TAK1 phosphorylates IKK-beta (Wang et al. 2001). As inferred from chicken B cells, the reaction in human B cells may occur when TAK1 and the IKK complex are associated with the CARMA1:BCL10:MALT1 (CBM) complex. During T cell activation TAK1 forms a complex with TAB1 and TAB2, which binds K-63 conjugated polyubiquitin attached to TRAF6 associated with the CBM complex (Sun et al. 2004, reviewed in Shinohara et al. 2009). TRAF6 also polyubiquitinates IKK-gamma in T cells (Zhou et al. 2004). B cells contain functional TRAF6 and TRAF2 (Zhang et al. 2010) so the same mechanism may occur during activation of B cells.