Malignant colorectal obstruction treated by means of self-expanding metallic stents: effectiveness before surgery and in palliation

PURPOSE

To determine the effectiveness and safety of metallic stents in the treatment of malignant colorectal obstruction before surgery and for palliation.

MATERIALS AND METHODS

Eighty patients with acute malignant colorectal obstruction presumed to be malignant were treated by means of implanting self-expanding metallic stents.

RESULTS

Stent placement was successful in 70 of the 80 patients and resolved bowel obstruction in 67 patients (96%). Two patients had colonic perforation and developed peritonitis 18 and 24 hours after stent placement; one patient died as a consequence. Thirty-three patients underwent elective surgery after 7 days +/- 3 (SD; range, 4-10 days), and adequate tumoral coverage and cleansing of the colon were observed in all patients. Stent placement was used as final palliative treatment in another 35 patients. Patient follow-up lasted a mean of 138 days +/- 93 (range, 36-334 days). The survival rate for the palliative group was 55% at 3 months, 44% at 6 months, and 25% at 9 months. The estimated primary stent patency rate was 91% at 3 and 6 months.

CONCLUSION

Management of colorectal obstruction by using metallic stents was effective and safe, although colonic perforation is a potential complication. In cases of palliation, the method may obviate palliative colostomy.

[Kasai operation in the age of liver transplantation. Healing or merely palliative technique?]

AIM

To assess the results of portoenteroanastomosis (PEA) and liver transplantation (OLT) in extrahepatic biliary atresia (EHBA).

METHODS

Out of a series of 148 EHBA, 92 cases primarily treated by us were selected. Survival with the native liver (end point = death or OLT) and its relationship with the age at PEA, type of EHBA, ductal size and bile flow restablishment were assessed. Patient survival was compared in those patients who had access to OLT when needed (Group I, n = 69) and those in whom only PEA was available (Group II, n = 23). (OLT program started in january 1986).

RESULTS

At the end of follow-up, 32 children are alive with their native livers, 22 died and 38 had OLT. 40/85 patients who underwent PEA had complete restablishment of bile flow (47%). The no failure rate (survival of the native liver) at 1, 5, 10 and 20 years, was 91%, 49%, 38% and 21%, respectively. Bile flow restablishment was the only predictor significantly associated with good prognosis (survival of native liver at 5, 10 and 20 years of 89%, 86% and 51%, respectively). Differences in survival were significant (p < 0.001) between patients in groups I and II at 1 year (92% vs 74%), 5 years (78% vs 35%), 10 years (76% vs 30%) and 20 years (76% vs 30%).

CONCLUSIONS

Bile flow restablishment after PEA can be obtained in experienced centers in about 50% of cases of EHBA. The combined and sequential use of PEA and OLT allows excellent long-term survival in EHBA.

[New approach in the surgical treatment of the urogenital sinus]

The urogenital sinus is an embriological anomaly which consists on a common channel from the urethra and vagina. The major incidence is produced in the congenital adrenal hyperplasia's context. In certain occasions it can be associated to an imperforate anus, then the malformation is called a cloacal defect. There are multiple surgical techniques to correct this malformation and different therapeutical approaches (without surgery, surgery at one or various times, early or delayed surgery) being the newest one the total urogenital mobilization. The purpose of this work is to reflect our experience with this technique. We present seven girls with urogenital sinus (3 with congenital adrenal hyperplasia, 2 with a cloacal defect, and the other 2 associated to ambiguous genitalia). Five patients were operated in the first year of life. The outcome has been favorable, and the cosmetic and functional results have been very good. The surgical technique consists on posterior sagittal incision, it can be done transanorectal if necessary, the urethrovaginal union is achieved and both structures are mobilized together, connecting them to the perineum, as a single unit. We believe that the total urogenital mobilization is actually the surgical technique to be chosen in every of urogenital sinus, for being easier, allowing early realization (girls under 1 year old), correcting simultaneously other anomalies, reducing the complications (urethrovaginal fistula, vaginal structure, or acquired vaginal atresia); and the result is excellent.

