The impact of COVID-19 on surgical training: a systematic review.

BACKGROUND: Coronavirus disease (COVID-19) has caused global disruption to health care. Non-urgent elective surgical cases have been cancelled, outpatient clinics have reduced and there has been a reduction in the number of patients presenting as an emergency. These factors will drastically affect the training opportunities of surgical trainees. The aim of this systematic review is to describe the impact of COVID-19 on surgical training globally. METHODS: The review was performed in line with Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and registered with the Open Science Framework (OSF). Medline, EMBASE, PubMed and the Cochrane Central Register of Controlled Trials were searched. RESULTS: The searches identified 499 articles, 29 of which were included in the review. This contained data from more than 20 countries with 5260 trainees and 339 programme directors. Redeployment to non-surgical roles varied across studies from 6% to 35.1%. According to all of the studies, operative experience has been reduced. Knowledge learning had been switched to online platforms across 17 of the studies and 7 reported trainees had increased time to devote to educational/academic activities. All of the studies reporting on mental health report negative associations with increased stress, ranging from 54.9% to 91.6% of trainees. CONCLUSIONS: The impact of COVID-19 on surgical trainees has been experienced globally and across all specialities. Negative effects are not limited to operative and clinical experience, but also the mental health and wellbeing of trainees. Delivery of surgical training will need to move away from traditional models of learning to ensure trainees are competent and well supported.

Effect of publishing surgeon-specific outcomes on surgical training.

BACKGROUND: Over the past 10 years, the National Health Service in England has started to publish surgeon-specific outcomes publicly. The aim of this study was to investigate how this has affected training case exposure for surgeons in training. METHODS: Anonymized data were collected from the Intercollegiate Surgical Curriculum Programme database for operations in each specialty with published surgeon outcomes, involving surgical trainees on an approved training programme between 1 January 2011 and 31 December 2016. Trainee and supervisor involvement in operations before and after the start of publication of surgeon-specific outcomes were compared using mixed-effects models. RESULTS: A total of 163 076 recorded operative procedures were included. A statistically significant improvement in exposure to training procedures was observed for anterior resection of rectum, carotid endarterectomy, gastrectomy, meningioma excision, prostatectomy and thyroidectomy following the introduction of publication of surgeon outcomes. In coronary artery bypass grafting (CABG) and total hip replacement (THR), however, there was a reduction in involvement in training procedures. This was apparent for both trainee and supervisor involvement in CABG, and for trainee involvement in THR. CONCLUSION: Exposure to training procedures has improved rather than declined in the UK in the majority of surgical specialties, since the publication of surgeon-specific outcomes.

Expression of growth mediators in the gingival crevicular fluid of patients with aggressive periodontitis undergoing periodontal surgery.

OBJECTIVES: To describe changes in growth factor mediators in the gingival crevicular fluid (GCF) of patients with aggressive periodontitis (AgP) undergoing regenerative (GTR) and access flap (AF) surgery. MATERIALS AND METHODS: This was a 12-month, single-blind, split-mouth RCT involving 18 AgP patients with a bilateral intrabony defect which was treated with GTR or AF. GCF was collected prior to surgery and at subsequent follow-up visits from 3 days to 12 months post-operatively, and the levels of angiopoietin-1 (Ang-1), vascular-endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), bone morphogenetic protein-2 (BMP-2), osteoprotegerin (OPG), tissue inhibitor of metalloproteinase 1 (TIMP-1), keratinocyte growth factor (KGF) and platelet-derived growth factor-AB (PDGF-AB) were measured. At baseline, 6 and 12 months post-surgery, periodontal clinical parameters were evaluated. ANOVA was applied to test for differences in the amount of mediators (p < 0.05). RESULTS: Higher amounts of BMP-2 and OPG and a higher area under the curve (AUC) of KGF at the GTR versus AF sites were observed. The maximum change in the amount of KGF correlated significantly with periodontal clinical parameters at the GTR sites at 6 and 12 months. The AUC over 30 days of the amount of Ang-1, VEGF and KGF significantly correlated with periodontal clinical parameters at the AF sites at 6 months. CONCLUSIONS: AF and GTR differentially affected the profile of the growth mediators in GCF, and significant correlations between certain GCF mediators and periodontal clinical outcomes were identified. CLINICAL RELEVANCE: GCF components represent attractive prognostic markers for periodontal tissues undergoing repair or regeneration. However, the available evidence is not robust enough to suggest the use of a specific marker, and future adequately powered studies are warranted to identify the most relevant mediators that could be applied in clinical practice.

