Altered sensitivity to cholchicine and PHA in human cultured cells.

PHA-stimulated lymphocytes cultivated from a pair of human monozygotic twins yielded mostly tetraploid cells when colchicine was not used to arrest the metaphases. The rate of tetraploidy was also enhanced by colchicine in fibroblasts cultured without PHA. In in situ condition, larger than usual cells were observed. Other defects found in parental lymphocyte cultures included C-anaphase cells and increased cell aggregation. These results suggest a membrane mutation resulting in hypersensitivity to PHA and variant response to colchicine.