Abstract Cytotoxic T lymphocytes generated by sensitization of B10.BR {H-2k, Qa-1a) cells in vivo and in vitro with CBA or AKR (H-2k, Qa-1b) spleen cells were used to evaluate Qa-1-associated determinants recognized on fresh and mitogen-stimulated T and B cell targets. Using targets from the congenic mouse strains C57BL/6J (Qa-1b) and BS-Tlaa (Qa-1a) to demonstrate Qa-1 specificity, we found that mitogen-stimulated T and B cell blasts both expressed Qa-1 determinants. Reciprocal cold target inhibition experiments revealed that the same antigens were recognized on Con A and anti-Thy-1.2 plus C-treated LPS blasts. Furthermore, splenic and thymic Con A blasts expressed indistinguishable Qa-1-associated antigens. In a similar experiment, fresh lymphocyte targets were used to demonstrate that unstimulated splenocytes and thymocytes expressed the same antigens. Anti-Thy-1.2 plus C-treated fresh splenic B cell targets also expressed Qa-1 antigens, none of which were apparently unique, as demonstrated by inhibition of cytotoxicity by immunoglobulin-negative splenic T cells. In addition, using CBA anti-B10.BR effectors, cytotoxicity of anti-Thy-1.2 plus C-treated fresh E6-Tlaa splenic B cells was inhibited by anti-Qa-1 serum. Thus, Qa-1 determinants were expressed on resting and activated T and B lymphocyte subpopulations, and no qualitative differences were identified between determinants recognized by Qa-1-specific cytotoxic effectors on the various lymphoid subpopulations.
Abstract The Qa-11 Ag expressed in certain strains with the B2-microglobulin-b allele, apparently maps into the Tla region as well as into the Qa-2 region. Moreover Qa-11 has been shown to be biochemically indistinguishable from Qa-2. Genetic complementation studies combining the right Qa and Tla regions failed to lead to Qa-11 expression. To elucidate the molecular basis of this apparent paradox, we examined the expression of Qa-11 on products of transfected Q-region class I genes. Immunochemical analysis has shown that the Qa-11 Ag is expressed on class I molecules encoded by the Q7 gene from both C57BL/10 (Q7b) and BALB/c (Q7d), but not on the protein product of the Q9 gene isolated from the C57BL/10 strain (Q9b). Inasmuch as the predicted protein products of the Q7b and Q9b genes would differ at a single amino acid, a residue critical for Qa-11 expression has been identified. Based on these results it is proposed that among the beta-2-mb strains, the Qa-11+/Qa-2+ mice are likely to express at least the Q7 gene, whereas Qa-11-/Qa-2+ mice express only Q9. In support of this model, the Qa-2+/Q-11- recombinant B6.K2, essential for the apparent mapping of Qa-11 into the Tla region, expresses only Q9 but not Q7 encoded molecules on the cell surface, and only Q9 and no processed Q7 mRNA is detected in the cytoplasm. This expression pattern in B6.K2 cannot be explained on the basis of a single crossing-over event.
Unlike many of the topics Queue tackles, QA isn’t sexy or exciting. It isn’t new, hip, or happenin’. You’ll not see many magazine covers proclaiming QA to be the next big thing, in the vein of past cover crazes: Push Technology Will Change the World!; or XML, XML, XML!; or Java, This Changes Everything!
Radiotherapy plays a crucial role in cancer treatment. An important innovation in the delivery of treatment is the MR-linac, a device that combines magnetic resonance imaging with a linear accelerator. This system enables precise visualization of tumors and surrounding tissues before the start of the treatment session, allowing daily variations to be incorporated directly into the adapted treatment plan while the patient is on the treatment table. This approach is known as online inter-fraction adaptive radiotherapy. In addition to imaging before treatment, the MR-linac can also acquire images during radiation delivery to track tumor motion, enabling techniques such as beam gating and intra-fraction drift correction. This is known as online intra-fraction adaptive radiotherapy. To ensure the accuracy of these treatments, quality assurance (QA) procedures are performed. Some of these involve measurements with dosimeters, which quantify the delivered dose. To validate the complete workflow, end-to-end (E2E) tests are conducted that encompass all clinical steps. This thesis investigates the accuracy of measurement devices used on the MR-linac and the accuracy of MR-linac workflows. Several key conclusions were drawn from the conducted studies. First, two devices used for dose measurements, a plastic scintillation detector and a Delta4 phantom, were evaluated and shown to be capable of time-resolved dosimetry with a high temporal resolution. Next, a motion platform was characterized and assessed for use in the MR-linac, enabling the integration of motion into dosimetric measurements. Combining these devices provided a tool capable of performing dosimetry during controlled motion of the detector. After the assessment of these devices, two E2E tests were performed to evaluate the online inter- and intra-fraction adaptive workflows. For the online inter-fraction adaptive workflow, 3D gel dosimeters were employed, demonstrating excellent geometric and dosimetric accuracy and providing volumetric information not available from 1D and 2D dosimeters. To evaluate online intra-fraction adaptive workflows, a novel E2E testing approach was developed, demonstrating that motion-inclusive reference dose distributions are crucial for reliable accuracy assessment. This study demonstrates that intra-fraction adaptive treatments can be delivered with high accuracy. Finally, the feasibility of log file–based dose reconstructions during intra-fraction motion was explored. These calculations showed good agreement with measured dose distributions and hold promise as a tool for patient-specific QA of intra-fraction adaptive workflows. Overall, this thesis presents a comprehensive evaluation of measurement devices and workflows for the MR-linac. By characterizing detectors, developing motion-integrated measurement tools, and performing E2E tests of both online inter- and intra-fraction adaptive workflows, it establishes practical methods for QA and verification of treatment accuracy.
This guide to quality assurance of Open, Distance and Flexible Learning (ODFL) provision is intended to support Ministry of Education officials and teachers in the Pacific to roll out high quality distance education in their own contexts. Whilst expansion of ODFL has significantly increased participation in education, upholding the quality of provision cannot be overemphasised. The guide contains six units: (1) Understanding quality and quality assurance in ODFL; (2) Key components of quality in ODFL; (3) Implementing quality in ODFL; (4) Enhancing quality through policy; (5) ICT infrastructure and quality; and (6) optional readings. This guide was developed as part of the Partnership for Open, Distance and Flexible Learning in the Pacific Project, supported by Ministry of Foreign Affairs and Trade, New Zealand.