What is the term for white blood cells that play a significant role in the immune response?

Leukocytes, or white blood cells, are crucial components of the immune system, serving as the body's defense against infections and foreign invaders. They are involved in recognizing and responding to pathogens such as bacteria, viruses, and parasites. There are several types of leukocytes, each with specific functions, including lymphocytes, neutrophils, monocytes, eosinophils, and basophils. These cells can migrate to sites of infection or inflammation, where they can help neutralize harmful agents, clear debris, and stimulate other immune responses.

In contrast, thrombocytes and platelets both refer to components involved in blood clotting rather than immune responses, while erythrocytes, or red blood cells, are responsible for transporting oxygen throughout the body. Thus, leukocytes are distinctly characterized by their role in immunity, making them the correct answer to the question.