Identification of phosphorylation sites in proteins by nanospray quadrupole ion trap mass spectrometry

A method is described for identifying serine phosphorylation sites in proteins, based on conventional (32)P labeling followed by electrophoretic separation, 'in-gel' digestion with a protease, peptide extraction, reversed-phase high-performance liquid chromatographic separation and collection and off-line analysis of the radioactive fractions by nanospray ion trap mass spectrometry. The method was successfully applied to the identification of three phosphorylation sites in two proteins which were subjected to in vitro phosphorylation under physiological conditions. Different combinations of the various scanning modes of the ion trap, including high-resolution, multiple subfragmentation (or MS(n)) and fast scan analysis, were employed to identify the phosphopeptides, determine their sequence and localize the exact site of phosphorylation. 'Blind' fragmentation using fast scans was used to analyze a phosphopeptide which was undetectable in other scanning modes. The sequence, phosphorylation site and double cysteine modification of the potassium adduct of a peptide containing 35 residues were also determined by multiple fragmentation. The results not only support the validity of the proposed method for routine identification of phosphorylation sites, but also demonstrate the exceptional capability of off-line ion trap mass spectrometry in combination with nanospray ionization for performing very detailed studies on the structure of peptides.

Expression and clinical significance of apolipoprotein D in epithelial ovarian carcinomas

OBJECTIVE

Apolipoprotein D is a protein component of the human plasma lipid transport system but is also associated with a more favorable prognosis in women with breast cancer. This retrospective study was undertaken to examine the tumoral expression of apolipoprotein D in epithelial ovarian cancer and to analyze the possible correlation with tumor and patient characteristics as well as androgen receptors and their prognostic significance.

METHODS

Immunohistochemical evaluation was used to examine apolipoprotein D expression in paraffin blocks from 68 epithelial ovarian carcinomas.

RESULTS

A total of 18 (26.4%) tumors stained positively. No significant correlation was found between apolipoprotein D expression and patient or tumor characteristics and androgen receptor status. However, apolipoprotein D expression was significantly associated with prognosis in patients with residual tumor greater than 1 cm. Thus, patients with apolipoprotein-D-negative tumors had a poorer overall survival than those with apolipoprotein-D-positive tumors (P = 0.039). In addition, multivariate analysis demonstrated that apolipoprotein D expression was an independent prognostic factor with initial tumor size in this group of patients (P = 0.005).

CONCLUSIONS

Our results led us to consider the existence of apolipoprotein D expression by a significative percentage of ovarian carcinomas, and this protein expression might be of clinical usefulness for identifying lesions with different evolution.

[Analysis of treatment failure in pediatric subglottic stenosis]

BACKGROUND

The good results obtained until nowadays in the surgery of subglottic stenosis is followed by an analysis of the failures.

METHODS

We study retrospectively 48 cases treated in the last eight years in two institutions. Study variables were: age, previous diagnosis, grade os the stenosis, surgical treatment, complications and evolution.

RESULTS

Mean age was 2.8 +/- 0.43 years (newborn-17 years). In 13 cases (27%) the result obtained was considered a failure. Failure indexes were: treatment selection (7,7%), surgical technique selection (23%), due to the technique itself (23%), iatrogenia (15,4%), associated diseases (30,7%). Mortality of the series was 8.3%.

CONCLUSIONS

The learning curve of these techniques is difficult although once the necessary experience is achieved the results are excellent.

Limited diversity of peptides related to an alloreactive T cell epitope in the HLA-B27-bound peptide repertoire results from restrictions at multiple steps along the processing-loading pathway

