Put mayonnaise in a large bowl and stir in the lemon juice. Set aside. Halve and core the apples, but do not peel them; chop into bite-size cubes.
Add the apples to mayonnaise dressing and stir until the pieces are well coated. Add celery, walnuts and raisins into the bowl and mix gently.
Arrange the lettuce leaves on a large serving plate and spoon the salad onto the center.