Effects of activated T cells on osteoclastogenesis depend on how they are activated.
BACKGROUND
Activated T cells are emerging as important regulators of osteoclast function in inflammatory diseases. Both pro- and anti-resorptive properties have been described. We reasoned that this reported variability of the effects of T cells on osteoclast formation depends on how T cells are activated in vitro.


METHODS
We harvested T lymphocytes from 5-week-old C57BL/6 mouse spleens. Activation was performed with anti-CD3epsilon and -CD28 Ab (Abs), concanavalin A (Con A), phytohemagglutinin (PHA), or the superantigen Staphylococcal enterotoxin A (SEA). Osteoclastogenesis was induced by receptor activator of NF-kappaB ligand (RANKL) in the mouse macrophage cell line RAW 264.7 cells, or primary macrophage CD11b+ cells from mouse spleen. Cells were cultured with T cells or with their conditioned medium.


RESULTS
Co-culture of activated T lymphocytes with RAW 264.7 cells inhibited osteoclastogenesis but only when activated by Abs. This effect was CD4+ -dependent. Conditioned medium from activated T lymphocytes with Abs consistently blocked osteoclastogenesis in RAW 264.7 and CD11b+ cells. T cells activated with SEA, Con A, and PHA had inconsistent effects on osteoclastogenesis. We then tested the role of interferon (IFN)-gamma, a known inhibitor of osteoclastogenesis, in the effects of T cells on osteoclast formation. IFN-gamma neutralizing antibody blocked the inhibitory effect of T-cell conditioned medium on osteoclastogenesis. Osteoclast precursors from IFN-gamma receptor-null mice treated with 0.1% medium from activated T cells formed osteoclasts. However, higher doses of medium inhibited osteoclastogenesis, so that we cannot exclude that other factors besides IFN-gamma may be involved.


CONCLUSIONS
Available methods to activate T lymphocytes result in variable effects on osteoclastogenesis. IFN-gamma is the main factor responsible for the inhibitory effects of activated T cells on osteoclast formation.
Wyzga
Nancy
N
Connecticut Children's Medical Center, Hartford, CT, USA.
Varghese
Samuel
S
Wikel
Stephen
S
Canalis
Ernesto
E
Sylvester
Francisco A
FA
D000818:Animals; D002454:Cell Differentiation / Q000502:physiology*; D002460:Cell Line; D016207:Cytokines / Q000494:pharmacology / Q000502:physiology; D008213:Lymphocyte Activation / Q000187:drug effects / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D010010:Osteoclasts / Q000166:cytology* / Q000187:drug effects / Q000502:physiology; D013601:T-Lymphocytes / Q000166:cytology* / Q000187:drug effects / Q000502:physiology
D016207:Cytokines