Crossword puzzle

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Across
  1. 1. What is the body’s largest physical barrier against infection?
  2. 4. What is the approximate percent of people worldwide who have allergies?
  3. 5. What is sent through the body’s vessels to transport nutrients and oxygen?
Down
  1. 2. What type of immunity acts as the body’s built-in, first response?
  2. 3. Which line of defense responds specifically to antigens?