CD44 and pneumonia: Pharmaceutically pure HA does not bind to CSF-1 BMDM macrophages and has no CD44-mediated interaction. Pharmaceutically pure HA binds to CSF-2 BMDM macrophages indirectly by CD44, but does not cause the production of TNF-α, IL-12, CD40, CD86, IL-1β. Splenic macrophages F4/80+ also bind pharmaceutically pure HA, but splenic DCs do not. Binding of HA with macrophages does not lead to the production of TNF-α, IL-12, CD40, CD86, IL-1β. Pharmaceutically pure HA does not cause pneumonia.