immune system components

8/6/2019 immune system components

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ANTIBODIES

A ntibodies (also referred to as immunoglobulins and gammaglobulins) are are Y-shaped proteins that respond to specific bacteria, viruses or toxins, called

antigens. They are produced by white blood cells. A ntibodies can bind to toxins, disabling their chemical actions or signal that

an invader needs to be removed.

These antibodies are divided into five classes. Their names are generally

BONE MARROW

Bone marrow produces new red and white blood cells.

Red blood cells are fully formed in the marrow and then enter thebloodstream.

Most white blood cells mature elsewhere, however, in factories locatedinside the long bones of our bodies.

The marrow produces all blood cells from stem cells.

They are called "stem cells" because they are precursors to different celltypes.

They can branch off and change into specific types of white blood cells, asneeded.


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THE COMPLEMENT SYSTEM

The first part of the immune system that meets invaders such as bacteriais a group of proteins called the complement sys tem .

These proteins flow freely in the blood and can quickly reach the site of an invasion where they can react directly with a ntigen s - molecules that the body recognizes as foreign substances. When activated, thecomplement proteins can:

- trigger inflammation

- attract eater cells such as macrophages to the area

- coat intruders so that eater cells are more likely to devour them

- kill intruders


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Ph a goc yte s

This is a group of immune cells specialized in finding and "eating"bacteria, viruses, and dead or injured body cells.

There are three main types, the granulocyte, the macrophage, and thedendritic cell.

Gr a nuloc yte s

The g r a nuloc yte s often take the first standduring an infection.

They attack any invaders in large numbers, and

"eat" until they die. The pus in an infected wound consists chiefly of

dead granulocytes. A small part of the granulocyte community is

specialized in attacking larger parasites such asworms.

Ma crop h a ge s

The m a crop h a ge s ("big eaters") are slower to respondto invaders than the granulocytes, but they are larger,live longer, and have far greater capacities.

Macrophages also play a key part in alerting the rest of the immune system of invaders.

Macrophages start out as white blood cells calledmonocytes.

Monoc yte s that leave the blood stream turn intomacrophages.


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Dend r itic cell s

The dend r itic cell s are "eater" cells and devourintruders, like the granulocytes and the macrophages.

A nd like the macrophages, the dendritic cells help withthe activation of the rest of the immune system.

They are also capable of filtering body fluids to clearthem of foreign organisms and particles.

LYMPHOCYTES - T CELLS AND B CELLS

Th e lymp h a tic sys tem

Th e recepto rs m a tc h onl y one

s pecific a ntigen.

WHITE BLOOD CELLS

Wh ite b lood cell s called lymphocytes originate in the bone marrow but migrate to parts of the lymphatic system such as the lymph nodes, spleen,and thymus.


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There are two main types of lymphatic cells, T cell s a nd B cell s .

The lymphatic system also involves a transportation system - lymphvessels - for transportation and storage of lymphocyte cells within thebody.

The lymphatic system feeds cells into the body and filters out dead cellsand invading organisms such as bacteria.

y O n the surface of each lymphatic cell are receptors that enable them torecognize foreign substances. These receptors are very specialized - each canmatch only one specific antigen.

y To understand the receptors, think of a hand that can only grab one specificitem. I magine that your hands could only pick up apples. You would be a true

apple-picking champion - but you wouldn't be able to pick up anything else.

y I n your body, each single receptor equals a hand in search of its "apple." Thelymphocyte cells travel through your body until they find an antigen of the right size and shape to match their specific receptors. I t might seem limiting that thereceptors of each lymphocyte cell can only match one specific type of antigen,but the body makes up for this by producing so many different lymphocyte cellsthat the immune system can recognize nearly all invaders.

T CELLS

T cell s come in two different types, h elpe r cell s a nd kille r cell s .

They are named T cells after the thymus, an organ situated under thebreastbone.

T cells are produced in the bone marrow and later move to the thymus

where they mature.


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Helpe r T cell s

are the major driving force and the main regulators of the immune defense.

Their primary task is to activate B cells and killer T cells.However, the helper T cells themselves must beactivated. This happens when a macrophage or dendriticcell, which has eaten an invader, travels to the nearest lymph node to present information about the capturedpathogen.

The phagocyte displays an antigen fragment from the

invader on its own surface, a process calleda

ntigen p re s ent a tion .

