Functional involvement of E-cadherin in TGF-beta 1-induced cell cluster formation of in vitro developing human langerhans-type dendritic cells

Epithelial Langerhans cells (LC) represent immature dendritic cells that re quire TGF-beta 1 stimulation for their development. Little is known about t he mechanisms regulating LC generation from their precursor cells. We demon strate here that LC development from human CD34(+) hemopoietic progenitor c ells in response to TGF-beta 1 costimulation (basic cytokine combination GM -CSF plus TNF-alpha, stem cell factor, and Flt3 ligand) is associated with pronounced cell cluster formation of developing LC precursor cells. This ce ll-clustering phenomenon requires hemopoietic progenitor cell differentiati on, since it is first seen on day 4 after culture initiation of CD34(+) cel ls, Cell cluster formation morphologically indicates progenitor cell develo pment along the LC pathway, because parallel cultures set up in the absence of exogenous TGF-beta 1 fail to form cell clusters and predominantly give rise to monocyte, but not LC, development (CD1a(-), lysozyme(+), CD14(+)). TGF-beta 1 costimulation of CD34(+) cells induces neoexpression of the homo philic adhesion molecule E-cadherin in the absence of the E-cadherin hetero ligand CD103, Addition of anti-E-cadherin mAb or mAbs to any of the constit utively expressed adhesion molecule (CD99, CD31, LFA-1, or CD18) to TGP-bet a 1-supplemented progenitor cell cultures inhibits LC precursor cell cluste r formation, and this effect is, with the exception of anti-E-cadherin mAb, associated with inhibition of LC generation. Addition of anti-E-cadherin m Ab to the culture allows cell cluster-independent generation of LC from CD3 4(+) cells. Thus, functional E-cadherin expression and homotypic cell clust er formation represent a regular response of LC precursor cells to TGF-beta 1 stimulation, and cytoadhesive interactions may modulate LC differentiati on from hemopoietic progenitor cells.