Mix the cheese, shrimp, green onions, and celery in a bowl. Mix well. Add mayonnaise and stir until combined. Preheat broiler. Generously spread shrimp mixture on bread slices, covering edges.
Arrange on baking sheet and broil for 4 minutes or until golden brown and bubbly. Serve at once. You may prepare the shrimp mixture up to one day in advance and store, covered, in refrigerator. Makes about 30 toasts.