Phagocytosis by cells of the pulmonary alveoli. Transformation of crystalline particles.

The progressive transformation of illite crystals in alveolar macrophages has been studied with x-ray microanalysis and electron microdiffraction. Illite particles captured by macrophages undergo a series of progressive modifications which affect their ultrastructure, crystalline state, and chemical composition. Crystalline structure progressively disappears and certain elements are eliminated. At the end of the experiment, which lasted more than 6 months, the initial characteristics of the particles were greatly transformed. The constitutive elements of the illite particles were also found in structures other than macrophages: Type I pneumocytes, interstitium, and blood platelets.