What type of cell is characterized as an amoeboid cell that engulfs bacteria and dead cells?

The correct answer is macrophage. Macrophages are specialized immune cells that have the ability to change shape, which allows them to move easily through tissues and engulf pathogens such as bacteria, as well as dead cells through a process called phagocytosis. This characteristic amoeboid movement is crucial for their role in the immune response, as they patrol the body and respond to sites of infection or injury.

Macrophages play a significant role in both the innate and adaptive immune systems. They not only eliminate debris and pathogens but also help activate other immune cells by presenting antigens and releasing signaling molecules known as cytokines. This function is essential for maintaining tissue homeostasis and initiating the healing process after tissue damage.

In contrast, memory cells are a type of lymphocyte that persist in the body after an infection has resolved and help provide long-lasting immunity. Pathogens refer to the microorganisms that can cause disease, including bacteria, viruses, and fungi, but do not refer to a specific type of immune cell. T lymphocytes, another important part of the immune system, play roles in cell-mediated immunity and killing infected host cells rather than directly engulfing debris or pathogens like macrophages do.