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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 αv 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.

Analysis of measurements of the static scattering function by electron and X-ray diffraction, ofthedynamicscatteringlaw hyneutronscattering,andofinfraredand Raman spectrapointsattheimportant role of twin helix-reversal defects for the molecular dynamics in the intermediate phase and high-temperature phase (modifications IV and I) of poly(tetrafluoroethy1ene). In contrast to single helix-reversal defects, these twin defects constitute a local perturbation which can move along the chain without affecting remote units. One species, the 'coherent" twin defect, possesses a particularly low formation energy, since it retains the twist long-range order along the chain. Formation of the defects occurs mainly in the intermediate phase.In the high-temperature phase a saturation is observed. The steep increase in the defect concentration in the intermediate phase followed by the equilibration in the high-temperature phase can he understood as a transition between a disordered State controlled by intra-and intermolecular forces to one which is only determined by the intramolecular potentials. In spite of the disorder in the helices, an orientational shortrange order is retained for sequences in adjacent chains. The degree of order is related to the defect concentration. The reorientation of the C h group resulting from the formation and motion of the twin defects occurs with rates in the range of 10-100 GHz. Orientational shorbrange order leads to a slowing down.

Perfluoro-n-eicosane (n-C 2o F 42 ) passes through three different solid modifications, called M(T < 146 K), 1(146 < T <200 K), and R( T> 200 K). Structures of the phases M and R were characterized by x-ray scattering experiments. Crystals are built up by rectangular layers. In modification M layers are set up by arrays of right-handed and left-handed (15/7-) helices in alternate succession. The unit cell is monoclinic (a = 9.65 A, b = 5.70 A, c = 28.3 A, and /3 = 97"; space group Pa). In modification R molecules are highly mobile. There is no ordering with regard to the helix handedness. Molecules resemble cylindrical objects and are packed in a hexagonal dense mode. Regular layer stacking results in crystals with rhombohedral symmetry (a = b = 5.70 A, c = 85.00 A, r = 120°; space group R 3m).

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