A simple competitive assay to determine peptide affinity for HLA class II molecules: a useful tool for epitope prediction.

We have designed a cytometry-based competition assay to evaluate peptide binding to empty recombinant HLA class II molecules. The efficiency of this assay was evaluated using recombinant HLA-DP0401 molecules (HLA-DP) produced in insect cells and 13 peptides from human telomerase reverse transcriptase (hTERT). We demonstrate that our method allowed accurate measurements of peptide Ki values and can thus discriminate strong, moderate and poor HLA-DP binders. In parallel, we showed that among hTERT peptides, the most immunodominant in healthy individuals were those with moderate affinity for HLA-DP while no T cell response could be evidenced against peptides with very strong or very low affinities for HLA-DP. This strongly suggests that the precise determination of peptide affinity with our method can improve HLA class II epitope prediction.

Evidence of extranuclear cell sensitivity to alpha-particle radiation using a microdosimetric model. I. Presentation and validation of a microdosimetric model.

A microdosimetric model that makes it possible to consider the numerous biological and physical parameters of cellular alpha-particle irradiation by radiolabeled mAbs was developed. It allows for the calculation of single-hit and multi-hit distributions of specific energy within a cell nucleus or a whole cell in any irradiation configuration. Cells are considered either to be isolated or to be packed in a monolayer or a spheroid. The method of calculating energy deposits is analytical and is based on the continuous-slowing-down approximation. A model of cell survival, calculated from the microdosimetric spectra and the microdosimetric radiosensitivity, z(0), was also developed. The algorithm of calculations was validated by comparison with two general Monte Carlo codes: MCNPX and Geant4. Microdosimetric spectra determined by these three codes showed good agreement for numerous geometrical configurations. The analytical method was far more efficient in terms of calculation time: A gain of more than 1000 was observed when using our model compared with Monte Carlo calculations. Good agreements were also observed with previously published results.

Evidence of extranuclear cell sensitivity to alpha-particle radiation using a microdosimetric model. II. Application of the microdosimetric model to experimental results.

A microdosimetric model was used to analyze the results of experimental studies on cells of two lymphoid cell lines (T2 and Ada) irradiated with (213)Bi-radiolabeled antibodies. These antibodies targeted MHC/peptide complexes. The density of target antigen could be modulated by varying the concentration of the peptide loaded onto the cells. This offered the possibility of changing the ratio of specific (from cell-bound antibody) to non-specific (from antibody present in the supernatant) irradiation. For both cell lines, survival plotted as a function of the mean absorbed dose was a decreasing exponential. For the T2 cells, the microdosimetric sensitivity calculated for the whole cell was equal whether the irradiation was non-specific (z(0) = 0.12 +/- 0.02 Gy) or specific (z(0) = 0.12 +/- 0.09 Gy). Similar results were obtained for Ada cells. These results constitute a biological validation of the microdosimetric model. For both cells, the measured cell mortality was greater than the percentage of hit cells calculated with the model at low mean absorbed doses. This observation thus suggests bystander effects. It poses the question of the relevance of the mean absorbed dose to the cell nuclei. A new concept in cellular dosimetry taking into account cytoplasm or membrane irradiation and bystander modeling appears to be needed.

[Cryosurgery of basal cell carcinoma: a study of 358 patients]. / Cryochirurgie des carcinomes basocellulaires: étude de 358 malades.

INTRODUCTION: Cryosurgery is a well-established therapeutic modality for basal cell carcinoma. We report herein an important series of basal cell carcinoma treated by cryosurgery, with a five year cure rate evaluation. PATIENTS AND METHOD: Retrospective study with 395 basal cell carcinomas (over 358 patients - sex ratio H/F: 0.85) treated by cryosurgery between 1981 and 1992. For each patient the data were: age, sex, size of the lesion, location, clinical sub-type, tissue-temperature monitoring, recurrence date and esthetic outcome. RESULT: The lesions were located on the face (93 p. 100) and back (7 p. 100). Mean size was 17 mm. Clinical sub-types were known for 178 lesions; 11 p. 100 of BCC were morpheaform. Tissue-temperature monitoring was performed for 55 p. 100 of cases. 111 tumors were observed for more than 5 years. The 5-year actuarial failure rate was 9 p. 100. The 5-year cure rate was not significantly altered by sex, size of lesions, location and clinical sub-type. No frequent recurrences were observed when tissue-temperature monitoring had not been performed. Complications were rare and esthetic outcome was good. DISCUSSION: The 5-year actuarial recurrence rate with cryosurgery is similar to conventional surgery. It is not essential to control tissue-temperature for preventing recurrences. Cryosurgery is a reliable treatment and outcome depends on surgeon experience. Quickness and low cost of this procedure argue for choosing cryosurgery when treating elderly patients.

[Multiple isolated cutaneous myxomas]. / Myxomes cutanés multiples isolés.

INTRODUCTION: Cutaneous myxomas are rare. They are more often single; when they are multiple, they may be one of the component of the Carney's syndrome. CASE REPORT: We report a case of multiple and isolated cutaneous myxomas arising at 19 year-old. Diagnosis was confirmed by histologic studies. Examination failed to reveal other cutaneous or visceral features. DISCUSSION: The multiplicity of cutaneous myxomas is an essential element for diagnosis of Carney's syndrome; other components and notably atrial myxomas can appeared over time. Normal visceral explorations don't eliminated the diagnosis, and follow-up including screening echocardiography must be ensured before concluding, as in our case, as multiple and isolated cutaneous myxomas.