natural killer cells definition

Natural killer (NK) cells are cytotoxic lymphocytes that play a vital role in innate immunity by identifying and destroying cells that appear abnormal or are infected, primarily through changes in major histocompatibility complex (MHC) I expression. They induce apoptosis in these cells without the need for prior antigen sensitization, making them a swift response against infections and cancers.

Natural killer (NK) cells are a critical component of the innate immune response, functioning as cytotoxic lymphocytes. These NK cells patrol the body, seeking out cells that exhibit 'non-self' proteins on their membranes or that have foreign or abnormal markers indicative of infection or cellular transformation, such as that which occurs in cancer. Unlike T cells of the adaptive immune response, NK cells do not require prior sensitization to specific antigens and thus provide a rapid response to invasions or cellular abnormalities.

One way NK cells are able to discern unhealthy cells from healthy ones involves the detection of changes in the expression of major histocompatibility complex (MHC) I molecules on the surface of nucleated cells. Healthy cells present normal 'self' peptides via MHC I to the immune system, signaling their healthy state. Conversely, cells that are infected or becoming cancerous often have altered MHC I expression, which is recognized by NK cells, triggering a targeted response.

Once an NK cell identifies a potential target, they can induce apoptosis, or programmed cell death, within the aberrant cell. Through the release of cytotoxic granules, NK cells deliver potent molecules like perforin and granzymes, which penetrate the target cell's membrane and initiate the apoptosis cascade, leading to cell death and the removal of the threat they posed.

The release of large quantities of merozoites into circulation at one time is due to a form of reproduction by plasmodium known as __________.

Over the past century, the global sea level has risen by 4 to 8 inches. However, over the last 20 years this increase has been occurring at approximately twice the average speed of the preceding 80 years.
__________ is NOT a cause for this increased global sea level.
A) Thermal expansion
B) Melting of glaciers and polar ice caps
C) Ice loss from Greenland and West Antarctica
D) An increase in the water present in the water cycle

Avery is examining cells under the microscope. she is using the 40x objective to view the slide with a 10x eyepiece. what is the total magnification she is using to view the cells?

Type of heredity that produces a blend of the dominant and recessive is calle

In a population of birds, individuals with small beaks are well-adapted to feeding on small seeds. other individuals with large beaks are also well-adapted to feeding on large seeds. however, individuals with medium-sized beaks are at a relative disadvantage since they have difficulty feeding on small and large seeds (and there are no medium-sized seeds available). over time, _____ may lead to the formation of two distinct bird species from this original bird population.

A small number of birds arrive on an island from a neighboring larger island. This small population begins to adapt to the new food plants available on the island, and their beaks begin to change. About twice a year, one or two more birds from the neighboring island arrive. These new arrivals _____.

What is true about the absorption and transportation of fat in the blood?

Cholera-causing bacteria have a single flagellum that allows these bacteria to ?

A microbe that enters the vagina would likely cause cystitis if left untreated. a microbe that enters the vagina would likely cause cystitis if left untreated.
a. True
b. False

What treats the body using principles similar to acupuncture and acupressure?

hormones that are secreted by the posterior pituitary gland are made in the

Definition: these are physical features shared by organisms with common ancestry; they may have the same structure, but different functions developmentally mature organisms.

In an inducible operon, the inducer is often the __________ in the pathway being regulated; the inducer binds to the __________, thus rendering it __________.

Which two hormones are consistently related to high levels of aggression?

Consider the mammalian heart. why is the muscular wall of the left ventricle thicker than that of the right ventricle? the left ventricle has more nerve endings for contraction, and more muscle mass must be there to accommodate the extra neurons. this difference stems from the fact that frogs have a thicker left ventricular muscle mass. the ventricle wall must be thicker to inhibit diffusion between the right and left ventricle. the left ventricle must contract with more force in order to send blood to the body's extremities.

Which organic molecules are nucleic acids?
A. Enzymes and protiens
B. Lipids and carbohydrates
C. Dna and rna
D. Glycogen and atp

The Cahuilla tribe was a Native American community that lived in the arid area near present day San Diego. The Cahuilla's diet relied heavily upon mesquite beans. In order to preserve the plants only a portion of the beans that were available to harvest were harvested. Why were some of the harvestable beans left on the plant?
A) for wildlife to eat
B) for later harvest
C) to grow into new plants
D) lack of room in the harvest basket

the formula for the table salt is NaCI. According to the law of definite proportions, this means that the formula for the table salt

Personality assessments conducted by behaviorists sometimes make use of _______. (1 point) question 56 options: 1) projective tests 2) introjective tests 3) reports by friends 4) responses to hypothetical situations 5) rating scales and frequency counts

When the body is attacked by a foreign substance, the what defenses are the first to react

Which of the following is a primary function of the skeletal system?
A. Maintaining body temp.
B. Supporting body weight
C. Filtering nitrogenous wast from the body
D. Coordinating nervous responses from the body

Which cells in the seminiferous tubules regularly undergo mitosis?

There are 7 oak trees and 32 pine trees in the park. how many trees are in the park

Charlie contracted Lyme disease when he was bitten by a tick, which is a small spider-like animal. The tick carries harmful bacteria that was released into Charlie’s blood. Which list best classifies the causes of Lyme disease?

Which product is made from renewable resource?
A. Blueberry pie
B. Gold ring
C. Kaolin porcelain
D. Aluminum can

State the reason why some drugs are considered drugs of abuse.

Which direction do a comet's dust and plasma tails point?

Transformation did not occur when dna was destroyed true or false

what bacterial species can be eliminated as possibilities for the bacteria responsible for Anna's infection?

The cardiovascular system of a mouse works like that of a human. a mouse is moved from sea level (low altitude) to the top of a mountain (high altitude). how could this mouse's cardiovascular system maintain a similar rate of oxygen delivery to its tissues now that the mouse is at the top of the mountain?