"Tolerization" of human T-helper cell clones by chronic exposure to alloantigen

Induction of clonal anergy in T-helper (Th) cells may have a role in regulating immune responses. A model system for studying Th cell tolerization at the clonal level in vitro could be useful for investigating the mechanisms involved. Accordingly, alloreactive helper cells were maintained in culture with interleukin 2 (IL 2) by intermittent stimulation with specific antigen. Regardless of the frequency of antigen stimulation, clones of age less than ca. 35 population doublings (PD) were found to undergo antigen-specific autocrine clonal expansion in the absence of exogenous IL 2. Such young clones (designated as phase I) could therefore not be "tolerized" by frequent exposure to antigen. In contrast, most clones of age greater than ca. 35 PD could be tolerized by frequent exposure to antigen (designated as phase II clones). Their autocrine proliferation was then blocked, although they still recognized antigen specifically as shown by their retained ability to secrete interferon-gamma (IFN-gamma) and granulocyte-macrophage colony stimulating factor (GM-CSF). The mechanism of response failure involved both an inability to upregulate IL 2 receptors in the absence of exogenous IL 2, as well as an inability to secrete IL 2. These defects were not overcome by stimulation with mitogens or calcium ionophore and phorbol esther in place of alloantigen. T-cell receptor, alpha, beta, and gamma-chain gene rearrangements remained identical in phase I and phase II clones. Tolerization of phase II clones could be avoided by increasing the period between antigen exposures. Despite this, whether or not phase II cells were capable of autocrine proliferation, they were found to have acquired the novel function of inducing suppressive activity in fresh lymphocytes. Suppressor-induction was blocked by the broadly reactive MHC class II-specific monoclonal antibody (moAb) TU39, but not by moAb preferentially reacting only with HLA-DR, DQ, or DP. Sequential immunoprecipitation on T-cell clones showed the presence of a putative non-DR, DQ, DP, TU39+ molecule on phase II clones. However, this molecule was also found on phase I clones. The nature of the TU39-blockable suppressor-inducing determinant present on phase II but not on (most) phase I clones thus remains to be clarified. In addition to suppressor-induction activity, phase II clones also acquired lytic potential as measured in a lectin approximation system. Cytotoxic (CTX) potential was also not influenced by the frequency of antigenic stimulation and could be viewed as a constitutive modulation of clonal functio

SYNTHESIS, INTRACELLULAR DISTRIBUTION, AND SECRETION OF IMMUNOGLOBULIN AND H-2 ANTIGEN IN MURINE SPLENOCYTES

A/J spleen cells were labeled with [3H]leucine and at intervals thereafter were homogenized and separated into microsomes and cell sap. Ig and H-2 antigens were assayed in the cell fractions and cell supernatants using immunoprecipitation. In addition, cells labeled by enzymatic radioiodination were incubated to determine the rates of release of Ig and H-2 antigens from the surface. The results indicate that the majority of Ig and H-2 antigens remain membrane bound throughout their intracellular life. In contrast to Ig, H-2 antigens are neither secreted nor shed from the cell surface. It is suggested that Ig is a peripheral protein of the cell membrane, whereas H-2 antigens are integral ones. The release of Ig on a fragment of plasma membrane could occur at fixed cell surface areas that contain no H-2 antigens or from which they have migrated before release

Time resolved X ray absorption spectroscopy of infrared laser induced temperature jumps in liquid water

A time resolved X ray absorption study of the structural dynamics of liquid water on a picosecond timescale is presented. We apply femtosecond midinfrared pulses to resonantly excite the intramolecular O H stretching band of liquid water and monitor the transient response in the oxygen K edge absorption spectrum with picosecond X ray pulses. In this way, structural changes in the hydrogen bond network of liquid water upon an ultrafast temperature jump of approximately 20 K are investigated. The changes of the X ray absorption as induced by such a temperature jump are about 3.2 . This demonstrates that our method serves as a sensitive probe of transient structural changes in liquid water and that combined infrared laser synchrotron experiments with substantially shorter X ray pulses, such as generated with a femtosecond slicing scheme, are possibl

Synaptic targets of photoreceptors specialized to detect color and skylight polarization in Drosophila

Color and polarization provide complementary information about the world and are detected by specialized photoreceptors. However, the downstream neural circuits that process these distinct modalities are incompletely understood in any animal. Using electron microscopy, we have systematically reconstructed the synaptic targets of the photoreceptors specialized to detect color and skylight polarization in Drosophila, and we have used light microscopy to confirm many of our findings. We identified known and novel downstream targets that are selective for different wavelengths or polarized light, and followed their projections to other areas in the optic lobes and the central brain. Our results revealed many synapses along the photoreceptor axons between brain regions, new pathways in the optic lobes, and spatially segregated projections to central brain regions. Strikingly, photoreceptors in the polarization-sensitive dorsal rim area target fewer cell types, and lack strong connections to the lobula, a neuropil involved in color processing. Our reconstruction identifies shared wiring and modality-specific specializations for color and polarization vision, and provides a comprehensive view of the first steps of the pathways processing color and polarized light inputs

Amplitude measurements of Faraday waves

A light reflection technique is used to measure quantitatively the surface elevation of Faraday waves. The performed measurements cover a wide parameter range of driving frequencies and sample viscosities. In the capillary wave regime the bifurcation diagrams exhibit a frequency independent scaling proportional to the wavelength. We also provide numerical simulations of the full Navier-Stokes equations, which are in quantitative agreement up to supercritical drive amplitudes of 20%. The validity of an existing perturbation analysis is found to be limited to 2.5% overcriticaly.Comment: 7 figure

X-ray Raman scattering study of aligned polyfluorene

We present a non-resonant inelastic x-ray scattering study at the carbon K-edge on aligned poly[9,9-bis(2-ethylhexyl)-fluorene-2,7-diyl] and show that the x-ray Raman scattering technique can be used as a practical alternative to x-ray absorption measurements. We demonstrate that this novel method can be applied to studies on aligned $\pi$-conjugated polymers complementing diffraction and optical studies. Combining the experimental data and a very recently proposed theoretical scheme we demonstrate a unique property of x-ray Raman scattering by performing the symmetry decomposition on the density of unoccupied electronic states into $s$- and $p$-type symmetry contributions.Comment: 19 pages, 8 figure

Partial characterization of Ia antigens from murine lymphoid cells

Congenic anti-Ia antisera were used to bind radiolabelled Ia antigens from cells of various strains of mice of known H-2 haplotype. The results indicate that Ia antigens are proteins of molecular weight 30,000 to 35,000 daltons. The Ia antigens are distinct from known H-2 antigens as judged by independent immunoprecipitation as well as by molecular weight. Ia antigens are synthesized by, and are present on the surface of lymphoid cells as evidenced by incorporation studies using 3 H-leucine and enzymatic radioiodination of cells, respectively. Tissue distribution of cell surface Ia suggests that Ia antigens are on B cells. Ia antigens were detected in the incubation media of 3 H-leucine labeled splenocytes suggesting that antigens may be secreted.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46728/1/251_2005_Article_BF01564048.pd