When the receptor of a helper T cell recognizes theantigen, the T cell is activated. O nce activated, helper Tcells start to divide and to produce proteins that activateB and T cells as well as other immune cells.


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K ille r T cell

The kille r T cell is specialized in attacking cells of the body infected byviruses and sometimes also by bacteria.

I t can also attack cancer cells.

The killer T cell has receptors that are used to search each cell that it meets.

I f a cell is infected, it is swiftly killed.

I nfected cells are recognized because tiny traces of the intruder, antigen, canbe found on their surface.


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B Cell s

The B lymp h oc yte cell searches for antigen matching its receptors.

I f it finds such antigen it connects to it, and inside the B cell a triggering

signal is set off.

The B cell now needs proteins produced by helper T cells to become fullyactivated.

When this happens, the B cell starts to divide to produce clones of itself.During this process, two new cell types are created, pl a s m a cell s a nd Bmemo ry cell s .

P la s m a cell

The pl a s m a cell is specialized in producing a specific protein, calledan a nti b od y , that will respond to the same antigen that matched the B cellreceptor.

A ntibodies are released from the plasma cell so that they can seek out intruders and help destroy them.

P lasma cells produce antibodies at an amazing rate and can release tens of thousands of antibodies per second.

y When the Y-shaped antibody finds a matching antigen, it attaches to it.

y The attached antibodies serve as an appetizing coating for eater cells such as themacrophage.

y A ntibodies also neutralize toxins and incapacitate viruses, preventing them frominfecting new cells.

y Each branch of the Y-shaped antibody can bind to a different antigen, so whileone branch binds to an antigen on one cell, the other branch could bind toanother cell - in this way pathogens are gathered into larger groups that areeasier for phagocyte cells to devour.

y Bacteria and other pathogens covered with antibodies are also more likely to beattacked by the proteins from the complement system.


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Memo ry C ell s

The Memo ry C ell s are the second cell type produced by the division of B cells.

These cells have a prolonged life span and can thereby "remember" specificintruders.

T cells can also produce memory cells with an even longer life span than B memory cells. The second time an intruder tries to invade the body, B and Tmemory cells help the immune system to activate much faster.

The invaders are wiped out before the infected human feels any symptoms.The body has achieved immunity against the invader.


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TONSILS

Tonsils are made of soft glandular tissue and are part of the immunesystem. You have two tonsils, one on either side at the back of the mouth.

Tonsils vary in size from person to person.

A main function of tonsils is to trap bacteria and viruses (germs) whichyou may breathe in. A ntibodies and immune cells in the tonsils help to killgerms and help to prevent throat and lung infections.

You can normally see your tonsils by opening your mouth wide andlooking in a mirror. They are the two fleshy lumps that you can see at thesides and back of the mouth.

ADENOIDS

A denoids help to defend the body from infection.

They trap bacteria and viruses which you breathe in through your nose.

They contain cells and antibodies of the immune system to help prevent throat and lung infections.

HORMONES

There are several hormones generated by the immune system. Thesehormones are generally known as lymphokines. Some hormones in the


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body suppress the immune system. These are the steroids andcorticosteroids (components of adrenaline).

Ly mp h node s are basically filters that trap germs and other foreignbodies. The nodes have armies of lymphocytes to deal with the germs.Lymphocytes are a type of white blood cell, which neutralizes or destroysgerms. The lymph nodes can become swollen when fighting an infection.

Lymphoid organs include the bone marrow and the thymus, as well aslymph nodes, spleen, tonsils and adenoids, the appendix, and clumps of lymphoid tissue in the small intestine known as P eyer's patches.

There are about 2 to 4 pints of lymph fluid in the average body.

SPLEEN

The spleen filters the blood looking for foreign cells.

The spleen is also looking for old red blood cells that need replacement.

I t is an organ about the size of a fist in the upper left of the abdomen.

The spleen contains two main types of tissue: r ed ti ss ue that disposesof worn-out blood cells, and w h ite ti ss ue that contains lymphoid tissue.

Different part of the spleen specialize in different kinds of immune cells.When microorganisms get carried by the blood into the red tissue, theybecome trapped by the immune cells known as macrophages.


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THYMUS

The thymus is located in your chest, between your breast bone and yourheart.

I t is responsible for producing T-cells and is important for T cellmaturation. The thymus actually chooses which T-cells are best suited forthe immune system. The remaining ones are eliminated by the body,assuring a healthy, effective immunity.

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