Cultured cell lines prepared by novel dual-freeze cryoembedded method mimic frozen tissue blocks in maintaining complement components

Abstract

Antibody products must be evaluated on relevant tissues, which can often be rare, difficult, and expensive to obtain. Cell lines can offer an optimal solution, and so a method to mimic frozen tissue blocks with cryoembedded cultured cell pellets was developed. Kidney sections from a patient with systemic lupus erythematosus (SLE) in the flare state were compared to cultured, cryoembedded Raji cells by detecting the complement components C1q, C3, and C4 on slides from both. An immunocytochemical (ICC) assay to detect C1q, C3, and C4 immune complexes on the Raji cell membranes was developed. The slides from the cryoembedded Raji cells were acceptable compared to the SLE kidney tissue for 99% of the C1q staining, 90% of the C3 staining, and 91% of the C4 staining. The method was also tested with a mixture of Raji cells and SW480 colorectal adenocarcinoma cells, and found that antibody staining the complement components was acceptable in the cell mixture and that the SW480 cells had acceptable staining with anti-MSH2 antibody. Further, BT-474 breast cancer cells were stained and prepared by a cryoembedding method with an anti-HER-2/neu antibody and, again, acceptable staining was observed. The method preserves cellular morphology, antigenicity, and cell-to-cell contact while avoiding freeze artifacts and the issues that arise from fixing cells, such as antigen masking and auto-fluorescence. The method to prepare cryoembedded tissue blocks that mimic frozen tissue blocks is widely applicable to the field of cytopathology.