Explain why no precipitate formed with the diluted antibody?

you are given two solutions, one containing protein X and the other containing antibody to protein X. When you add 1 ml of anti-X to 1 ml of protein X, a precipitate forms. But when you dilute the antibody solution 100-fold and then mix 1ml of the diluted anti-X with 1 ml of protein X, no precipitate forms.