Specific polyclonal and monoclonal antibody prevents paraquat accumulation into rat lung slices.

Sheep polyclonal and mouse monoclonal antibodies have been produced that bind to the bipyridyl herbicide, paraquat. The binding capacities and affinities of the various antibody solutions (serum, ascites, purified tissue culture supernatant) to paraquat were determined using a radioimmunoassay. All antibody solutions bound paraquat with high affinity (Ka = 10(9)-10(10) l/mol). The sheep polyclonal antisera, the mouse ascites fluid, and the purified culture supernatant had mean binding capacities of 8, 1 and 22 micrograms paraquat/ml respectively. All the antibody preparations were able to prevent the in vitro accumulation of paraquat into rat lung tissue. The amount of antibody to achieve this was dependent upon the binding capacity of the antibody solution, i.e. when the binding capacity of the antibody was equal to the amount of paraquat present in the incubation medium a total blockade of uptake was achieved. When antibody was added to lung tissue that had been accumulating paraquat for 1 hr, the inhibition of uptake was immediate and was complete for at least 2 hr. Both the radioimmunoassay and lung slice experiments indicate that an equivalent of 1 mg of IgG is required to bind 2.5 micrograms of paraquat ion. Preincubation of lung tissue with antibody did not affect the subsequent accumulation of paraquat, nor did it result in a detectable degree of intracellular neutralisation of paraquat as measured by paraquat's ability to stimulate the pentose phosphate pathway. The rate of efflux of paraquat from lung slices prepared from rats dosed intravenously with paraquat was not increased by the presence of antibody in the incubation medium. In conclusion, neutralising antibodies to paraquat have been produced. They bind to paraquat in solution with high affinity and render the paraquat unavailable for its in vitro accumulation into lung cells.

Influence of chronic low-level exposure to lead on plasma immunoglobulin concentration and cellular immune function in man.

The immunological status of individuals occupationally exposed to low levels of inorganic lead has been examined and compared with that of non-exposed, age and sex-matched controls. At the time of testing the exposed population had a mean (+/- SD) blood lead concentration of 38.4 +/- 5.6 micrograms X 100 ml-1 (n = 39) compared with a mean value of 11.8 +/- 2.2 micrograms X 100 ml-1 (n = 21) for the control group. No differences in the serum concentrations of IgG, IgA and IgM between the populations were observed and there existed no correlation between blood lead concentration and serum immunoglobulin levels. In addition assessment was made of the capacity of peripheral blood mononuclear cells to respond to the mitogen phytohaemagglutinin (PHA), a correlate of T cell function, and to spontaneously lyse cells of the erythroleukaemic cell line K562, a measure of NK cell function. In neither case was there a difference between exposed and control populations and no correlation between reactivity and blood lead concentration. Although previous studies in rodents have indicated that exposure to inorganic lead resulting in similar blood lead concentrations may compromise immune competence our data suggest that no similar effect occurs in man.

Allergy to laboratory animals: a retrospective and a prospective study.

Twenty four volunteers who had been allergic to laboratory animals for some years were examined by means of a questionnaire paying particular attention to symptoms associated with rats and by serological and skin tests with extracts of rat urine (retrospective study). Nasal and eye symptoms were reported by 21 and 16 individuals respectively: 13 had asthma. Positive skin tests and high levels of specific IgE antibody to rat urine extract were found in 17 of the more severely affected individuals and this group included 12 of those with asthma. Latent periods of work with animals before symptoms appeared varied from 0.5 to 12 years. Also 148 individuals were studied during their first year of work with animals (prospective study). Symptoms developing during the year were reported by 15%, asthma by 2%. IgE antibody levels to rat urine were raised in 40% of affected and 6% of the unaffected individuals but there was no significant correlation between symptoms and either antibody levels or positive skin tests. Allergic symptoms developing during the first year of postemployment were, on the whole, much milder than those seen in the retrospective study. A tentative conclusion is that most individuals who become allergic to laboratory animals develop the condition in a mild form during their first year of employment but it appears probable that atopic individuals, although having an equal chance of developing allergy as compared with non-atopic individuals, may eventually progress to a more severe form of the disease.

Enzyme linked immunosorbent assay (ELISA) for paraquat.

An Enzyme Linked Immunosorbent Assay (ELISA) has been developed for the estimation of paraquat. The amount of paraquat present in samples of human plasma was estimated in terms of the degree to which it combined with a rabbit antibody raised to a conjugate to paraquat with bovine serum albumin. The amount of residual, uncombined, antibody after being allowed to react with a conjugate of paraquat with keyhole-limpet haemocyanin bound to the surface of a polystyrene micro-titre plate, was estimated by the addition of an enzyme-labelled anti-rabbit IgG, followed after washing by addition of substrate and subsequent determination of optical density. Concentrations of paraquat in the range 0.3-10 ng/ml could be measured and the antibody showed a high degree of specificity. Results correlated well with those of a widely-validated radio-immunoassay but the ELISA was simpler and more sensitive.