The influence of various factors along the processing-loading pathway in limiting the diversity of HLA-B27-bound peptides around a core protein sequence was analyzed. The C5 proteasome subunit-derived RRFFPYYV and RRFFPYYVY peptides are natural B*2705 ligands. The octamer is an allospecific CTL epitope. Digestion of a 27-mer fragment of C5 revealed that both ligands are generated from this precursor substrate with the 20S proteasome in vitro in a ratio comparable to that in the B*2705-bound peptide pool. The C5 sequence allowed to derive a nested set of six additional peptides with 8-11 residues containing the core octamer sequence and the Arg2 motif of HLA-B27, none of which was found in the B27-bound pool. Together, low proteasomal yield, disfavored TAP-binding motifs, and low affinity for B*2705 accounted for the absence of four of the six peptides. The two remaining differed from the natural octamer or nonamer ligands only by an additional N-terminal Ser residue. Their stability in complex with B*2705 was lower than the respective natural ligands, raising the possibility that N-terminal trimming might have favored a shift toward the more stable peptides. The results suggest that the B*2705-bound peptide repertoire has a highly restricted diversity around a core alloantigenic sequence. This is not explained by a single bottleneck feature, but by multiple factors, including proteasomal generation, TAP-binding motifs, MHC-binding efficiency, and perhaps optimized stability through N-terminal trimming. Tapasin-dependent restrictions, although not excluded, were not required to explain the absence in vivo of the particular peptide set in this study.

Meningococcal disease in a large urban population (Barcelona, 1987-1992): predictors of dismal prognosis. Barcelona Meningococcal Disease Surveillance Group

CONTEXT

Studies on meningococcal disease in large urban communities have rarely been performed and are usually based on passive epidemiologic surveillance. Active surveillance may provide new insights.

OBJECTIVES

To determine epidemiologic, clinical, and bacteriological characteristics and predictors of dismal prognosis (death and sequelae) in meningococcal disease.

DESIGN

Prospective, population-based study.

SETTING

All the acute care hospitals (n = 24) in Barcelona, Spain.

PATIENT

The 643 patients whose conditions were diagnosed from 1987 through 1992 were detected by 2 active surveillance methods.

OUTCOME MEASURES

Incidence and notification to Public Health Service. Clinical and bacteriological features were determined. Dismal prognosis predictors were determined by logistic regression.

RESULTS

Average annual incidence was 6.41 per 100,000 inhabitants, with no clear trend of change (P = .08). Sensitivity of the Public Health Service surveillance system was 69.1%. Children younger than 10 years from the inner city were at higher risk than those from the highest income district (relative risk, 3.00; 95% confidence interval [CI], 1.84-5.06). Increasing annual incidence of serogroup C (0.82-1.29/100,000; P = .008) and decreasing incidence of serogroup B (5.11-2.82/100,000; P = .004) was noted. Average annual mortality was 0.40 per 100,000 inhabitants, while the annual average potential years of life lost was 18 per 100,000 inhabitants. Overall case-fatality rate was 6.4%. Independent predictors of death were hemorrhagic diathesis (odds ratio [OR], 63; 95% CI, 21-194), focal neurologic signs (OR, 10; 95% CI, 3-30), and age 60 years or older (OR, 6; 95% CI, 2-17), whereas preadmission antibiotic therapy was associated with favorable outcome (OR, 0.07; 95% CI, 0.02-0.3). Four percent of survivors presented with sequelae. Independent predictors of sequelae were hemorrhagic diathesis (OR, 21; 95% CI, 3-131), focal neurologic signs (OR, 16; 95% CI, 5-53), age 60 years or older (OR, 7; 95% CI, 2-26), and age between 15 and 59 years (OR, 5; 95% CI, 2-14), whereas preadmission antibiotic therapy had a protective effect (OR, 0.2; 95% CI, 0.04-0.5).

CONCLUSIONS

Active epidemiologic surveillance significantly improved detection of cases and allowed us to observe that meningococcal disease still causes much morbidity and mortality, especially among children living in the inner city. Hemorrhagic diathesis, focal neurologic signs, and age were independent predictors of dismal prognosis, whereas preadmission antibiotic therapy had a protective effect.

