Relationship between peptide binding and T cell epitope selection: a study with subtypes of HLA-B27

The effect of HLA-B27 polymorphism on antigen presentation was analysed by comparing the binding of three Epstein-Barr virus-derived peptide epitopes to HLA-B27 subtypes with their immunogenicity and antigenicity in the context of these subtypes. The effect of altering the major anchor residue Arg2 on binding or on recognition by peptide-specific cytotoxic T lymphocytes (CTL) was also examined. The three peptides bound significantly to all the B*2701-B*2706 subtypes. This did not correlate with the peptides being immunogenic or recognized by specific CTL in the context of only particular subtypes. In addition, of the three viral epitopes tested, those that were immunogenic in B*2702- or B*2705-restricted responses bound to these subtypes less efficiently than one peptide that was immunogenic only in the B*2704 context. Thus, among several potentially immunogenic peptides from the same virus, the antiviral response is not necessarily directed against the one that binds best to the restricting subtype. These results indicate that HLA- B27 polymorphism influences antigen presentation in ways other than simply peptide affinity. Synthetic analogues lacking the canonical Arg2 motif of HLA-B27-bound peptides, even when binding much worse to the restricting subtype, were recognized equally by CTL specific for the parental peptide. This indicates that Arg2 is not required to maintain the structure of the epitope. The implications of these results for pathogenetic models of HLA-B27-associated disease are discussed.      

Positive margins in basal cell carcinoma: relationship to clinical features and recurrence risk. A retrospective study of 248 patients

BACKGROUND: Incomplete resection of a basal cell carcinoma does not necessarily imply tumour recurrence. OBJECTIVE: The purpose of our study was to determine the clinical features most often associated with positive surgical margins and to establish whether positive margins effectively imply tumour recurrence. METHODS: We did a retrospective evaluation of 273 basal cell carcinomas in a total of 248 subjects. For each case, data regarding tumour location, sex, histological type and the presence or absence of affected surgical margins were collected. Follow-up was available in 151 cases. RESULTS: Positive margins were most often observed in facial lesions, particularly in the nasal and perioral areas, and for morphoeic histological types. Tumours with margin involvement exhibited a higher recurrence rate (26%) than those with free margins (14%) over a 5-year follow-up period. CONCLUSIONS: Individualized management, with special considerations depending on tumour location and histological type, is needed to treat basal cell carcinomas and cases with affected margins. Re-excision, preferably with Mohs' surgery, is advised in the latter as recurrences are much more complicated to treat. Furthermore, all cases need adequate follow-up, even in cases with unaffected surgical margins.     

Role of endothelial cells in restenosis after coronary angioplasty

Summary— Percutaneous transluminal coronary angioplasty (PTCA) is today a procedure of choice in many patients with atherosclerotic coronary artery disease. Despite high rates of initial success, restenosis, occurring in 30 to 40 percent of patients within the first six months, remains the major problem limiting the long-term efficacy of the procedure. Animal models have enhanced our knowledge in the understanding of the mechanisms involved in the restenotic process after experimental angioplasty. In fact, the two known determinants of restenosis are the proliferative and migrative response of underlying smooth muscle cells with production of extracellular matrix and the recently highlighted vascular remodeling. Endothelium, which regenerates from the leading edge of the de-endothelialized area within the weeks following arterial injury, is of particular interest in the modulation of the healing process after the procedure. Endothelial dysfunction, as an imbalance between relaxing and contracting factors, between anti- and procoagulant mediators or growth-inhibiting and growth-promoting factors, occurs at sites of regenerating endothelium. Experimental studies, using drugs that enhance endothelium-derived relaxing factors release or drugs that diminish endothelium-derived contracting factors production, have often been shown to be effective in the restenosis prevention. Thus, impairment in endothelial cell function may be considered as one of the major regulatory element in the restenotic process. This review discusses the interactions between endothelial and smooth muscle cells and has for aim to point out the major role of endothelial cells in the development of neointimal thickening and arterial remodeling.     

The relationship of blood transfusion, tumor staging, and cancer recurrence

Previous research demonstrated a relationship between transfusions of whole blood, or large numbers of red cell concentrates, and later recurrence of cancers of the colon, rectum, cervix, and prostate. It is possible that the transfusion of whole blood may represent a surrogate marker for advanced or more aggressive clinical disease. The relationship of clinical or histologic tumor stage, blood transfusion status, and disease outcome was studied in detail. Patients receiving no transfusions or small numbers of red cells (less than or equal to 3 units) had uniformly better recurrence and survival experiences than patients receiving similar amounts of blood that included at least 1 unit of whole blood, regardless of the patient's clinical or histologic tumor stage. In multivariate analyses, stage was an independent predictor of outcome, and transfusion status was not a surrogate marker for stage. The effects on recurrence of stage and transfusion appear to be cumulative. These results are consistent with but do not prove the hypothesis that the transfusion of large amounts of stored plasma and cellular debris impairs the host defenses against cancer, regardless of the underlying biologic and clinical aggressiveness of the cancer.     

