Inhibition of human antigen-specific T cell proliferation by anti-T blast sera.

Two antisera, one raised against activated human T lymphoblasts and one raised against the human T cell line HPB-ALL, have the ability to inhibit antigen-induced T cell proliferation. Antiproliferative activity is absorbed by T blasts and HPB-ALL cells, but not by B lymphoblastoid cell lines, alpha-ethylisothiouronium bromide-treated sheep red blood cell (AET-SRBC) receptor-negative lymphoid cells, or the T cell lines MOLT-4 and HSB. The effects of these antisera do not require the presence of complement and are not attributable to toxicity during culture. The F(ab')2 fragment of anti-T blast antiserum is also active.

Invited review article: technology for attosecond science.

We describe a complete technological system at Imperial College London for Attosecond Science studies. The system comprises a few-cycle, carrier envelope phase stabilized laser source which delivers sub 4 fs pulses to a vibration-isolated attosecond vacuum beamline. The beamline is used for the generation of isolated attosecond pulses in the extreme ultraviolet (XUV) at kilohertz repetition rates through laser-driven high harmonic generation in gas targets. The beamline incorporates: interferometers for producing pulse sequences for pump-probe studies; the facility to spectrally and spatially filter the harmonic radiation; an in-line spatially resolving XUV spectrometer; and a photoelectron spectroscopy chamber in which attosecond streaking is used to characterize the attosecond pulses. We discuss the technology and techniques behind the development of our complete system and summarize its performance. This versatile apparatus has enabled a number of new experimental investigations which we briefly describe.

Probing proton dynamics in molecules on an attosecond time scale.

We demonstrate a technique that uses high-order harmonic generation in molecules to probe nuclear dynamics and structural rearrangement on a subfemtosecond time scale. The chirped nature of the electron wavepacket produced by laser ionization in a strong field gives rise to a similar chirp in the photons emitted upon electron-ion recombination. Use of this chirp in the emitted light allows information about nuclear dynamics to be gained with 100-attosecond temporal resolution, from excitation by an 8-femtosecond pulse, in a single laser shot. Measurements on molecular hydrogen and deuterium agreed well with calculations of ultrafast nuclear dynamics in the H2+ molecule, confirming the validity of the method. We then measured harmonic spectra from CH4 and CD4 to demonstrate a few-femtosecond time scale for the onset of proton rearrangement in methane upon ionization.

Functional properties of continuously cultured human T lymphocytes.

Human T lymphocytes (CCTC) have been maintained in continuous culture by a new method. The ability of CCTC to produce three types of T cell response has been determined and compared to the published responses of T cells grown in 'T cell growth factor' (TCGF) medium. Unlike TCGF cells, CCTC will not give proliferative responses when stimulated with PHA, Con A, or allogeneic lymphocytes even when supplemented with autologous PBL as a source of accessory cells. Instead, CCTC are potent inhibitors of the proliferative response of normal cells in MLC. This suppressive activity is not specific for histocompatible cells. Finally, CCTC express cytotoxic activity to a number of human lymphoid cell lines and this activity appears to be different from the polyclonal cytotoxicity reported for TCGF-maintained cells. Our method of long-term T cell culture therefore appears to grow cells with different properties from TCGF cells.