[The role of intraoperative radiotherapy in oncological pediatric surgery]

Conventional external beam radiation has proved its profit in pediatric tumors; but its complications have limited it in therapeutical approach. Intraoperative radiotherapy delivers a high single dose in residual tumor or high risk areas during surgery. In our center, during last two years, 7 patients have been candidates to surgery with intraoperative radiotherapy (the age range was between 5 months-17 years; mean 8.5 years). Two patients were excluded of our protocol because of their intraoperative stage. Patients tumors types were: neuroblastoma (n = 3; stage III and IV), soft tissue sarcomas (n = 1) and Ewing's sarcoma (n = 1). The radiation doses ranged from 500 cGyto-1200 cGy. Local control tumor was achieved in 4 patients and no-complications were present secondary to surgery or intraoperative radiotherapy. Intraoperative radiotherapy seems to be a feasible treatment which might promote local control in pediatric tumors with protection of normal tissues and could be an excellent complement in special cases.

[Extracorporeal respiratory assistance (ECRA): initial experiences in Spain]

The attendance respiratory extracorporeal (AREC) is an oxygenation form for membrane extracorporeal with flow tidal and veno-venous cannula described by Chevalier et al. in 1990. We present our clinical experience so much with AREC in system veno-venous flow tidal as veno-arterial. From october of 1997 until the present time we have treated three patients by means AREC, in two patients with veno-venous system and in one veno-arterial. In all the cases bomb Collin-Cardio has been used with bladder for flow tidal and membrane of oxygenation of 0.8 m2, being inserted a system of alternative clamp of the branches of the circuit. The system AREC has been used in two patients with congenial diaphragmatic hernia, right in a case and left in the other one. The gestational age was of 38 and 36 weeks with a weight of 3,200 and 2,900 grams. Both patients were remitted from other centers by failure of the conventional treatment. In both cases the indication of AREC was the sharp deterioration of the general state with failure of the conservative treatment, being the previous oxygenation index of 109 and 112. The third patient precised veno-arterial AREC for ventricular failure during the correction of the congenital heart disease, this patient was 5 month old and the weight was 5,000 grams. The duration of AREC in the cases of congenital diaphragmatic hernia was of 14 and 10 days. In a patient the diaphragmatic hernia was corrected at the 55 hours of being in AREC. In the second case the hernia had been surgical corrected in another center. The exit of AREC in both cases carries out after a discreet improvement of the lung function. Both patients died at the 24 and 48 hours of the decannulation for cerebral hemorrhage and respiratory failure. The third patient stayed stable in veno-arterial AREC during 4 days, with hemodynamic support of 130 ml/kg/min, retiring the support to present absence of cerebral activity.

CONCLUSIONS

With the derived limitations of the extreme severity of the treated cases and the current phase of beginning of the AREC team, we think that it is a useful and available technique in our country, for the handling of patient with cardiorespiratory failure while waiting for improvement of their base pathology.

[Indications from the laparoscopic approach in pediatric urological surgery: our experience in 49 patients]

OBJECTIVES

To analyse the diagnostic and therapeutic potential of video-assisted laparoscopy in the urology paediatric pathology. We had analysed its indications and results, to measure in disminution of morbidity and hospital stay.

PATIENTS AND METHODS

We are treated in our section of Paediatric Urology 49 patients during the period of June 1995 and December 1998, performing 51 laparoscopics procedures. The mean age was 8 years (2-16 years ago). The laparoscopic indications were diagnostic in 33 patients: intra-abdominal testes (n = 16), renal biopsy (n = 17), and terapeuthics in 16 patients (17 laparoscopics procedures): varicoceltomy (n = 7), orchiectomy (n = 1), closure peritoneal-vaginal duct (n = 2), retroperitoneal nephrectomy (n = 6), marsupilazation and omentoplastic in giant lymphocel renal post-transplantation (n = 2).

RESULTS

The laparoscopic approach were effective in 100% of diagnostic procedures and 93.4% of therapeuticm procedures. Conversion in 2 cases were necessary to make renal biopsy (n = 1). We hadn't have postoperatives complications and the indices of intraoperative morbidity was of 2.4%. The mean hospital stay was 1.4 days.

CONCLUSIONS

We believe that exist indications clinically stabilised of laparoscopic approach--diagnostic and therapeutic--in paediatric urology. There are others indications that its are consider anecdotal in the present but in immediately future these indications will be valid.