A polymerase chain reaction study of the stability of Ig heavy-chain and T-cell receptor delta gene rearrangements between presentation and relapse of childhood B-lineage acute lymphoblastic leukemia

Ig heavy-chain (IgH) and partial V delta 2-D delta 3 T-cell receptor (TCR) gene rearrangements were investigated, by polymerase chain reaction (PCR) amplification and sequence analysis, in 52 patients at presentation and first relapse and in 14 at both first and second relapse of B-lineage acute lymphoblastic leukemia. In combination, these techniques amplified one or more clonal markers at presentation in 90% of patients (IgH-PCR, 75%; V delta 2-D delta 3-PCR, 46%; both, 33%). Changes in the pattern of amplification between presentation and first relapse were seen in 31% of patients positive by IgH-PCR at presentation and in 25% of those positive by TCR delta-PCR. Only 3 patients showed complete change in their rearrangements, which is suggestive of relapse with a new clone. Furthermore, despite the high reported rates of oligoclonality and clonal evolution at the IgH locus, the results presented show that false-negative minimal residual disease (MRD) detection can be avoided by designing D-N-J probes to all presentation rearrangements. Using a PCR approach for both gene markers, false-negative testing because of clonal evolution would have only occurred in 3 (8%) of the IgH-positive patients, in contrast to 5 (21%) of V delta 2-D delta 3-positive patients. Combining these two systems increases the proportion of patients open to study to 90%, allows comparative studies of the sensitive of the two methods, and reduces the rate of false-negative assessment of MRD caused by clonal evolution to less than 10%. We conclude that large prospective PCR studies of MRD detection should examine gene rearrangements at multiple loci to maximize their applicability and to minimize false-negative relapse prediction.     

Stage IB,IIA and proximal IIB,carcinoma of the uterine cervix,treated by irradiation alone or in combination with surgery

This is a report of a nonrandomized comparison of treatment results of 139 patients with stage IB, IIA and proximal IIB carcinoma of the uterine cervix treated by radiation alone and 113 treated with a combination of radiation and surgery. The five-year tumor free acturial survival for the patients with stage IB either with irradiation alone (RT) or combined with surgery (RS) was approximately 87%. For stage II the tumor free actuarial five-year survival 79% with patients of RS, and 76% with RT. In the 113 patients treated with RS there were 18 (16%). In the 139 patients treated by RT there were 18 (13%) recurrences of pelvic, 4 local recurrences, 11 combined with parametrial, and free parametrial recurrences. There was no significant difference in the survival and recurrence rate of the patients treated with either method. Major complications were comparable in both groups (RT approximately 25% and RS approximately 10%), but 2/3 of those complications recovered without sequelae. The most frequent minor complication in the patients treated with RT was rectosigmoiditis.     

Proarrhythmic effects of a quinidine analog in dogs with chronic A-V block

Summary— The proarrhythmic effects of 3-hydroxy-hydroquinidine (3-OH-HQ) and quinidine were compared in a canine model of QT-dependent ventricular arrhythmias. Eight hypokalemic ([K+] ≤ 3.2 mmol/l) dogs with AV block (around 45 bpm) were given either drug in a randomized order at 2-day intervals. Each drug was given as two 1 hour doses, with a bolus (low dose: 5 mg/kg or high dose: 10 mg/kg) plus infusion (25 or 50 μg/kg/min) protocol. Propranolol infusion was combined with a third hour of the high dose infusion. Electrophysiologic measurements were performed at baseline and 30 minutes after the beginning of each dose and propranolol infusion, and proarrhythmic events were recorded 30 minutes before and during the experiment. Neither drugs altered the ventricular cycle length. Quinidine and 3-OH-HQ prolonged the QT interval similarly and significantly when paced at 60 bpm after the low dose (+ 39 ± 18 and + 28 ± 22 msec, respectively) and after the high dose (+ 51 ± 29 and + 50 ± 22 msec). Quinidine was more arrhythmogenic than 3-OH-HQ: 7/8 dogs (p ≤ 0.05) developed ventricular arrhythmias (isolated, repetitive ventricular beats, or polymorphic ventricular tachycardias) during quinidine infusion (low dose: 4 dogs) compared to 3/8 dogs (NS) during 3-OH-HQ infusion (low dose: 1 dog). Addition of propranolol-induced bradycardia (around 30 bpm) caused torsades de pointes (wave burst arrhythmias) or polymorphic ventricular tachycardias after both drugs (in 3 dogs after quinidine and in 2 dogs after 3-OH-HQ). Thus 3-OH-HQ was slightly less arrhythmogenic than quinidine in this model of torsades de pointes, but the addition of an extra favouring factor (bradycardia) reduced that difference.     

Cerebrospinal fluid shunts: flow measurements with MR imaging

The authors describe a technique for determination of shunt patency by quantifying cerebrospinal fluid shunt flow rates with magnetic resonance (MR) imaging. This method uses a modified clinical sequence that is both sensitive to slow flow perpendicular to the imaging plane and capable of achieving oblique angles with a 4-cm field of view. Velocity-dependent phase images were used to quantify flow rates within the shunt. A preliminary study was performed in seven patients with hydrocephalus and cerebrospinal fluid shunts. Two patients were found to have zero flow in the shunt, while the remaining five had flow rates ranging from 4 to 19 mL/h. Results showed that the measurement of flow rates within the shunt lumen with MR imaging is clinically feasible.