Am. J. Respir. Crit. Care Med.,
Volume 158, Number 1, July 1998, 263-269
Immunization and Challenge with Toluene Diisocyanate
Decrease Tachykinin and Calcitonin Gene-Related
Peptide Immunoreactivity in Guinea Pig
Central Airways
CRISTINA E.
MAPP,
ROSARIA E.
LUCCHINI,
DEBORAH
MIOTTO,
PASQUALE
CHITANO,
LAURA
JOVINE,
MARINA
SAETTA,
PIERO
MAESTRELLI,
DAVID R.
SPRINGALL,
JULIA
POLAK,
and
LEONARDO M.
FABBRI
Institute of Occupational Medicine, University of Padova, Padova; and Institute of Infectious and Respiratory Diseases, University of Ferrara,
Ferrara, Italy; Department of Histochemistry, Royal Postgraduate Medical School, University of London, London, United Kingdom
Toluene diisocyanate (TDI) is a potent sensitizer that causes occupational asthma in a significant proportion of subjects exposed. We used an animal model to investigate whether neuropeptide changes
occur in the airways of immunized and TDI-challenged guinea pigs. Animals were immunized by
weekly intradermal injections, challenged with TDI (5 to 20 ppb) after the third injection, and killed 6 h
after exposure. Control guinea pigs received injections of saline. Lung tissue was processed immediately and analyzed for nerves using the streptavidin-biotin complex peroxidase method with antisera
to the neural marker protein gene product 9.5 (PGP 9.5), substance P (SP), and calcitonin gene-
related peptide (CGRP). We also quantified the inflammatory infiltrate in the submucosa of central
airways, and we measured the serum level of specific IgG and IgG1. Specific antibodies against TDI
were present only in immunized animals. Immunized as compared with nonimmunized animals had a
significant increase in eosinophils in the submucosa of central airways, and a further increase was observed 6 h after TDI challenge. Immunization and TDI challenge did not modify the number of mononuclear cells in the submucosa of central airways in both nonimmunized and immunized animals. TDI
exposure did not change the overall innervation in both nonimmunized and immunized animals, but
the density of PGP 9.5-positive nerves was significantly different between nonimmunized and immunized TDI-challenged animals. The density of SP-, and CGRP-immunostained nerves was significantly lower in immunized TDI-challenged than in nonimmunized animals. TDI exposure significantly decreased the density of SP-positive nerves in nonimmunized animals. A negative relationship was
found between the presence of airway inflammation, as indexed by eosinophil cell infiltration, and
the density of PGP 9.5-, SP-, and CGRP-immunostained nerves. In conclusion, TDI produces airway inflammation and neuropeptides changes in the central airways of immunized guinea pigs 6 h after TDI challenge. These findings support an interaction between tachykinins, inflammatory (i.e., eosinophils) and possibly immune cells.
