Which of the following blood components is directly involved in the immune response?

White blood cells are crucial to the immune response, as they play a key role in identifying and combating pathogens such as bacteria, viruses, and other foreign invaders. These cells, also known as leukocytes, are diverse and include various types, such as lymphocytes (T cells and B cells), neutrophils, monocytes, and eosinophils. Each type has specific functions in recognizing antigens, producing antibodies, and coordinating the overall response to infections.

In contrast, red blood cells primarily transport oxygen from the lungs to the tissues and carbon dioxide from the tissues back to the lungs, rather than participating in immune functions. Platelets are involved in blood clotting and wound healing, and while plasma carries antibodies and other immune factors, it is not directly involved in the immune response in the same way that white blood cells are. Thus, the involvement of white blood cells in the immune response is essential for protecting the body against disease.