Long-term results and recurrence patterns from SCALOP: a phase II randomised trial of gemcitabine- or capecitabine-based chemoradiation for locally advanced pancreatic cancer.

BACKGROUND: SCALOP, a randomised, phase II trial, tested the activity and safety of gemcitabine (GEM)-based and capecitabine (CAP)-based chemoradiation (CRT) for locally advanced pancreatic cancer (LAPC). Here we present the long-term outcomes. METHODS: Eligibility: histologically proven LAPC ⩽7 cm. Following 12 weeks of induction GEMCAP chemotherapy (three cycles: GEM 1000 mg m-2 days 1, 8, 15; CAP 830 mg m-2 days 1-21 q28 days) patients with stable/responding disease, tumour ⩽6 cm, and WHO Performance Status 0-1 were randomised to receive one cycle GEMCAP followed by CAP (830 mg m-2 b.d. on weekdays only) or GEM (300 mg m-2 weekly) with radiation (50.4 Gy per 28 fractions). RESULTS: One-hundred fourteen patients (28 UK centres) were registered between 24 December 2009 and 25 October 2011, and 74 were randomised (CAP-RT=36; GEM-RT=38). At the time of this analysis, 105 of the 114 patients had died and the surviving 9 patients had been followed up for a median of 10.9 months (IQR: 2.9-18.7). Updated median OS was 17.6 months (95% CI: 14.6-22.7) in the CAP-CRT arm and 14.6 months (95% CI: 11.1-16.0) in the GEM-CRT arm (intention-to-treat adjusted hazard ratio (HR): 0.68 (95% CI: 0.38-1.21, P=0.185)); median progression-free survival (PFS) was 12.0 months (95% CI: 10.0-15.2) in the CAP-CRT arm and 10.4 months (95% CI: 8.8-12.7) in the GEM-CRT arm (intention-to-treat adjusted HR: 0.60 (95% CI: 0.32-1.14, P=0.120)). In baseline multivariable model, age ⩾65 years, better performance status, CA19.9<613 IU l-1, and shorter tumour diameter predicted improved OS. CAP-CRT, age ⩾65 years, better performance status, CA19.9 <46 IU ml-1 predicted improved OS and PFS in the pre-radiotherapy model. Nine-month PFS was highly predictive of OS. CONCLUSIONS: CAP-CRT remains the superior regimen. SCALOP showed that patients with CA19.9 <46 IU ml-1 after induction chemotherapy are more likely to benefit from CRT.

Long-term results and recurrence patterns from SCOPE-1: a phase II/III randomised trial of definitive chemoradiotherapy +/- cetuximab in oesophageal cancer.

BACKGROUND: The SCOPE-1 study tested the role of adding cetuximab to conventional definitive chemoradiotherapy (dCRT), and demonstrated greater toxicity and worse survival outcomes. We present the long-term outcomes and patterns of recurrence. METHODS: SCOPE-1 was a phase II/III trial in which patients were randomised to cisplatin 60 mg m-2 (day 1) and capecitabine 625 mg m-2 bd (days 1-21) for four cycles +/- cetuximab 400 mg m-2 day 1 then by 250 mg m-2 weekly. Radiotherapy consisted of 50 Gy/25# given concurrently with cycles 3 and 4. Recruitment was between February 2008 and February 2012, when the IDMC recommended closure on the basis of futility. RESULTS: About 258 patients (dCRT=129; dCRT+cetuximab (dCRT+C)=129) were recruited from 36 centres. About 72.9% (n=188) had squamous cell histology. The median follow-up (IQR) was 46.2 (35.9-48.3) months for surviving patients. The median overall survival (OS; months; 95% CI) was 34.5 (24.7-42.3) in dCRT and 24.7 (18.6-31.3) in dCRT+C (hazard ratio (HR)=1.25, 95% CIs: 0.93-1.69, P=0.137). Median progression-free survival (PFS; months; 95% CI) was 24.1 (15.3-29.9) and 15.9 (10.7-20.8) months, respectively (HR=1.28, 95% CIs: 0.94-1.75; P=0.114). On multivariable analysis only earlier stage, full-dose RT, and higher cisplatin dose intensity were associated with improved OS. CONCLUSIONS: The mature analysis demonstrates that the dCRT regimen used in the study provided useful survival outcomes despite its use in patients who were largely unfit for surgery or who had inoperable disease. Given the competing risk of systemic and local failure, future studies should continue to focus on enhancing local control as well as optimising systemic therapy.

