Step 1Place the chicken and celery in a mixing bowl.
Step 2Mix together the yogurt, sour cream, lemon juice, curry powder and cumin in a small bowl, then add to the chicken and celery. Stir well, then season with salt and pepper to taste.
Step 3Cut the pita in half to form two pockets. Line each pocket with 2 lettuce leaves. Spoon the chicken mixture into the pita halves, dividing evenly.