The porcine 2A10 antigen is homologous to human CD163 and related to macrophage differentiation

The mAb 2A10 recognizes a 120-kDa protein with sequence homology to the human CD163 and whose expression is restricted to the cells of the porcine monocyte/macrophage lineage. While most of tissue macrophages express high levels of 2A10 Ag, bone marrow cells and a subset of blood monocytes are negative for this marker. The percentage of 2A10+ blood monocytes ranges between 5-50% depending on the donor. The phenotypic analysis indicates that these cells are more similar to mature macrophages than 2A10- monocytes. 2A10+ monocytes express higher levels of swine histocompatibility leukocyte Ag II, CD16, and the adhesion molecules very late Ag-4 (CD49d) and LFA-1 (CD11a) than 2A10- monocytes, while CD14 and SWC1 expression is lower. Both monocyte subsets also differ in their functional capabilities. 2A10+ monocytes induce a greater allogeneic response on T lymphocytes than 2A10- cells. LPS-stimulated 2A10+ and 2A10- monocytes both produce proinflammatory cytokines (TNF-alpha and IL-1alpha), but antiinflammatory IL-10 is only detected on the latter population. When 2A10- monocytes were cultured in medium containing pig serum, they acquired some phenotypic features of 2A10+ cells, expressing the 2A10 Ag. In contrast, when they were cultured in the presence of L929 supernatant as a source of GM-CSF, the 2A10 Ag expression remained low, scarcely increasing over basal levels. 2A10+ cells cultured with pig serum developed features that resemble monocyte-derived dendritic cells. These results indicate that 2A10+ monocytes could constitute a cell population in a more advanced maturation stage than 2A10- circulating monocytes.

[Thyroid tumors in childhood]

The thyroid pathology in the paediatric population represents 5% of the total and 1.2% only thyroid pathology correspond to the infantile solitary thyroid nodules. Most of them are asymptomatic and as only sign an increase of volume is observed in the neck. Always we have to ask about the family history because the possibility of medullary carcinoma related with multiple endocrine neoplasias should be investigated (a patient of our series). The thyroid tumor represents 0.5% of all the tumors and of these 10% is in younger than 21 years old. We present 13 patients with thyroid pathology that have required surgical treatment, since 1983 to 1997. Five papillary carcinomas (ages: 7 to 14 years old) that started with a cervical nodule, normal thyroid function and a case of medullary carcinoma, in a multiple endocrine neoplasia (MEN II 2A). In the 5 cases of carcinoma papillary we were carried out total thyroidectomy and later on, postoperative ablative dose of 131I was administered. In the case of the girl with medullary carcinoma was carried out a total tumorectomy and lymph node excision. Finally, seven patients with nodule thyroid were thyroid benign tumors (benign 6 adenomas and 1 cyst colloid, ages: 8 to 15 years old). In all of them we were carried out total surgical excision of the thyroid nodules. Our protocol of study of nodule thyroid includes: 1) thyroid gammagraphy to know the intensity of reception of the isotope; 2) cervical ultrasound; and 3) biopsy or cytopathology of fine needle aspiration of the thyroid gland in children that it dissuades to base the surgical strategy on this test.

[Sigmoid neovagina: apropos of 2 cases]

The presence of ambiguous external genitals can be related with a number of nosologic entities. We can find the female form with hypertrophic clitoris and vaginal hypoplasia in a wide variety of phenotype presentations. We have two young girls with ambiguous external genitals, where we notice hypertrophic clitoris and vaginal hypoplasia, with the diagnosis of mixed gonadal dysgenesis and androgen insensitivity syndrome (Morri's Syndrome). They have been operated several times: gonadectomy, genitoplasty, vaginoplasty and mammoplasty. We have made a neovagina, using a segment of sigma and preserving the walls of the former vagina. The surgical technique we used, consisted in the abdominoperineal descent of the segment of sigmoid colon and anastomosis with the back wall of the former vagina and the perineum; after that, we split the intervaginal septum, linking these two structures and reaching a lonely introitus vaginae. The hormonal treatment for the girl with mixed gonadal dysgenesis with estrogen and progestogen induces normal menstruations; we only use estrogen for the patient with Morri's Syndrome. The histology showed that there were dysgenetic gonads in one of the patients and testicular tissue without gonadal elements. Both girls have had a good evolution, with no problems and an excellent aesthetic and functional result.