Meta-analysis of operative experiences of general surgery trainees during training.

BACKGROUND: General surgical training curricula around the world set defined operative numbers to be achieved before completion of training. However, there are few studies reporting total operative experience in training. This systematic review aimed to quantify the published global operative experience at completion of training in general surgery. METHODS: Electronic databases were searched systematically for articles in any language relating to operative experience in trainees completing postgraduate general surgical training. Two reviewers independently assessed citations for inclusion using agreed criteria. Studies were assessed for quantitative data in addition to study design and purpose. A meta-analysis was performed using a random-effects model of studies with appropriate data. RESULTS: The search resulted in 1979 titles for review. Of these, 24 studies were eligible for inclusion in the review and data from five studies were used in the meta-analysis. Studies with published data of operative experience at completion of surgical training originated from the USA (19), UK (2), the Netherlands (1), Spain (1) and Thailand (1). Mean total operative experience in training varied from 783 procedures in Thailand to 1915 in the UK. Meta-analysis produced a mean pooled estimate of 1366 (95 per cent c.i. 1026 to 1707) procedures per trainee at completion of training. There was marked heterogeneity between studies (I2 = 99·6 per cent). CONCLUSION: There is a lack of robust data describing the operative experiences of general surgical trainees outside the USA. The number of surgical procedures performed by general surgeons in training varies considerably across the world.

Patient-reported outcomes during and after definitive chemoradiotherapy for oesophageal cancer.

BACKGROUND: Limited data describe patient-reported outcomes (PROs) of localised oesophageal cancer treated with definitive chemoradiotherapy(CRT). The phase 2/3 SCOPE-1 trial assessed the effectiveness of CRT±cetuximab. The trial for the first time provided an opportunity to describe PROs from a multi-centre group of patients treated with CRT that are presented here. METHODS: Patients undergoing CRT±cetuximab within the SCOPE-1 trial (258 patients from 36 UK centres) completed generic-, disease- and treatment-specific health-related quality of life (HRQL) questionnaires (EORTC QLQ-C30, QLQ-OES18, Dermatology Life-Quality Index (DLQI)) at baseline and at 7, 13, 24, 52 and 104 weeks. Mean EORTC functional scale scores (>15 point change significant), DLQI scores (>4 point change significant) and proportions of patients (>15% significant) with 'minimal' or 'severe' symptoms are presented. RESULTS: Questionnaire response rates were good. At baseline, EORTC functional scores were high (>75%) and few symptoms were reported except for severe problems with fatigue, insomnia and eating-related symptoms (e.g., appetite loss, dysphagia, dry mouth) in both groups(>15%). Functional aspects of health deteriorated and symptoms increased with treatment and by week 13 global quality of life, physical, role and social function significantly deteriorated and more problems with fatigue, dyspnoea, appetite loss and trouble with taste were reported. Recovery occurred by 6 months (except severe fatigue and insomnia in >15% of patients) and maintained at follow-up with no differences between groups. CONCLUSIONS: CRT for localised oesophageal cancer has a significant detrimental impact on many aspects of HRQL; however, recovery is achieved by 6 months and maintained with the exception of persisting problems with severe fatigue and insomnia. The data suggest that the HRQL recovery after definitive CRT is quicker, and there is little lasting deficit compared with treatment including surgery. These data need to be compared with HRQL data from studies evaluating treatments including surgery for oesophageal cancer.

Physical and textural properties of functional edible protein films from soybean using an innovative 3D printing technology.

