For example, during intracerebral hemorrhage, hemoglobin from the hematoma can activate macrophages via Toll like receptor 2 (TLR2)/Toll like receptor 4(TLR4) heterodimer, which can secrete IL-23 to induce γδ T cells to produce IL-17 to aggravate secondary damage (124). Here, TLR4 is linked to intracerebral hemorrhage.