Plasma cells in human gingiva: An electron microscope study

The fine structure of plasma cells in clinically healthy human gingiva has been investigated. The cytoplasm was occupied by a profuse rough endoplasmic reticulum, consisting of parallel and circular arrays of cisternae, which contained a moderately dense, flocculant material. Attached to the cisternal membranes were ribosomal configurations in spirals or coils. Round and elongated mitochondria were distributed in a perinuclear fashion and possessed cristae with sharp angulations along their membranes. A well developed Golgi complex was situated in the cytocentrum adjacent to the nucleus and consisted of three major elements: smoothmembraned saccules with characteristic terminal expansions, vacuoles, and dispersed vesicles. These elements frequently contained material of considerable electron‐opacity. Transitional elements (see text) were observed on the endoplasmic reticulum immediately adjacent to the Golgi complex, and evaginations or “blebs” occurred at variable points along their membranes. Cytoplasmic dense bodies in various stages of development were intimately associated with the Golgi. Small forms were membrane‐bound and contained a fine, dense, granular material. Large bodies were also limited by a unit membrane and demonstrated a crystalline internal structure with a major and minor periodicity of about 100 Å. Russell bodies, as described by previous investigators, were not encountered. It is suggested that the dense bodies are formed by the Golgi complex, and may represent lysosomes or non‐hydrolytic enzyme storage units.