Increasing market demand for sustainable, environmentally friendly edible film materials has called for the development of new customizable production methods utilizing emerging technologies such as 3D printing. We hereby report a new method to generate functional edible soy protein isolate films prepared from three types of soybeans (AR-R11-7999, MO-S17-17168, and MO-S17-19874R) using an innovative 3D printing technology. The protein contents in AR-R11-7999, MO-S17-17168, and MO-S17-19874R soybean meals and their corresponding protein isolates were 40.0, 39.1, and 39.9; and 84.5, 84.7, and 87.3 % (w/w, dry basis), respectively. Response surface methodology was used to maximize the tensile and puncture strength and minimize the thickness of the 3D-printed edible films using protein concentration, plasticizer concentration (glycerol), and drying time as the independent variables. The optimized film production conditions were determined as soy protein concentration: 8.91%, plasticizer concentration: 3.00%, and drying time: 3.98 h with a desirability value of 0.7428. The optimized conditions were then successfully verified with the original soybean lot with a nonsignificant difference in physical properties. At the optimized conditions, the 3D-printed edible films using three soybean lots revealed: 0.108-0.114 mm thickness; 14.79-16.07 MPa tensile strength; 6.97-8.20 N puncture strength; 90.81-91.53, -1.89 to -1.31, and 14.85-17.25 were color parameters L*, a*, and b*, respectively; 1.22-1.36 g/cm3 density; and 104.4-105.7% elongation at break ratio (%). PRACTICAL APPLICATION: Edible soy protein films produced by an extrusion-based 3D printing approach are highly customizable and precise, and could be produced at an industrial scale. This newly produced environment-friendly soy protein-based edible film can serve as an alternate packaging to synthetic plastics and reduce the environmental landfill problem while adding value to soybean produced in the mid-south United States.

R-Ras interacts with filamin a to maintain endothelial barrier function.

The molecular mechanisms regulating vascular barrier integrity remain incompletely elucidated. We have previously reported an association between the GTPase R-Ras and repeat 3 of Filamin A (FLNa). Loss of FLNa has been linked to increased vascular permeability. We sought to determine whether FLNa's association with R-Ras affects endothelial barrier function. We report that in endothelial cells endogenous R-Ras interacts with endogenous FLNa as determined by co-immunoprecipitations and pulldowns with the FLNa-GST fusion protein repeats 1-10. Deletion of FLNa repeat 3 (FLNaΔ3) abrogated this interaction. In these cells FLNa and R-Ras co-localize at the plasma membrane. Knockdown of R-Ras and/or FLNa by siRNA promotes vascular permeability, as determined by TransEndothelial Electrical Resistance and FITC-dextran transwell assays. Re-expression of FLNa restored endothelial barrier function in cells lacking FLNa whereas re-expression of FLNaΔ3 did not. Immunostaining for VE-Cadherin in cells with knocked down R-Ras and FLNa demonstrated a disorganization of VE-Cadherin at adherens junctions. Loss of R-Ras and FLNa or blocking R-Ras function via GGTI-2133, a selective R-Ras inhibitor, induced vascular permeability and increased phosphorylation of VE-Cadherin (Y731) and Src (Y416). Expression of dominant negative R-Ras promoted vascular permeability that was blocked by the Src inhibitor PP2. These findings demonstrate that maintaining endothelial barrier function is dependent upon active R-Ras and association between R-Ras and FLNa and that loss of this interaction promotes VE-Cadherin phosphorylation and changes in downstream effectors that lead to endothelial leakiness.

Degranulation plays an essential part in regulating cell surface expression of Fas ligand in T cells and natural killer cells.

Fas ligand (FasL) triggers apoptosis during cytotoxicity mediated by cytotoxic T lymphocytes and during immune downregulation. The ability of T cells and natural killer cells to trigger apoptosis through this mechanism is controlled by the cell surface expression of FasL (ref. 2). Because FasL expression is up-regulated on activation, FasL was thought to be delivered directly to the cell surface. Here we show that newly synthesized FasL is stored in specialized secretory lysosomes in both CD4+ and CD8+ T cells and natural killer cells, and that polarized degranulation controls the delivery of FasL to the cell surface. In this way, FasL-mediated apoptosis is finely controlled by receptor-mediated target-cell recognition. The cytoplasmic tail of FasL contains signals that sort FasL to secretory lysosomes in hemopoietic cells. This pathway may provide a general mechanism for controlling the cell surface appearance of proteins involved in immune regulation.

The quantitative impact of COVID-19 on surgical training in the United Kingdom.

