Cross-recognition of a mouse H-2-peptide complex by human HLA-restricted cytotoxic T cells

Epstein-Barr virus (EBV)-specific human cytotoxic T lymphocyte (CTL) lines from a virus-immune HLA-A11+ donor CMc produced significant lysis of transfected mouse P815 target cells (H-2d background) expressing an introduced HLA-A11 heavy chain gene and the EBV gene encoding latent membrane protein (LMP). To identify the target epitope being recognized, HLA-A11+ transfectants of P815/A11) were pre-exposed to synthetic peptides corresponding to fragments of the LMP sequence and the cells then tested for lysis by CMc effectors; untransfected P815 parent cells were included in these assays as control recipients of the same peptides. Unexpectedly, we identified a peptide preparation (corresponding to LMP residues 124-137) which specifically sensitized not only P815/A11 cells but also the parental P815 cells to lysis. Four independent anti-EBV CTL lines derived from donor CMc gave the same result and single-cell cloning confirmed that lysis was mediated by a subset of the HLA-A11-restricted EBV-specific CTL clones which dominate CMc effector populations. Two lines of evidence indicated that peptide presentation to the human CTL was occurring through H-2Kd molecules on the surface of P815/A11 and P815 cells: (a) a monoclonal antibody reactive with H-2Kd specifically blocked the lysis of both P815/A11 and P815 peptide-treated targets, and (b) on an extended target cell panel, peptide-mediated sensitization was also obtained with a second H-2d mouse line A20.2J and with an H-2Kd transfectant of the H-2k line R1E. This work has therefore identified EBV-specific HLA-A11-restricted human CTL which show fortuitous cross-recognition of a synthetic peptide in the context of a mouse H-2Kd molecule. Such potential for xenogeneic cross-reactivity needs to be borne in mind in situations where the target specificity of human CTL is being analyzed on HLA gene-transfected murine target lines.

Elimination of "hook-effect" in two-site immunoradiometric assays by kinetic rate analysis

Two-site or sandwich immunoradiometric assays (IRMAs) offer theoretical advantages over competitive immunoassay systems for sensitivity, precision, and rapid incubation. The practical realization of these advantages has been limited by the phenomenon of the "high-dose hook effect," such that high concentrations of an analyte give similar responses to those of much lower concentrations. We have developed a kinetic rate monitoring IRMA system for use with the Kineti-Count 48TM, an automated kinetic radioassay analyzer, which eliminates "hook-effect" interference, thereby permitting optimal assay design for increasing sensitivity and reducing incubation time. Practical illustration of these concepts is demonstrated by a 10-min, automated, quantitative assay we developed for human choriogonadotropin. The assay can detect as little as 1.2 int. units/L and kinetically screens for the hook effect. Kinetic rate analysis of the two-site IRMA and potentially of nonisotopic counterparts permits improvements in the speed and reliability of these immunoassays.

Elimination of "hook-effect" in two-site immunoradiometric assays by kinetic rate analysis

Two-site or sandwich immunoradiometric assays (IRMAs) offer theoretical advantages over competitive immunoassay systems for sensitivity, precision, and rapid incubation. The practical realization of these advantages has been limited by the phenomenon of the "high-dose hook effect," such that high concentrations of an analyte give similar responses to those of much lower concentrations. We have developed a kinetic rate monitoring IRMA system for use with the Kineti-Count 48TM, an automated kinetic radioassay analyzer, which eliminates "hook-effect" interference, thereby permitting optimal assay design for increasing sensitivity and reducing incubation time. Practical illustration of these concepts is demonstrated by a 10-min, automated, quantitative assay we developed for human choriogonadotropin. The assay can detect as little as 1.2 int. units/L and kinetically screens for the hook effect. Kinetic rate analysis of the two-site IRMA and potentially of nonisotopic counterparts permits improvements in the speed and reliability of these immunoassays.

A comparison of growth inhibition of Tetrahymena furgasoni by C19 and C21 steroids

The growth inhibition of Tetrahymena furgasoni (once known as "T. pyriformis W") by C19 and C21 steroids of similar structure was measured by determining cell population at 24 h and 48 h following addition of the steroid. A cis-fusion of the A/B rings junction, unsaturation at C-1,2, or C-4,5 and carbonyl substitution all enhanced inhibition, whereas the presence of two hydroxyl groups decreased inhibition. The results indicated that the transformation of C19 and C21 steroids by this protozoon may be part of a detoxication mechanism.

Deep Methane Maxima in the Northwest Caribbean Sea: Possible Seepage Along the Jamaica Ridge

Methane concentrations as great as 30,000 nanoliters per liter were measured on two cruises in the northwest Caribbean Sea. Such concentrations are three orders of magnitude higher than Bunsen solubilities would predict. Although shallow maxima may result from in situ microbial activity, the deeper maxima appear to result from massive seepage (estimated at 1 x 10(8) to 10 x 10(8) liters per day) along the Jamaica Ridge.