M. Geiser et al., Interaction of fungal spores with the lungs: Distribution and retention ofinhaled puffball (Calvatia excipuliformis) spores, J ALLERG CL, 106(1), 2000, pp. 92-100
Background: The biologic responses to inhaled airborne fungal spores, which
are well-known allergen carriers, would be better understood if we had an
insight into their pattern of distribution and interaction with lung struct
ures.
Objectives: To investigate the retention characteristics of inhaled basidio
spores, which often represent the major portion of the spore load in air-sa
mpling surveys and to analyze their regional distribution within and intera
ction with the lungs.
Methods: Intubated and anesthetized Syrian Golden hamsters inhaled aerosols
of puffball (Calvatia excipuliformis) spores, with an aerodynamic diameter
of 3.1 mu m, either by spontaneous breathing (group A, n = 3) or by contin
uous negative-pressure ventilation (group B, n = 4). Lungs were fixed by in
travascular perfusion of fixative solution within 29 minutes of the initial
inhalation, and tissue samples were then professed for light and electron
microscopy,
Results: Stereological (fractionator) analysis of lung tissue revealed that
the greatest number of spores was deposited within the alveoli (67.2% in g
roup A and 89.8% in group B), The intrapulmonary conducting airways retaine
d an intermediate proportion (32.3% in group A and 10.0% in group B), where
as the extrapulmonary mainstem bronchi and trachea held the lowest proporti
on (0.5% or less). Deposited spores were lodged within the aqueous lining l
ayer and in close proximity to the epithelial cells. Within the intrapulmon
ary conducting airways, 22.3% of the spores in group A and 9.0% of those in
group B had been engulfed by macrophages.
Conclusion: This study demonstrates that inhaled 3-mu m-diameter basidiospo
res become distributed over a large surface area. It also reveals that such
particles are displaced by surfactant (surface forces) into the aqueous li
ning layer of airways and alveoli, thereby facilitating subsequent phagocyt
osis by macrophages. This interaction of spores with lung structures may be
important for the development of respiratory allergies induced by airborne
fungal allergens.