Osteopontin is involved in the initiation of cutaneous contact hypersensitivity by inducing Langerhans and dendritic cell migration to lymph nodes.

Osteopontin (OPN) is a chemotactic protein that attracts immune cells, to inflammatory sites. The sensitization phase of allergic cutaneous contact hypersensitivity (CHS) requires the migration of Langerhans cells/dendritic cells (LCs/DCs) from skin to draining lymph nodes. Characterizing OPN function for LC/DC migration we found upregulated OPN expression in hapten sensitized skin and draining lymph nodes. OPN induces chemotactic LC/DC migration, initiates their emigration from the epidermis, and attracts LCs/DCs to draining lymph nodes by interacting with CD44 and alphav integrin. Furthermore, OPN-deficient mice have a significantly reduced CHS response that correlates with an impaired ability of OPN-deficient mice to attract LCs/DCs to draining lymph nodes. In conclusion, OPN is an important factor in the initiation of CHS by guiding LCs/DCs from skin into lymphatic organs.

Real-time interactive virtual endoscopy of the tracheo-bronchial system: influence of CT imaging protocols and observer ability.

OBJECTIVE: To evaluate the influence of different spiral CT examination protocols suitable for clinical use on image quality and to assess the observer dependence in interactive real-time virtual bronchoscopy. METHODS AND PATIENTS: Real-time perspective volume rendering of the airways in twenty normal patients based on four different spiral CT examination protocols was evaluated by four observers in regard to the order of depictable bronchi. RESULTS: Best results were obtained using an examination protocol with a small beam collimation and a maximum pitch. Depending on the observer's ability to control the fly path and the orientation of the bronchi with respect to the slice plane up to sixth order bronchi could be depicted. Inter-observer variability was up to two branching orders. CONCLUSION: The performance of virtual bronchoscopy strongly depends on the applied CT examination protocol and the observers experience with perspective volume rendering. Both of which have to be taken into account when virtual bronchoscopy is compared with fiberoptic bronchoscopy.

Estimation of the frequency of self-reactive T cells in health and inflammatory diseases by limiting dilution analysis and single cell cloning.

Autoreactive T cells have recently been detected not only in autoimmune diseases but also in healthy individuals, but their frequency is thought to be low. The aim of our study was to estimate the frequency of self-reactive T cells by using limiting dilution analyses of peripheral blood lymphocytes. Assessment of self-reactivity in this study was defined as T-cell proliferation to autologous non-T cells in the absence of foreign antigens. When culture conditions were optimized by adding interleukin 2, healthy individuals showed a frequency of self-reactive T cells ranging from 1/60 to 1/600. These results were confirmed by using unseparated peripheral blood leukocytes or Epstein-Barr virus transformed B-cell blasts as stimulators. All cultures were performed exclusively in autologous serum. Single cell cloning from a healthy donor yielded 568 T-cell clones, 12 of which showed self-reactivity giving a frequency of more than 1 in 50 T cells. Eight of these 12 T-cell clones were inhibited by MHC-class II antibodies. Frequency analyses of self-reactive T cells in patients with autoimmune diseases (rheumatoid arthritis, autoimmune hepatitis or primary biliary cirrhosis), with viral hepatitis or with inflammatory bowel diseases showed similar frequencies in all patient groups and no significant differences from normal individuals. In conclusion, we have found a high frequency of self-reactive T cells in both health and disease. We postulate that self-reactive T cells constitute an important part of the physiological T-cell repertoire.