IL4 and periodontitis: In addition, it was reported that IL-4 is able to downregulate pro-inflammatory cytokines149 and restrain osteoclastogenesis.3 On the other hand, Th2 cells also support the destructive B cell response,150,151 and the infiltration of abundant B cells and plasma cells, a sign of type II immunity, was observed in progressed periodontitis.151 This inconsistency in data and results has driven investigators to search for other hidden mechanisms to explain the mode of periodontitis pathogenesis.