Ultrastructural study of leucocytes and urates in gouty arthritis.

Abstract

Exudative leucocytes and associated urate crystals found in 18 synovia from 11 patients with gouty arthritis were studied by light, polarizing, and electron microscopy. The cytopopulation consisted mainly of emigrated neutrophils. Varying numbers of mononuclear leucocytes were present and the phagocytic macro-phages contained pyknotic neutrophils, shed cytoplasmic buds of neutrophils, and urate crystals. The morphological appearance of urate crystals in ultrathin sections and their characteristics during electron bombardment were investigated. In ultrathin sections the majority of urate crystals contained within the cytoplasm particularly of neutrophils, were devoid of a limiting membrane and appeared to lie free within the cytoplasmic matrix. Other intraleucocyte urate crystals were outlined by a dense line which was either continuous or interrupted at intervals. Rarely was a urate crystal found in a typical phagosome. The cytoplasm of certain other neutrophils in synovia from each patients with gout revealed a striking "honeycombed" appearance. This mottled effect was evident because the more dense cytoplasmic matrix was separated by electronlucent spaces. These spaces varied in size and shape, were not membrane-bounded and contained widely dispersed particles of low electron density. Neutrophils in gouty arthritis contain accumulations of a low-density material and urate crystals which are devoid of a membrane may suggest that the urate crystals are formed at an intracellular site.