Which cells are responsible for the defense of the body?

Leukocytes, commonly known as white blood cells, are crucial components of the immune system and are responsible for defending the body against infections and foreign invaders. These cells play various roles in recognizing, attacking, and eliminating pathogens such as bacteria, viruses, and parasites. There are several types of leukocytes, including neutrophils, lymphocytes, monocytes, eosinophils, and basophils, each with specific functions that contribute to the body's immune response.

Erythrocytes are primarily responsible for transporting oxygen throughout the body but do not participate in immune defense. Thrombocytes, or platelets, play a key role in blood clotting and wound healing, but they do not have a role in fighting infections. Fibroblasts are connective tissue cells involved in the repair and formation of tissues, but they do not function in the immune response. Thus, among the provided options, leukocytes are the clear leaders in defending the body against disease and maintaining health.