IL1B and osteonecrosis: Moreover, in the presence of alendronate, osteoclast progenitor cells were converted to TNFα-, IL-6- and IL-1β-expressing cells in vitro, and blocking TNFα, either by gene targeting or treatment with the TNFα-inhibitor etanercept, significantly inhibited osteonecrosis development, even in alendronate-treated mice with infectious osteomyelitis mice.