Here's why:

* Antibodies: Antibodies are specialized proteins produced by the immune system. They bind to specific antigens (foreign substances like bacteria, viruses, or toxins), marking them for destruction by other immune cells.

* Immune Cells: Immune cells, like lymphocytes, are packed with proteins that help identify and destroy invaders. For example, T-cells have receptors that recognize and bind to infected cells, leading to their destruction.

* Enzymes: Many enzymes, which are also proteins, play vital roles in immune responses. They break down pathogens, activate immune cells, and help repair damaged tissues.

While other macromolecules like carbohydrates and lipids have indirect roles in immunity, proteins are the key players in fighting off diseases.