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The three major groups of lymphocytes include natural killer cells, B cells, and T cells. Natural killer (NK) cells are capable of recognizing cells that do not express “self” proteins on their plasma membrane or that contain foreign or abnormal markers. These “nonself” cells include cancer cells, cells infected with a virus, and other cells with atypical surface proteins. Thus, they provide generalized, nonspecific immunity. The larger lymphocytes are typically NK cells.

B cells and T cells, also called B lymphocytes    and T lymphocytes    , play prominent roles in defending the body against specific pathogens (disease-causing microorganisms) and are involved in specific immunity. One form of B cells (plasma cells) produces the antibodies or immunoglobulins that bind to specific foreign or abnormal components of plasma membranes. This is also referred to as humoral (body fluid) immunity. T cells provide cellular-level immunity by physically attacking foreign or diseased cells. A memory cell    is a variety of both B and T cells that forms after exposure to a pathogen and mounts rapid responses upon subsequent exposures. Unlike other leukocytes, memory cells live for many years. B cells undergo a maturation process in the b one marrow, whereas T cells undergo maturation in the t hymus. This site of the maturation process gives rise to the name B and T cells. The functions of lymphocytes are complex and will be covered in detail in the chapter covering the lymphatic system and immunity. Smaller lymphocytes are either B or T cells, although they cannot be differentiated in a normal blood smear.

Abnormally high lymphocyte counts are characteristic of viral infections as well as some types of cancer. Abnormally low lymphocyte counts are characteristic of prolonged (chronic) illness or immunosuppression, including that caused by HIV infection and drug therapies that often involve steroids.

Monocytes originate from myeloid stem cells. They normally represent 2–8 percent of the total leukocyte count. They are typically easily recognized by their large size of 12–20 µ m and indented or horseshoe-shaped nuclei. Macrophages are monocytes that have left the circulation and phagocytize debris, foreign pathogens, worn-out erythrocytes, and many other dead, worn out, or damaged cells. Macrophages also release antimicrobial defensins and chemotactic chemicals that attract other leukocytes to the site of an infection. Some macrophages occupy fixed locations, whereas others wander through the tissue fluid.

Abnormally high counts of monocytes are associated with viral or fungal infections, tuberculosis, and some forms of leukemia and other chronic diseases. Abnormally low counts are typically caused by suppression of the bone marrow.

Lifecycle of leukocytes

Most leukocytes have a relatively short lifespan, typically measured in hours or days. Production of all leukocytes begins in the bone marrow under the influence of CSFs and interleukins. Secondary production and maturation of lymphocytes occurs in specific regions of lymphatic tissue known as germinal centers. Lymphocytes are fully capable of mitosis and may produce clones of cells with identical properties. This capacity enables an individual to maintain immunity throughout life to many threats that have been encountered in the past.

Questions & Answers

why the heart is protected with that sac
Joshua Reply
To prevent collision with the lungs, lubricates the heart, protects the heart from infection in the event a peripheral organ is effected, and stabilizes the heart within the mediastinum.
This app should be updated too much as there is very little information for some topics.I hope you will consider my information....
aman Reply
adenohypophysis is made up of what type of cells and what is the name of those cells?
Mannu Reply
armstrong Reply
motor root of the trigeminal nerve
what is the nervous system about
what passes through foramen ovale?
Farah Reply
what are the organelles of a cell
Amina Reply
muscular system
nucleus ribosome Golgi body call membrane cytoplasm
these are the cellular components that functions to provide energy,remove waste and cell division
Organelles of the cell are: Mitochondria,Ribosome,golgi apparatus, nucleus, secretory granules, nuclear e t c
what are local hormones
Local hormones are hormones that effect the cell that released them or cells near the releasing cell and they do not circulate within the blood stream.
the trachea bifurcated into how many branches on the right lung
three lobes
Explain the normal flow of blood.
how can we maintain the internal living things
Choolwe Reply
how many seconds does a human will stop if you sneeze
Kharl Reply
1 sec not specific
physiology of vision
Sudipta Reply
Can pure water become gel like?
ovie Reply
what is Homeostasis
Laura Reply
It is the ability of an organism to co ordinate it's internal environment so as to achieve balance in all areas
what is anatomy
Sandra Reply
what is physiology
The study of how the body works
the branch of biology dealing with the functions and activities of leaving organisms and their parts including all physical and chemical processes
the study of human body . phicically and chemically it's called anotomy physiology
the branch of biology dealing with the functions and activities of living organisms
which vein do we inject to give infusions
it is the scientific study of the body structure
What Choolwe Muselitata said is the definition of anatomy
Physiology can also be described as the way in which a living organism or bodily part functions
Anotomy is the science which we humen body of structure and function know as the anotomy
study of the body funtion and structure
functional study of the body
it is the study about the functions of body organs
what are the vital sign procedure
jeniffer Reply
You start the TPR then BP after explaining the procedure to the patient and your requirements ready.
which type of vein to you inject to give infusions?
how long do u take radial pulse
Flavian Reply
1 minute
You can take it for 15 seconds , the number you got you multiply wth 2
but in the aspect of the multiplying that isn't right
radial pulse kya hai?
for more accurate values you must do the 1 minute
1 minute.
60 seconds
1 minute
yes @sabina
What is homeostasis
Winter Reply
Homeostasis is the state of relative stability of the body's environment
what are fluids
fluid is a substance that has no fixed shape and yield easily to external pressure
Difference between hemostasis and homeostasis
Hemostasis is blocking or stopping blood flow from a damaged blood vessel by coagulation of that vessel or obstructing it.
Homeostasis is a balanced state. An equilibrium. The body does this by regulating itself by using hormones and neurotransmitters to keep chemicals balanced within the body.
Examples of site of homeostasis
For example, to much calcium in the blood would stimulate the release of calcitonin from the thyroid gland. Calcitonin will decrease calcium levels by depositing it into the skeleton. This is known as bone deposition, a homeostatic mechanism. Parathyroid hormone is the opposite to calcitonin.
There are a lot of homeostatic mechanisms in the body. Insulin and glucagon is another one. These two regulate glucose (sugar) levels in the blood. High glucose levels would cause insulin from the pancreas beta cells. Insulin lowers blood sugar. Glucagon increases blood sugar

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