What are Macrophages?

About Macrophages:

• Macrophages are a type of white blood cell that plays an important role in the human immune system.
• They are involved in the detection, phagocytosis, and destruction of bacteria and other harmful organisms.
• The term macrophage is formed by the combination of the Greek terms "makro" meaning big, and "phagein" meaning eat.
• They are essential for the maintenance and defence of host tissues, doing so by sensing and engulfing particulate matter and, when necessary, initiating a pro-inflammatory response. 
• They can modify themselves to form different structures in order to fight various different microbes and invaders. In this way, macrophages provide the first line of defense in protecting the host from infection.
• They are also involved in the development of non-specific or innate immunity.
• Macrophages produce a variety of cytokines, which are signaling molecules that communicate with other cells of the immune system. Cytokines play a role in inflammation, tissue repair, and the adaptive immune response.
• They migrate to and circulate within almost every tissue, patrolling for pathogens or eliminating dead cells.
• Macrophages may have different names according to where they function in the body. For example, macrophages present in the brain are termed microglia and in the liver sinusoids, they are called Kupffer cells.

What is Cellular Senescence?

• It refers to a state of stable cell cycle arrest in which proliferating cells become resistant to growth-promoting stimuli, typically in response to DNA damage. 
• During this phase, the cell undergoes numerous phenotypic and metabolic changes.
• Senescent cells accumulate during ageing and have been implicated in promoting a variety of age-related diseases.
• Cellular senescence can compromise tissue repair and regeneration, thereby contributing towards ageing.
• Removal of senescent cells can attenuate age-related tissue dysfunction and extend the health span.
• Senescence can also act as a potent anti-tumour mechanism by preventing the proliferation of potentially cancerous cells.

Q1) What is a Cell cycle?

A cell cycle is a series of events that takes place in a cell as it grows and divides. A cell spends most of its time in what is called interphase, and during this time it grows, replicates its chromosomes, and prepares for cell division. The cell then leaves interphase, undergoes mitosis, and completes its division.

Source: Senescent immune cells promote lung tumor growth: Study