CRYOPRESERVATION OF CYTOLOGICAL SPECIMENS FOR IMMUNOCYTOCHEMISTRY

A method has been established for storage and preservation of cytological specimens in liquid nitrogen and further processing for immunocytochemistry as smears prepared from thawed cells or cryo-sections of frozen cell pellets. For the experiments cultured cells of a T-lymphoblastic leukemia cell line (ATCC CCL 119) and blood cells of the buffy coat of healthy humans were treated with a cryo-solution (fetal calf serum +5 % dimethylsulfoxid) and after freezing stored in liquid nitrogen. Alternatively, cells preincubated with cryo-solution followed by suspension in fetal calf serum without cryo-additive were frozen and stored in liquid nitrogen for the production of cryo-sections. Indirect immunofluorescence and alkaline phosphatase - antialkaline phosphatase based immunoreactions were performed for the decoration of various surface antigens with a panel of monoclonal antibodies. All immunoreactions were repeated at least three times and the stored cell preparations were investigated after different periods of storage (up to four months). The immunoreactions of fresh cells in suspension (which were used as controls) were comparable with those of cryopreserved cells, e.g. cells on smears after thawing and on cryo-sections of cell pellets. The strongest immunoreactions were achieved on fixed cryo-sections. The maintenance of cell morphology of smears from cryopreserved cells was slightly better than of cells from cryo-sections. In our bands the preparation of cell pellets, which are suitable for the storage in liquid nitrogen and the production of cryosections, is a very useful method for immunocytochemical investigations of cytological specimens especially in situations where immunoreactions cannot be performed on fresh material. Moreover, it provides a possibility for repetition or modification of the immunohistochemical reactions for the same cell population.