Larry is taking a walk in the park. the pollen in the air makes him sneeze constantly. what line of defense is his immune system exhibiting?

His immune system is using the first line of defense. His body is using purging methods that is caused by irritation of the hairs in his nose. This defense system uses physical and chemical barriers that are prepared to defend the body from infection.

It is the first line of defense because when the pollen goes on the person, the human skin acts like an chemical barrier which protects it from. 

Blood transfusions were rarely done and often fatal; they were outlawed until the nineteenth century.