Temperature effects on shape and function of human granulocytes

Scanning microscopic and functional studies were made of granulocytes isolated from CPD anticoagulated whole blood by counterflow centrifugation in a Beckman JE-6 rotor. The collection buffer was phosphate (20 mM) buffered saline (280 mOsM) with glucose (29 mM) and human serum albumin (1.2% w/v). The final suspension contained less than 2% mononuclear cells and 5% red cells. Incubation and fixation at various temperatures revealed two distinct temperature dependent shape transformations. At 22, 37, 40 and 45 degrees C granulocytes were ameboid with extensive highly textured veils. These smoothed progressively, bullae and blebs formed, and membranes peeled finally leaving nonfunctional spheres with smooth surfaces. At 4 degrees C, granulocytes were irregular spheres, less rugose but with numerous microvilli and nodules. Veiling was absent. Phagocytosis, initially low, progressively declined over 48 h while cell surfaces become smooth. Some formed blebs, but all terminated as nonfunctional spheres with untextured surfaces containing occasional large single holes. Cellular stability estimated from changes in volume distributions, and phagocytosis by microfluorescence measurements of yeast and latex particle ingestion were also temperature dependent and paralleled the shape progressions. It is concluded that at body (37 degrees C) or fever (40 degrees C) temperatures, granulocytes have dynamic membrane surfaces characterized by extensive veiling and high function. At 4 degrees C they are relatively inactive spheres devoid of pseudopodia or veils, yet functional at slow rates.