Question

Match each cellular defense with the infection it would most likely target. natural killer cell A. virus-infected cell neutrophil B. tapeworm in the intestines eosinophil C. bacteria in a skin lesion

Short answer

Natural killer cell - A. virus-infected cell, Neutrophil - C. bacteria in a skin lesion, Eosinophil - B. tapeworm in the intestines.

Step-by-step solution

Identify the function of Natural Killer Cells

Natural killer cells are a type of lymphocyte and a component of the innate immune system which do not require antigen activation. They recognize infected or stressed cells, often by viruses, and induce apoptosis (cell death).

Identify the function of Neutrophils

Neutrophils are a type of white blood cell and part of the body's first line of defense. They are especially equipped to ingest and destroy pathogens like bacteria through a process called phagocytosis.

Identify the function of Eosinophils

Eosinophils are white blood cells that are responsible for combating multicellular parasites such as worms. They also play a role in allergic responses.

Match the cellular defense with its target

Using the information identified in previous steps, match natural killer cells to virus-infected cells (A), neutrophils to bacteria in a skin lesion (C), and eosinophils to a tapeworm in the intestines (B).

Key concepts

Innate Immunity

Innate immunity represents the body's first line of defense against pathogens. It includes physical barriers like skin, mucous membranes, and also a variety of immune cells that act immediately or within hours of an antigen's appearance in the body. Unlike adaptive immunity, innate immunity does not require previous exposure to a pathogen or its toxins to be activated.

Key components of innate immunity involve a range of cells and mechanisms that work in a nonspecific manner, meaning they target a broad array of invaders without the need for precise identification. This can include various white blood cells, such as natural killer cells, neutrophils, and eosinophils, which have different roles in defending the body from infection.

Natural Killer Cells

Natural killer (NK) cells play a crucial role in the body's defense against tumors and virally infected cells. These lymphocytes act without the need for antigen presentation and do not rely on the slower adaptive immune response. NK cells are equipped with receptors that help them detect cells with reduced levels of MHC (major histocompatibility complex) molecules, which is often indicative of infection or cancer. Once they identify a target, NK cells release cytotoxic granules that trigger apoptosis, thus eliminating the compromised cell.

By inducing apoptosis rather than necrosis, fewer inflammatory signals are produced, which helps to prevent collateral damage to the surrounding tissue.

Neutrophils

Neutrophils are the most abundant white blood cells in the bloodstream. They act as one of the body's initial cellular responses to an infection, particularly against bacteria and fungi. When an infection arises, they are rapidly deployed to the site, where they encapsulate and ingest pathogens by a method known as phagocytosis. After engulfing the microbe, neutrophils use toxic chemicals and enzymes to kill and digest it.

These cells also release signaling molecules that can attract other immune cells to the site of infection, amplifying the immune response. A buildup of spent neutrophils in affected tissues can lead to the formation of pus.

Eosinophils

Eosinophils, another type of white blood cell, are primarily associated with combating multicellular parasitic infections, like those caused by worms, and also with allergic diseases. They have granules that contain toxic compounds which can be released to kill the parasites. Eosinophils work by attaching to the parasite and releasing these substances to weaken or kill it.

Aside from their role in immunity against parasites, eosinophils may also regulate mechanisms of inflammation and influence the inflammatory process. Elevated eosinophil counts are often seen in various allergic reactions, including asthma.

Phagocytosis

Phagocytosis is a crucial process utilized by certain immune cells, such as neutrophils and macrophages, to clear pathogens from the body. During phagocytosis, the immune cell surrounds and engulfs particles such as bacteria, dead cells, and small cell fragments. These are then trapped within a compartment known as a phagosome.

The phagosome merges with a lysosome, another cellular organelle that contains digestive enzymes and toxic substances, forming a phagolysosome. The contents of the lysosome digest the pathogen, effectively destroying it. This mechanism is part of the innate immune response, providing a rapid action against infection.

Apoptosis

Apoptosis, often referred to as programmed cell death, is a vital process that allows the body to remove unwanted or damaged cells without causing an inflammatory response. Apoptosis can be triggered by signals from within the cell or external signals, such as those from NK cells or T lymphocytes. The cellular contents are contained within apoptotic bodies that are subsequently engulfed by phagocytes, preventing leakage and potential damage to neighboring cells.

This biochemical cascade is critical not only for defending against diseases such as cancer and viral infections but also for normal growth and development, as it allows for tissue remodeling and the elimination of unnecessary cells during processes such as embryogenesis.