Key adhesion molecules are present on long podia extended by hematopoieticcells

Background: We recently reported that CD34(+) hematopoietic cells and the K G1a cell line extend long, thin podia. These podia can dynamically extend a nd retract, often adhere to the substrate, and appear to connect cells up t o 300 mu m apart. The surface receptors found on these podia have not been described. Methods: By using time-lapse fluorescent microscoscopy and immunostaining t echniques, we describe a method for detecting surface receptors on these po dia. This includes an in situ antibody staining procedure without fixing ce lls. Results: We demonstrate, using CD34 selected mobilized peripheral blood cel ls and KG1a cells, that adhesion molecules known to play important roles in blood-cell migration and adhesion are present on these podia. These includ e: CD11a, CD18, CD29, CD34, CD45, CD49d, CD49e, and CD62L. Additionally, CD 54 and CD44 tr:ere present on the podia extended by KG1a cells, but mere no t detectable on the primary CD34(+) cells. The integrin CD49d localized at the base of these podia in a time-dependent manner in KGla cells. The frequ ency and morphology of these long podia on three myeloid leukemia-cell line s (KG1a, MV4-11, and AML-193) and a CD34-negative T-cell line (CEM) are als o compared. KGla and CEM cell lines extend long, dynamic podia that are sim ilar to the podia on primary CD34(+) cells in morphology and adhesion molec ule expression. The AML-193 and MV4-11 cell lines, however, did not extend these long podia. Conclusions: We describe a technique that provides a method of detecting su rface receptors on thin cell membrane projections. These results support th e likely role of these podia in cell migration and cell-cell communication. Cytometry 37:171-177, 1999. (C) 1999 Wiley-Liss, Inc.