Question

Select cells that can kill bacteria using both phagocytic and nonphagocytic means

Answer 1

There are many cells in our immune system that keeps on circulating in our lymphatic system or circulatory system and helps in eliminating the foreign pathogen out from the body system that can cause threat to the system.

Cells that kills the bacteria by phagocytosis are- Macrophages, Dendritic cells, Neutrophills, B-lymphocytes.

When the body encounters bacteria, these phagocytic cells starts accumulating at that particular site. These cells engulf the bacteria. Bacteria is engulfed in the form of a vesicle known as phagosome. On reaching inside the cell, this phagosome gets fuse with the lysosome. On fusion, a structure called phagolysosome is fomed. Due to presence of hydrolytic enzymes and increased acidic condition, the bacterail cell is killed and the debris are exocytosed.

Cells which kills the bactera by non-phagocytic means are- Mast cell and Basophils. Both these cells secrete histamine.

Mast cells mediates the innate immune system of an organism. They undergo degranulation and secretes histamine which is a vasomediator substance that dilates the blood vessels and increase the permeability and increased blood flow in the localized area. These cells also stimulates mucous epithelium to secrete mucous that will cause the immobilization of the bacteria that has entered the body. Histamine also act as a chemotactic agent that attracts NK cells, neutrophils and eosinophils which causes bacterial cell killing. They also helps adaptive immune response by causing enhanced migration of dendritic cells and T-lymphocyes at the site of infection.

Basophils are also responsible for secretion of histamine. They also have the similar killing mechamism as that of mast cells. But basophils only helps in activation of innate immune response and not adaptive immune response.