Multinucleated giant cells generation induced by interferon-gamma. Changes in the expression and distribution of the intercellular adhesion molecule-1 during macrophages fusion and multinucleated giant cell formation.
BACKGROUND
Multinucleated giant cells (MGC), interferon-gamma (IFN-gamma) production, and increased expression of adhesion molecules are features of granulomatous reactions. IFN-gamma induces the fusion of macrophages and the subsequent MGC generation in vitro. Moreover, IFN-gamma increases ICAM-1 expression on lymphoid cells and an important role for adhesion molecules in MGC generation has been proposed.


METHODS
The time course of the IFN-gamma-driven MGC generation was investigated in slide-chamber cultures of adherence-purified human monocytes. The fusion index, the monocytes clustering the total number of MGC were determined. The expression of intercellular cell adhesion molecule-1 (ICAM-1), LFA-1 and HLA-DR was investigated by immunohistochemistry. The effect of anti-ICAM-1, anti-LFA-1 and anti-HLA-DR monoclonal antibodies on IFN-gamma-induced MGC generation was also examined.


RESULTS
IFN-gamma enhanced the generation of MGC in a dose- and time-dependent fashion. In all experiments, MGC formation was preceded by a sequence of changes in the morphology of cultured monocytes. Cell clustering occurred as early as 3 days after IFN-gamma stimulation and was followed by the adhesion of cells that eventually fused. Immunohistochemistry showed that ICAM-1 was increased by IFN-gamma and constantly polarized on a cell uropode. When monocytes clustered, ICAM-1 was localized on the membrane where the cell-to-cell contact occurred. In newly formed MGC, ICAM-1 stained in the center of the giant cell. The cellular distribution of LFA-1 on cultured monocytes was not modified by IFN-gamma. HLA-DR expectedly enhanced by IFN-gamma was mostly cytoplasmic and tended to disappear when MGC formed. Finally, anti-LFA-1 and anti-ICAM-1 monoclonal antibodies variably inhibited IFN-gamma-induced MGC generation.


CONCLUSIONS
Taken together, these data add support to the concept that IFN-gamma is essential for MGC generation by promoting cell clustering and cell-to-cell adhesion. The present data also indicate that among the mechanisms by which IFN-gamma exert such a promoting effect, changes in the ICAM-1 expression and cellular distribution are included. The observation that ICAM-1 appears to be trapped in the cytoplasm of IFN-gamma-driven MGC and that HLA-DR tend to disappear from macrophages undergoing MGC formation, also suggest changes in the functional properties of these cells.
Istituti di Clinica Medica 2, Virologia, di Anatomia Patologica 2 Universita' La Sapienza, Roma, Italy.
S
S
Fais
V L
VL
Burgio
M
M
Silvestri
M R
MR
Capobianchi
A
A
Pacchiarotti
F
F
Pallone
D002459:Cell Fusion; D015743:Giant Cells, Foreign-Body / Q000166:cytology* / Q000378:metabolism; D006684:HLA-DR Antigens / Q000378:metabolism; D006801:Humans; D007124:Immunoenzyme Techniques; D066298:In Vitro Techniques; D018799:Intercellular Adhesion Molecule-1 / Q000378:metabolism*; D007371:Interferon-gamma / Q000494:pharmacology*; D016169:Lymphocyte Function-Associated Antigen-1 / Q000378:metabolism; D008264:Macrophages / Q000166:cytology* / Q000378:metabolism
D006684:HLA-DR Antigens; D016169:Lymphocyte Function-Associated Antigen-1; D018799:Intercellular Adhesion Molecule-1; D007371:Interferon-gamma