Continuous Blood Sampling in Small Animal Positron Emission Tomography/Computed Tomography Enables the Measurement of the Arterial Input Function.

For quantitative analysis and bio-kinetic modeling of positron emission tomography/computed tomography (PET/CT) data, the determination of the temporal blood time-activity concentration also known as arterial input function (AIF) is a key point, especially for the characterization of animal disease models and the introduction of newly developed radiotracers. The knowledge of radiotracer availability in the blood helps to interpret PET/CT-derived data of tissue activity. For this purpose, online blood sampling during the PET/CT imaging is advisable to measure the AIF. In contrast to manual blood sampling and image-derived approaches, continuous online blood sampling has several advantages. Besides the minimized blood loss, there is an improved resolution and a superior accuracy for the blood activity measurement. However, the major drawback of online blood sampling is the costly and time-consuming preparation to catheterize the femoral vessels of the animal. Here, we describe an easy and complete workflow for catheterization and continuous blood sampling during small animal PET/CT imaging and compared it to manual blood sampling and an image-derived approach. Using this highly-standardized workflow, the determination of the fluorodeoxyglucose ([18F]FDG) AIF is demonstrated. Further, this procedure can be applied to any radiotracer in combination with different animal models to create fundamental knowledge of tracer kinetic and model characteristics. This allows a more precise evaluation of the behavior of pharmaceuticals, both for diagnostic and therapeutic approaches in the preclinical research of oncological, neurodegenerative and myocardial diseases.

The shaping of a polyvalent and highly individual T-cell repertoire in the bone marrow of breast cancer patients.

We analyzed the T-cell repertoires from the bone marrow of 39 primary operated breast cancer patients and 11 healthy female donors for the presence and frequencies of spontaneously induced effector/memory T lymphocytes with peptide-HLA-A2-restricted reactivity against 10 breast tumor-associated antigens (TAA) and 3 normal breast tissue-associated antigens by short-term IFN-gamma enzyme-linked immunospot (ELISpot) analysis. Sixty-seven percent of the patients recognized TAAs with a mean frequency of 144 TAA reactive cells per 10(6) T cells. These patients recognized simultaneously an average of 47% of the tested TAAs. The T-cell repertoire was highly polyvalent and exhibited pronounced interindividual differences in the pattern of TAAs recognized by each patient. Strong differences of reactivity were noticed between TAAs, ranging from 100% recognition of prostate-specific antigen(p141-149) to only 25% recognition of MUC1(p12-20) or Her-2/neu(p369-377). In comparison with TAAs, reactivity to normal breast tissue-associated antigens was lower with respect to the proportions of responding patients (30%) and recognized antigens (27%), with a mean frequency of only 85/10(6) T cells. Healthy individuals also contained TAA-reactive T cells but this repertoire was more restricted and the frequencies were in the same range as T cells reacting to normal breast tissue-associated antigens. Our data show a highly individual T-cell repertoire for recognition of TAAs in breast cancer patients. This has potential relevance for T-cell immune diagnostics, for tumor vaccine design, and for predicting immune responsiveness.