Pharmaceutically pure HA binds to macrophages indirectly by CD44, but does not cause the production of TNF-α, IL-12, CD40, CD86, IL-1β. 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. Here, CD40 is linked to susceptibility to pneumonia measurement.