Isolation and cryopreservation of human peripheral blood monocytes.

A modification of the Freundlich and Avdalovic method (J. Immunol. Methods 62, 31 (1983] is reported. Buffy coats, separated and pooled together, are used for isolation of monocytes (70% yield, 100% purity). Cell density of working suspension is increased up to 0.65 X 10(9) cells/75 cm2 surface by multiplication of the active fibronectin sites. For the purpose, cryoprecipitate is used instead of plasma for coating the glass-gelatin surface. Monocytes, isolated by that procedure, could be successfully cryopreserved with dimethyl sulfoxide cryoprotective solution.

Aggregate formation in cryopreserved leukocyte suspensions.

During cryopreservation of leukocytes, a great part of the granulocytes is injured. The latter is responsible for aggregate formation in the suspension and a loss in the number of preserved cells. The formation of aggregates in the suspension is potentiated in the presence of serum in the cryoprotective medium. On the other hand, the presence of sugar (sucrose, lactose, dextrose) in the washing solution diminishes the aggregate formation, the latter effect being directly proportional to the final concentration of the sugar in the suspension. The aggregates contain mainly cells and very rarely amorphous or fibrous zones. They appear only in the presence of serum. Their formation is not connected with presence of traces of fibrinogen in the serum.

Antibodies and thermolabile opsonins in the phagocytosis of human red and white blood cells pretreated with formaldehyde.

Erythrophagocytosis is conditioned by serum immunoglobulins. The extent of phagocytosis depends on the haematocrit of the red cell suspension pretreated with formaldehyde. The higher the haematocrit value, the lower will be the extent of phagocytosis. Phagocytosis of white blood cells pretreated with formaldehyde by granulocytes and monocytes is conditioned mainly by a thermolabile fraction of the serum, probably the complement.