BACKGROUND: COVID-19 has had a global impact on all aspects of healthcare including surgical training. This study aimed to quantify the impact of COVID-19 on operative case numbers recorded by surgeons in training, and annual review of competency progression (ARCP) outcomes in the UK. METHODS: Anonymized operative logbook numbers were collated from electronic logbook and ARCP outcome data from the Intercollegiate Surgical Curriculum Programme database for trainees in the 10 surgical specialty training specialties.Operative logbook numbers and awarded ARCP outcomes were compared between predefined dates. Effect sizes are reported as incident rate ratios (IRR) with 95 per cent confidence intervals. RESULTS: Some 5599 surgical trainees in 2019, and 5310 in surgical specialty training in 2020 were included. The IRR was reduced across all specialties as a result of the COVID-19 pandemic (0.62; 95 per cent c.i. 0.60 to 0.64). Elective surgery (0.53; 95 per cent c.i. 0.50 to 0.56) was affected more than emergency surgery (0.85; 95 per cent c.i. 0.84 to 0.87). Regional variation indicating reduced operative activity was demonstrated across all specialties. More than 1 in 8 trainees in the final year of training have had their training extended and more than a quarter of trainees entering their final year of training are behind their expected training trajectory. CONCLUSION: The COVID-19 pandemic has had a major effect on surgical training in the UK. Urgent, coordinated action is required to minimize the impacts from the reduction in training in 2020.

Differential endocytosis of CD4 in lymphocytic and nonlymphocytic cells.

The endocytosis of the T cell differentiation antigen CD4 has been investigated in CD4-transfected HeLa cells, the promyelocytic HL-60 cell line, and in a number of leukemia- or lymphoma-derived T cell lines. CD4 internalization was followed using radioiodinated antibodies in an acid-elution endocytosis assay, or by covalently modifying cell surface proteins with biotin and analyzing CD4 distributions by immunoprecipitation; both approaches gave equivalent results. The assays demonstrated that in transfected HeLa cells and in HL-60 cells CD4 was constitutively internalized and recycled in the absence of ligand. Immunogold labeling and electron microscopy demonstrated that CD4 enters cells through coated pits. In contrast to the nonlymphocytic cells, T cell lines showed very little endocytosis of CD4. Measurements of fluid phase endocytosis and morphometric analysis of the endosome compartment indicated that the endocytic capacities of HeLa and lymphoid cells are equivalent and suggested that the low level of CD4 uptake in lymphocytic cells is due to exclusion of CD4 from coated pits. This conclusion was supported by experiments using truncated CD4 molecules, lacking the bulk of the cytoplasmic domain, which were internalized equally efficiently in both transfected lymphocytes and HeLa cells. Together, these results indicate that the cytoplasmic domain of CD4 mediates the different interactions with the endocytic apparatus in lymphoid and nonlymphoid cells. We suggest that the CD4-associated lymphocyte-specific protein tyrosine kinase p56lck may be involved in preventing CD4 endocytosis in T cells.

Comparison of different methods for thin section EM analysis of Mycobacterium smegmatis.

Bacteria are generally difficult specimens to prepare for conventional resin section electron microscopy and mycobacteria, with their thick and complex cell envelope layers being especially prone to artefacts. Here we made a systematic comparison of different methods for preparing Mycobacterium smegmatis for thin section electron microscopy analysis. These methods were: (1) conventional preparation by fixatives and epoxy resins at ambient temperature. (2) Tokuyasu cryo-section of chemically fixed bacteria. (3) rapid freezing followed by freeze substitution and embedding in epoxy resin at room temperature or (4) combined with Lowicryl HM20 embedding and ultraviolet (UV) polymerization at low temperature and (5) CEMOVIS, or cryo electron microscopy of vitreous sections. The best preservation of bacteria was obtained with the cryo electron microscopy of vitreous sections method, as expected, especially with respect to the preservation of the cell envelope and lipid bodies. By comparison with cryo electron microscopy of vitreous sections both the conventional and Tokuyasu methods produced different, undesirable artefacts. The two different types of freeze-substitution protocols showed variable preservation of the cell envelope but gave acceptable preservation of the cytoplasm, but not lipid bodies, and bacterial DNA. In conclusion although cryo electron microscopy of vitreous sections must be considered the 'gold standard' among sectioning methods for electron microscopy, because it avoids solvents and stains, the use of optimally prepared freeze substitution also offers some advantages for ultrastructural analysis of bacteria.

Association between periodontitis and common variants in the promoter of the interleukin-6 gene.

