Germinal Center Dendritic Cells Express More ICAM-1 Than Extrafollicular Dendritic Cells and ICAM-1/LFA-1 Interactions are Involved in the Capacity of Dendritic Cells to Induce PBMCs Proliferation

Jean-Jacques Goval ¹, Roland Greimers ¹, Jacques Boniver ¹ and Laurence de Leval ^1*

¹ Department of Pathology, University of Liege, CHU of Liege, Liege, Belgium

^* To whom correspondence should be addressed. E-mail: L.deLeval{at}ulg.ac.be.

	Abstract

Germinal center dendritic cells (GCDCs) have been identified as CD11c⁺ CD4⁺ CD3^- cells located in GCs with the ability of inducing marked proliferation of allogenic T-cells. Using immunofluoresence techniques, we have observed that this CD11c⁺ CD4⁺ CD3^- immunophenotype identified GCDCs but also a subset of extrafollicular DCs. By flow cytometry, we were able to discriminate the GCDCs (CD11c^high CD4^high lin^-) from the other tonsil DCs. By immunofluorescence and flow cytometry, we found that dendritic cells of germinal centers express more ICAM-1 (CD54) than extrafollicular dendritic cells. Proliferation of peripheral blood mononuclear cells (PBMCs) induced by coculture with purified CD11c⁺ CD4⁺ CD3^- DCs was reduced by addition of blocking anti-CD54 antibodies. In summary, distinct levels of ICAM-1 expression allow the distinction between GCDCs and extrafollicular DCs, and cellular interactions mediated by CD54 are likely to play a role in the capacity of GCDC to stimulate allogenic PBMCs proliferation.

Key Words: germinal center dendritic cells, human tonsils, ICAM-1, CD54, immunofluorescence, flow cytometry

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