What type of cells perform the immune function in the hematological system?

Leukocytes, or white blood cells, are the primary cells responsible for the immune function within the hematological system. Their role is essential in defending the body against infections and foreign invaders, such as bacteria, viruses, and parasites. Leukocytes can be further categorized into several types, including neutrophils, lymphocytes, monocytes, eosinophils, and basophils, each with specific functions in the immune response.

Neutrophils, for instance, are often the first responders to sites of infection and are critical for phagocytosing pathogens. Lymphocytes, which include T cells and B cells, are vital for adaptive immunity, helping to recognize and remember specific pathogens for faster responses during future exposures.

In contrast, platelets are primarily involved in hemostasis, assisting in blood clotting, and do not have a direct role in immune defense. Erythrocytes, or red blood cells, primarily function to transport oxygen to tissues and carry carbon dioxide away, lacking any immune function. Megakaryocytes are the large bone marrow cells that produce platelets and do not partake in immune activities either. Thus, leukocytes are the correct answer as they play the fundamental role in the immune response within the