A full Stokes vector ellipsometry measurement system for in situ diagnostics in dynamic experiments.

A fast ellipsometry system with a resolution of only a few nanoseconds that can simultaneously measure all four Stokes parameters was developed for use in dynamic experiments. Due to its fine temporal resolution, the system is useful for a wide variety of dynamic setups, two of which are presented, fast foil heating and shock compression. As a test case the optical properties of nickel were measured in a fast foil heating setup. The complex index of refraction and emissivity at 532 nm and in the range of 1000-1900 K are presented. It was found that the emissivity monotonously increases below and above the melting point while an abrupt increase of about 2% was observed at the phase transition. These results are in accordance with the literature. Shock compression experiments included sample-free surface measurements. Samples of 1020 steel were shocked up to 25 GPa on the Hugoniot curve. The measured optical properties under these conditions showed a significant change; the value of the emissivity was doubled.

High pressure ellipsometry: a novel method for measuring the optical properties and electronic structure of materials in diamond anvil cells.

High pressure ellipsometry (HPE) method was developed for determining the index of refraction of opaque materials in a diamond anvil cell (DAC). A main difficulty in DAC-based HPE, namely, the pressure-induced birefringence developed in the diamond, was overcome enabling the extraction of the ellipsometric parameters of the sample. The method used was based on the fact that an unpolarized light is unaffected by a retarding optical element and thus reduces the number of unknown parameters in the problem. Because of technical difficulties in using unpolarized light, a linear combination of orthogonal polarizations was applied. In the experimental procedure, multiangle measurements of the ellipsometric parameter ψ are collected at each pressure and the data is fitted together with a measurement of the near normal reflectivity, in order to extract the complex index of refraction. As a test case, this procedure was used to measure the high pressure index of refraction of iron up to 30 GPa for light with wavelengths of 532 and 633 nm. From the index of refraction as a function of pressure the diamond-iron interface emissivity for different pressures was derived and from which the phase transition α → ε could be identified and characterized. The emissivity increases with pressure both at the α (0-9 GPa) and the ε phase (21-30 GPa) however decreases at the mixed α - ε (9-21 GPa) range. From the imaginary part of the index of refraction the pressure dependence of the energy skin depth of iron was extracted. It was found that the energy skin depth increases by an order of magnitude at 30 GPa relative to ambient conditions.

In vitro IgM and IgM rheumatoid factor production in response to Staphylococcus aureus Cowan I: evidence for the role of Leu-2-positive T suppressor cells and radiosensitive T helper cells.

Staphylococcus aureus Cowan I (SAC) is a potent stimulus of B cell proliferation and differentiation, the latter being T cell-dependent. It has been suggested that immunoglobulin and IgM rheumatoid factor (RF) production in response to SAC involves radiosensitive T helper cells. We studied normal peripheral blood mononuclear cell (PBMC) cultures to assess the roles of radiosensitive T cells and Leu-2 positive suppressor cells in the cellular control of SAC-stimulated IgM and IgM RF responses. Depletion of Leu-2 positive T cells from reconstituted autologous PBMC cultures resulted in an increase in SAC-stimulated IgM production in the majority of individuals, implying the involvement of Leu-2 positive suppressor T cells in this system. Suppression by Leu-2 positive cells is less evident in the SAC-induced IgM RF response, suggesting qualitative differences between IgM and IgM RF SAC-stimulated responses in PBMC cultures from the same normal individuals. Irradiation (1000 rads) of the T cell-enriched subpopulation, either with or without Leu-2 positive cell depletion, resulted in statistically significant decreases in IgM and IgM RF production in response to SAC in reconstituted autologous cultures, providing further evidence of a Leu-2 negative radiosensitive sheep-cell rosetting cell active in in vitro SAC responses. In contrast, PWM-stimulated PBMC cultures showed almost exclusively increases in total IgM and IgM RF production when T cells were irradiated (1000 rads) before culture, consistent with the radiosensitive T suppressor cell involved in the in vitro immunoglobulin responses to PWM. The same five out of nine individuals produced IgM RF, under different culture conditions, in response to PWM and SAC, suggesting that the ability of an individual to produce IgM RF lies intrinsically within the B cell.

IgE-mediated allergy to peanut, cow's milk, and egg in children with special reference to maternal diet.

Nineteen children with IgE-mediated allergy associated with strongly positive prick skin tests and RASTs to peanut or cow's milk and/or egg were studied. Seventeen of the children had been breast fed, ten had been exclusively breast fed for a minimum of 5 months. Reactions to these foods occurred on first exposure to the food in all but one instance, suggesting that in 18 instances sensitization had occurred antenatally or via the breast. A retrospective inquiry indicated that most of the mothers had had a generous intake of the food(s) to which their children were sensitized, but mothers of sensitized children did not consume more of these foods than the mothers of non-sensitized children; moreover, avoidance of the foods (peanut in two instances and egg in one) did not ensure freedom from sensitization to peanut and/or egg. Breast feeding by itself cannot be guaranteed to protect against the development of food allergy.

Development of a reverse enzymoallergosorbent test (REAST) to detect timothy-specific IgE antibodies. Comparison with RAST.