The South Amerindian allotype HLA-B*3909 has the largest known similarity in peptide specificity and common natural ligands with HLA-B27

HLA-B*3909 has only been found among South Amerindians, and presumably arose locally in these populations. It differs from B*3901 by a single Tyr to Ser change at position 99. To analyze the influence of this polymorphism on peptide specificity, pool sequence analysis and sequencing of multiple individual ligands from B*3901 and B*3909 were carried out. Both allotypes bind peptides with Arg2 or His2 and nonpolar C-terminal residues. However, whereas His2 is the predominant B*3901 motif, a majority of the B*3909-bound peptides have Arg2. In addition, B*3909 binds peptides with Pro2, and also shows an increased preference for Pro3. In spite of their differences, both subtypes bind overlapping peptide repertoires, as indicated by the identification of several identical ligands from their respective peptide pools. B*3909 is significantly more similar in its peptide specificity to HLA-B27 than B*3901. This is due to the increased preference of B*3909 for Arg2 and to low suitability of HLA-B27 for His2. The similarity between HLA-B27 and B*3909 was confirmed by identification of a natural ligand common to both allotypes. In addition, multiple HLA-B27 ligands bound efficiently B*3909 in vitro. The results indicate that, among the HLA class I allotypes of known peptide specificity, B*3909 is the most similar in its peptide binding properties to HLA-B27, which is absent in South Amerindians. This may have implications for the susceptibility of individuals in these populations to spondyloarthropathies.

Transcription factor AP-2 activity is modulated by protein kinase A-mediated phosphorylation

We recently reported that APOE promoter activity is stimulated by cAMP, this effect being mediated by factor AP-2 [Garcia et al. (1996) J. Neurosci. 16, 7550-7556]. Here, we study whether cAMP-induced phosphorylation modulates the activity of AP-2. Recombinant AP-2 was phosphorylated in vitro by protein kinase A (PKA) at Ser239. Mutation of Ser239 to Ala abolished in vitro phosphorylation of AP-2 by PKA, but not the DNA binding activity of AP-2. Cotransfection studies showed that PKA stimulated the effect of AP-2 on the APOE promoter, but not that of the S239A mutant. Therefore, cAMP may modulate AP-2 activity by PKA-induced phosphorylation of this factor.

[Hemodynamics and oxygenation in experimental lung lobe transplantation]

INTRODUCTION

Lung transplantation is the only valid treatment for the severe neonatal pulmonary hypoplasia. The objective of this work is to develop and to establish a model of lobar lung transplantation.

MATERIAL AND METHODS

Twenty pigs were used. Neonates 2-3 weeks; adults 10-12 weeks. Donors weighed 15 to 20 kg and recipients 5 to 7. In Group A animals were used to assess surgical anatomy and to develop surgical technique and instrumentation's model. The remainder animals (Group B) underwent left lobar lung transplantation. Hemodynamic and oxygenation data were collected before and after six hours of right lung exclusion.

RESULTS

All animals tolerated right lung exclusion. There was a significant increase in mean pulmonary artery pressure and a sustained reduction in cardiac output. Oxygenation values were not affected during unilateral lung perfusion.

CONCLUSIONS

The neonatal pig has a good tolerance to reduced-size lung transplantation. Lobar lung transplantation could increase substantially the donor's lung pool.

[Hemodynamic changes during laparoscopic surgery. Preliminary study]

The haemodynamic changes produced by laparoscopic surgery in children have been evaluated. A transesophageal echocardiographic study on 13 patients (7 males and 6 females, 10.8 +/- 2.7 years old) has been performed before, during and after peritoneal CO2 gas insufflation. A change on the Doppler waves pattern of the infradiaphragmatic veins along with an increase in blood flow velocity were observed. Pulmonary veins suffered minimal changes showing an increase on either the systolic pressure and on atrial contraction. Diastolic retrograde flow in aorta reflected an increase in peripheral vascular resistance. Cardiac output increased minimally. All haemodynamic changes returned to basal after gas peritoneal desufflation. These data show that laparoscopic surgery could produce important cardiac derangements in children with ventricular dysfunction or in patients presenting left ventricular outlet obstruction. In these patients laparoscopic surgery might be precluded.

