It has been clinically observed that several neoplasms including leukemia mysteriously show spontaneous regression after severe feverish infection and inflammation.35, 36 As ULMW-HA is abundantly secreted from mesenchymal cells at the site of infection and inflammation,37 it may directly act as one of cell death-inducing factors for tumors expressing CD44 at high levels. This evidence concerns the gene CD44 and infection.