Radioallergosorbent test (RAST) for the measurement of IgE antibodies has been introduced more than 15 years ago and a number of technical modifications have since improved its sensitivity and reproducibility. The test has been applied to the diagnosis of allergy and to determine changes in the levels of IgE antibodies following immunotherapy. However, specific IgG antibodies are raised during such a therapy and can interfere with the RAST. We have developed a reverse enzymoallergosorbent test (REAST) where microtiter plates are first coated with a purified polyclonal anti-IgE antibody, then with the serum to test and finally with peroxidase-labeled antigen. This assay is antigen specific as shown by the significant inhibition of binding of the labeled antigen in presence of unlabeled specific antigen (greater than 95%) and the absence of inhibition in presence of irrelevant antigens. The values found in atopic patients (85 subjects) were significantly higher than in the non-atopic donors (35 subjects) (1.14 U +/- 1.20 vs. 0.01 U +/- 0.02, P less than 0.0005) and there was a good correlation with the Pharmacia RAST (P less than 0.0005). The levels of specific IgE by both REAST and RAST correlated well with the clinical symptomatology.

A study on IgE antibody-producing cells from the peripheral blood lymphocytes of atopic patients.

In the present study, the peripheral blood lymphocytes (PBL) of six rye-grass and 22 ragweed atopic patients demonstrated secretion of IgE antibody from 7-day cultures as measured by a sensitive ultra-low RAST. The RAST binding ranged from 1.5% to 21% whereas the cell supernatants from the PBL of eight non-atopic individuals showed little or no response (1.2%). The addition of antigens (rye grass 1 or AgE) or interleukin (IL-2) to the cultures on day 0 failed to cause an increase in response. But examination of PBL from four of these patients by a reverse hemolytic plaque assay showed that challenge of these cells by antigen or IL-2 caused an increase in the number of antigen-specific IgE plaque forming cells. The bulk of the IgE antibody secreting cells were located in a sheep red blood cell rosetted fraction (cell fraction 2) whereas most of IgE antibody PFC were found in the non-rosetting fraction (cell fraction 1). It appears that the reverse hemolytic plaque assay detects IgE antibody-producing cells which can still undergo immune regulation and may represent an earlier stage of B cell differentiation whereas the ultra-low RAST appears to measure spontaneous plasmablast cell IgE antibody response.

Detection of antigen-specific IgE-plaque-forming cells from peripheral-blood lymphocytes of ragweed- and grass-allergic patients.

The reverse haemolytic plaque assay was developed to measure antigen (AgE or rye grass I)-specific IgE-plaque-forming cells from the peripheral-blood lymphocytes of ragweed- and grass-allergic patients. The anti-IgE-developing antisera was shown to be isotype-specific, and the response of the assay was inhibited by 52% by the addition of 10 pg of antigen. In addition, the assay was shown to have a reproducibility (s.d.) of 15%. The blood lymphocytes from all fifteen atopic (grass and ragweed) patients were shown to form antigen-specific IgE-plaque-forming cells during the pollen season (mean value 115 cells) and up to 6 months after the season (mean value 56 cells). Cycloheximide appears to block the formation of the plaque-forming cells. This method appears to be sensitive and reproducible enough to study in vitro IgE antibody synthesis of peripheral-blood lymphocytes from atopics.

Effect of antigen stimulation on antigen-specific IgE-plaque-forming cells from peripheral-blood lymphocytes of atopics.

In the present study, it was shown that allergen challenge in vitro produced an increase in the number of antigen-specific IgE-plaque-forming cells of peripheral-blood lymphocytes from grass- or ragweed-allergic patients. Thus, the blood lymphocytes of all twelve (four rye grass I and eight AgE) sensitive donors responded whereas the blood lymphocytes of five non-atopic controls were unresponsive to antigen challenge. Allergen challenge doses of 10(-10)-10(-12) g/ml were found to give the greatest number of plaque-forming cells whereas the number of plaque-forming cells at challenging doses between 10(-9) and 10(-7) g/ml were either the same or less than those obtained with unchallenged cells. The results are discussed as to whether this in vitro model system represents in vivo response to allergen of the allergic patient.

The regulatory effect of histamine on the immune response: III. Defect on in vitro IgE production in atopics.

Spontaneous in vitro production of IgE was found higher in a group of untreated grass sensitive atopic patients than in normal volunteers when assessed at the cellular level with a reverse hemolytic plaque assay. This study also confirmed the increase of IgE synthesis after pokeweed mitogen stimulation in non-atopic donors and its decrease in atopic patients. Moreover, in this work we looked for a potential defect in immunoregulatory functions in atopic patients toward the in vitro IgE production. Indeed, histamine is known to activate suppressor cells capable, in turn, of suppressing IgG and IgE production from normal cells. In atopic patients, histamine could activate cells capable of suppressing IgG production but not IgE. Furthermore, similar findings were found when Concanavalin A-induced suppressor cells were examined. These findings suggest (a) a defective regulatory function towards IgE in atopic patients and (b) that the same subpopulation of suppressor cells seems to be activated by histamine and ConA and defective in atopic patients.

IgG4: non-IgE mediated atopic disease.

This review article attempts to define the role of IgG4 in allergic disease. Evidence from the literature suggests that IgG4 antibodies may act as sensitizing as well as blocking antibodies. The mechanism(s) of the dual properties of this immunoglobulin sub-class in this disease is discussed in relation to the various immunopharmacologic (target cell) and immunological (lymphocyte) pathways. It is clear that availability of IgG4 myelomas and the development of monoclonal antibodies to IgG4 is essential for further research in this area. Preliminary findings suggest that IgG4 antibodies may be important in certain types of food allergic reactions. More work should be done to analyze pediatric populations for IgG4-RAST to a variety of food allergens.