We recently reported an association between interleukin-6 (IL6) polymorphisms (SNPs) and haplotypes and aggressive periodontitis (AgP). The aim of this study was to investigate this association in a larger cohort of subjects, affected by either aggressive or chronic periodontitis. Five IL6 SNPs were analyzed in 765 subjects (167 generalized aggressive periodontitis, 57 localized aggressive, 310 chronic periodontitis and 231 periodontally healthy). Among Caucasians (n=454) there were moderate associations for -1363T allele (p=0.011) and for -174GG and -1363GG genotypes with diagnosis of periodontitis (respectively, p=0.044, OR=1.6, 95% CI=1.0-2.4, and p=0.017, OR=1.8, 95% CI=1.1-2.8, adjusted for age, gender and smoking). Haplotypes containing the -174G>C, -1363G>T and -1480C>G polymorphisms were associated with diagnosis of periodontitis (p=0.02). Subgroup analysis by disease phenotype showed associations for the localized AgP (LAgP) group and -1480C>G and -6106A>T SNPs (p=0.007 and 0.010, respectively). Among Caucasians the genotypes IL6 -1480 CC and -6106 TT increased the adjusted OR for LAgP (OR=3.09 and 2.27, respectively). This study supports the hypothesis that IL6 polymorphisms and haplotypes are moderately associated with periodontitis, possibly acting through influencing tissue levels of IL6. This association is stronger for LAgP than for other periodontal disease phenotypes.

Secretory lysosomes - a special mechanism of regulated secretion in haemopoietic cells.

The secretory granules o f cells derived from the haemopoietic lineage are 'secretory lysosomes' containing both lysosomal hydrolases and secretory proteins. Studies on cytotoxic T lymphocytes (CTLs) have elucidated several of the mechanisms that regulate protein sorting to, and secretion from, this unusual secretory organelle. In particular, recent findings from a CTL mutant have led to the hypothesis that CTLs, and other cells of the haemopoietic lineage, use specialized sorting and secretory mechanisms in which the lysosome functions as a regulated secretory granule.

The arguments for pre-existing early and late endosomes.

The past decade has seen the elucidation of many of the events and processes responsible for receptor-mediated endocytosis. However, a fundamental question about the endocytic pathway remains unresolved: do early endosomes mature into late endosomes, or are these two distinct and pre-existing cellular organelles? General opinion tends to favour the former possibility, to the point where one poster session at the recent American Society for Cell Biology meeting was entitled 'Maturation of Endosomes'. This article draws together new data arguing in favour of pre-existing early and late endosomes, between which transport occurs by vesicle budding and fusion.

The immunofluorescent era of membrane traffic.

In recent years immunofluorescence microscopy has been increasingly used to study membrane traffic. In this article seven electron microscopists, all with considerable experience in using light microscopy, take a critical look at the immunofluorescence approach and argue that results obtained with this method are often overinterpreted.

Granzymes A and B are targeted to the lytic granules of lymphocytes by the mannose-6-phosphate receptor.

To investigate the question of whether lytic granules share a common biogenesis with lysosomes, cloned cytolytic T cell lines were derived from a patient with I-cell disease. The targeting of two soluble lytic granule components, granzymes A and B, was studied in these cells which lack a functional mannose-6-phosphate (Man-6-P) receptor-mediated pathway to lysosomes. Using antibodies and enzymatic substrates to detect the lytic proteins, I-cells were found to constitutively secrete granzymes A and B in contrast to normal cells in which these proteins were stored for regulated secretion. These results suggest that granzymes A and B are normally targeted to the lytic granules of activated lymphocytes by the Man-6-P receptor. In normal cells, the granzymes bear Man-6-P residues, since the oligosaccharide side chains of granzymes A and B, as well as radioactive phosphate on granzyme A from labeled cells, were removed by endoglycosidase H (Endo H). However, in I-cells, granzymes cannot bear Man-6-P and granzyme B acquires complex glycans, becoming Endo H resistant. Although the levels of granzymes A and B in cytolytic I-cell lymphocytes are < 30% of the normal levels, immunolocalization and cell fractionation of granzyme A demonstrated that this reduced amount is correctly localized in the lytic granules. Therefore, a Man-6-P receptor-independent pathway to the lytic granules must also exist. Cathepsin B colocalizes with granzyme A in both normal and I-cells indicating that lysosomal proteins can also use the Man-6-P receptor-independent pathway in these cells. The complete overlap of these lysosomal and lytic markers implies that the lytic granules perform both lysosomal and secretory roles in cytolytic lymphocytes. The secretory role of lytic granules formed by the Man-6-P receptor-independent pathway is intact as assessed by the ability of I-cell lymphocytes to lyse target cells by regulated secretion.