In contrast to adherent cells, cells growing in suspension in up to 30% of transfected human primary T lymphocytes. and particularly hematopoietic cells, are notoriously difficultFlow cytometry analysis performed on T lymphocyte subto transfect in vitro using nonviral approaches. In the sets revealed that 8 and 9%, respectively, of CD4 and CD8 present study, the effect of cell adhesion on gene transfer cells could be transfected with a plasmid carrying the green efficacy was investigated by allowing hematopoietic cells fluorescent protein gene. Other adherent cells, such as to bind to an adherent cell monolayer (ACM) before being MS5 murine stromal cells or HeLa epithelial cells, were subjected to cationic liposome-mediated DNA transfer. also a compatible matrix for AAL. Moreover, the pCMV␤ Human CD34 and T CD4 cell lines were cultivated on an plasmid was present in similar amounts in the nuclei of TF1 ACM constituted of murine fibroblast NIH3T3 cells and cells transfected in suspension or with the AAL procedure. transfected with a plasmid carrying the ␤-galactosidase These data raise the possibility that cell matrix/ gene. X-gal staining showed that up to 27% of the cells hematopoietic cell interactions might govern expression of expressed the transgene. In contrast, less than 0.1% of the transgene in hematopoietic cells growing usually in these cells were positively transfected in suspension. This suspension, but not endocytosis of liposome/DNA particles adhesion-assisted lipofection (AAL) procedure was also and plasmid migration to the cell nucleus. successfully tested on blood lymphocytes, since it resulted