High-sensitivity analysis and sequencing of peptides and proteins by quadrupole ion trap mass spectrometry

This paper describes experience with the commercially available LCQ quadrupole ion trap mass spectrometer applied to the off-line analysis of peptides and proteins. The standard front end of the electrospray probe was replaced with a micromanipulator which, with the aid of a magnifying device, allowed the use of a variety of miniaturized spraying interfaces. The low sample consumption and extended analysis times of these devices were ideally suitable to obtain improved results in terms of sensitivity and mass accuracy. This needed a careful optimization of the number of ions stored inside the trap (ion target parameter) and required spectrum averaging of many scans. A method is presented for the mathematical fitting of ZoomScan spectra to theoretical isotopic distributions, which allowed the mass determination of large peptides with more accuracy than that achieved by conventional deconvolution algorithms. A very simple on-line desalting configuration is also described which needed no external micro-high-performance liquid chromatographic pumps, and can be easily mounted using the built-in syringe delivery system of the LCQ. This set-up allowed extended analysis times of 'in-gel' protein digests in subpicomole amounts. Finally, the multiple fragmentation capabilities of the ion trap were found to be extremely useful for the analysis of peptide modifications such as phosphorylation and for sequencing individual peptides from highly complex MHC-bound peptide pools.

The same natural ligand is involved in allorecognition of multiple HLA-B27 subtypes by a single T cell clone: role of peptide and the MHC molecule in alloreactivity

The human alloreactive CTL clone 27S69, raised against B*2705, cross-reacts with B*2702 and B*2703, but not with B*2701, B*2704, B*2706, or B*2710. Its natural epitope was identified by electrospray/ion trap mass spectrometry, as the proteasome-derived RRFFPYYV octamer. This is the first HLA-B27 ligand shown to be immunogenic in alloreactivity. The RRFFPYYVY nonamer, also found in the B*2705-bound peptide pool, was recognized much less efficiently, demonstrating that an alloreactive CTL distinguishes between very similar natural ligands. Molecular modeling suggested that this was due to the different conformation of each peptide in complex with B*2705. B*2702- and B*2703-RMA-S cells were lysed by CTL 27S69 when sensitized with the octamer, demonstrating that cross-reaction with these subtypes is through recognition of the same peptide as in B*2705. B*2704-, B*2706-, and B*2710-RMA-S cells were not sensitized for lysis, in spite of efficient binding of the octamer, indicating that polymorphism in these subtypes directly impairs allorecognition. B*2701-RMA-S and -C1R cells were sensitized for lysis by the octamer, suggesting lack of the endogenous peptide epitope on this subtype. Absence of the octamer in the B*2701-bound peptide pool further suggested that B*2701 polymorphism impairs the generation of this peptide.

A single amino acid change makes the peptide specificity of B*3910 unrelated to B*3901 and closer to a group of HLA-B proteins including the malaria-protecting allotype HLA-B53

HLA-B*3910, which has only been found in African and African American individuals, differs from B*3901 by the single amino acid change of Cys67 to Tyr67. Sequence analysis of the B*3910-bound peptide pool and of several individual ligands revealed that this subtype has strong preference for peptides with Pro2. This is in contrast with the preference of B*3901 for peptides with basic residues (Arg and His) at this position, and indicates that the single amino acid substitution between B*3910 and B*3901 totally changes the repertoire of bound peptides. This is presumably due to the significant decrease in the size of the B pocket, and to its increased hydrophobicity, since Tyr67 takes part in this pocket. B*3910 is similar to various other class I proteins in its preference for peptides with Pro2 and nonpolar C-terminal residues, including HLA-B53, an antigen associated with protection against severe malaria. The role of these two motifs as major peptidic anchors suggests that B*3910 and HLA-B53 may bind common peptides.