procedures can be used as autoimmunogen to produce specific immunological unresponsiveness in adult animals. This unresponsiveness is positively correlated to the production of autoanti-idiotypic antibodies in the blast immunized animals and no evidence of coexisting alloimmunity was found. We consider this autoanti-idiotypic immunity to be the specific inducing agent of the immune tolerance. The blast immunization procedure will lead to selective reduction in T-cell reactivity against the relevant alloantigens as measured by MLC, cell-mediated lympholysis, or graft-versus-host assays. However, in individual animals, dichtomy in suppression between two T-cell assays could sometimes be observed indicating elimination of only a select group of idiotypic functionally distinct population of T cells in these blast-immunized animals. Attempts to abrogate already immune animals by the autoblast procedure were successful, in part suggesting the use of the present procedure when trying to induce in accelerated reversion of such immunity.