Patch testing with p-toluene diamine preparations of different ages.

Analyses of the stability of 1% p-toluene diamine (PTD) in petrolatum used for patch testing showed a rapid decline of the PTD concentration down to 0.1%, possibly due to the generation of dye complexes. To study whether the diagnostic quality of this test preparation is compromised by the chemical reactions taken place, a multicentre study was conducted by the German Contact Dermatitis Research Group (DKG), comparing patch test results in 177 patients with simultaneously tested PTD preparations of different ages. During the 10-month course of this study, the age of the batches ranged from 2 to 11 months for batch A, from 7 to 16 months for batch B and from 11 to 20 months for batch C. There were no statistically significant differences between reactions to batches A and B, A and C, and B and C. Agreement of patch test reactions to the 3 batches was very good and comparable to the general reproducibility of patch test with standard allergens. The chemical reactions mentioned above apparently do not affect the diagnostic quality of PTD patch test preparations because the true allergen probably is not PTD itself, but one or more of the reaction products.

Evaluation of a commercially available ELISA kit as a tool to determine BTEX in groundwater.

The reliability of enzyme-linked immunosorbent assay (ELISA) tests as a screening technique to address groundwater contamination was tested in an area following leakage of gasoline from a petrol station. Immunoassay data of benzene, toluene, ethylbenzene, and o-, m- and p-xylene (BTEX) were compared with results obtained using capillary gas chromatographic analysis. Detection limits were of 20 microg l(-1) for ELISA and 0.3 microg l(-1) for gas chromatography with flame ionization and photoionization detectors (GC-FID/PID) determination. Despite an observed overestimation of BTEX concentrations as given by ELISA, the tests responded reliably to different levels of contamination.

Immunological and in-vivo neurological studies on a benzoic acid-specific T cell-derived antigen-binding molecule from the serum of a toluene-sensitive patient.

T-cell-derived antigen-binding molecules (TABMs) specific for benzoic acid were isolated from the serum of a toluene-sensitive patient. The resulting purified TABMs (BA-TABMs) did not contain immunoglobulin G and were associated with the cytokine transforming growth factor-beta (TGF-beta). BA-TABMs bound to benzoic acid conjugated to human serum albumin (BA-HSA), as well as to other chemicals conjugated to human serum albumin-including dinitrophenol and oxazolone. The binding of BA-TABMs to the conjugated chemicals increased the level of detectable TGF-beta, and a similar effect was observed with the unconjugated chemicals, benzoic acid and 2,4-dinitrophenol glycine. The increase in TGF-beta was critically dependent on the ratio between BA-TABMs and the conjugated or unconjugated chemicals; the increase was optimum at intermediate concentrations and absent at low and high concentrations. The authors used an established animal model in vivo and demonstrated that TGF-beta enhanced the inflammatory response induced by the release of neuropeptides from sensory nerves; this enhancement occurred in a dose-dependent manner. The BA-TABMs also enhanced this neurogenic inflammatory response in a dose-dependent manner, and this effect was blocked by anti-TGF-beta antibody. When the authors added either BA-HSA or benzoic acid, the effect of BA-TABMs on neurogenic inflammation was further enhanced at intermediate concentrations of antigen and was unaltered or reduced at higher concentrations. TABMs specific to particular chemicals, as a result of their association with cytokines (e.g., TGF-beta), may be implicated in symptom production in chemically sensitive patients.

Detection of antigen-specific human serum proteins related to the T-cell receptor in infectious disease and in an immune response to milk proteins or chemicals.

A monoclonal IgG2 antibody, MG3C9-1 A12, was prepared by immunization of mice with human serum Cohn Fraction III proteins enriched for TCR Ca+ proteins. MG3C9-1 A12 bound to Mr 28,000, antigen-specific TCR Ca+, beta-, and TCR Ca+, beta+ serum proteins associated with TGF-beta1, 2. The IgG2 monoclonal antibody also bound to T-lymphocyte proteins but did not bind to B lymphocyte proteins, human albumin, IgM, IgG, IgA, or TGF-beta1, 2, 3 immunogenic peptides. Monoclonal MG3C9-1 A12 detected TCR-related proteins specific for filarial extract, milk proteins, or benzoic acid in the sera of individuals with chronic or asymptomatic filariasis, milk intolerance, or sensitivity to toluene, respectively. TCR-related serum proteins were also detected intracellularly in mononuclear cells in frozen sections of ileum from a patient with milk intolerance and reactive mesenteric lymph nodes from a patient with a gastric ulcer. The results suggest that antigen-specific TCR-related serum proteins may be elevated during an immune response to oral, environmental, or infectious stimuli.

Clinical and immunological responses in subjects sensitive to solvents.

Twenty patients proved sensitive to a 15-min exposure to 15 ppm toluene. We assessed patients neuropsychologically before and after toluene exposure, and they had impaired cognitive functioning characterized by a deterioration in short- and long-term memory and psychomotor coordination. We measured total immunoglobin G and T-cell antigen-binding molecules against an antigen prepared by conjugation of para-aminobenzoic acid to human serum albumin in 20 patients and 16 controls. There was no significant difference in the immunoglobulin G levels to the antigen in the 2 groups, but the levels of T-cell antigen-binding molecules against the para-aminobenzoic acid conjugated to human serum albumin were elevated significantly in subjects sensitive to toluene. We also found significant associations between T-cell antigen-binding molecule levels and (a) decreased performance on the STROOP (Colour Word) test, (b) a shift in focal length following toluene exposure, (c) clinical assessment of disability, and (d) longer histories of chemical exposure. The measurement of T-cell antigen-binding molecules against chemical haptens may be valuable in the assessment of patients who are sensitive to chemicals.

Efficacy of skin barrier creams (I). The repetitive irritation test (RIT) in the guinea pig.

An animal model for the evaluation of skin protective creams against chemical irritants is described. The irritants were applied daily for 2 weeks to shaved back skin of young guinea pigs: sodium lauryl sulphate (5% aq.; 30 min), sodium hydroxide (0.5% aq.; 2 min), and toluene (20% eth.; 2 min). The barrier cream was applied 2 h prior to and immediately after exposure to the irritant. Control animals were treated with the irritant only. The irritant reaction was scored on a 4-point scale for erythema and quantified with regard to transepidermal water loss (TEWL) by evaporimetry and skin blood flow volume (BFV) by laser Doppler velocimetry. A total of 90 guinea pigs, consisting of individual panels of 5 to 10 animals, was tested. While one barrier cream (Stokoderm) significantly suppressed the irritation due to sodium lauryl sulphate and toluene, the other (Contra-Alkali) failed to do so and even aggravated the response, which was particularly evident with sodium hydroxide. This model may be useful in developing more effective barrier creams.

Antigens which detect IgE antibodies in workers sensitive to toluene diisocyanate.

Two antigens, both containing tolyl groups, were compared for ability to detect IgE antibodies in workers hypersensitive to toluene diisocyanate. One antigen, formed by reaction of p-tolyl isocyanate with human serum albumin, detected antibodies in each of ten hypersensitive workers. A second tolyl antigen, formed by reaction of p-toluoyl chloride and human serum albumin, and therefore lacking isocyanate linkages, detected antibodies in seven of the ten workers. In RAST assays, sera from toluene diisocyanate-sensitive workers demonstrated higher binding to human serum albumin-coated control discs than did sera from non-sensitive workers. The significance of this binding in calculating tolyl-reactive antibody titres is discussed.