Immunity Crossword

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Across
  1. 3. type of immunity humans are born with
  2. 5. used to help people gain immunity artificially
Down
  1. 1. substance recognised by immune cells, leads to a reaction
  2. 2. one of cells that activates lymphocytes, looks similar to neurons
  3. 4. caused by overactive immune system
  4. 6. produced by type B lymphocytes