Ultrastructural alterations and phagocytic function of cryopreserved platelets.

Fresh human platelets and platelets cryopreserved in 4% dimethylsulfoxide were examined ultrastructurally before and after incubation in a suspension of latex particles. Cryopreserved platelets had fewer discoid forms than fresh platelets. The cryopreserved platelets had many sphered platelets containing an increased number of vacuoles; the sphered platelets were more electron-lucent margination and pallor of organelles. Phagocytosis of latex into vacuoles was markedly impaired in the cryopreserved platelets. The morphologic alterations suggested that the freezing, thawing, and washing procedures reduced the functional activity of platelets.