mmune system is body defence against infections.The imm-

une(in.myoon) system attack germs and help keep us healthy

parts of the immune system

many cells and organs work together to protect the body.

White blood cells also called leukocytes(loo-kuh-sites) play

an important role in the immune system.Some types of blood

cells called phygocytes(fa-hguh-sytes) chew up invading org-

nisms.others called lymphocytes(lim-fuh-sytes) helps the

body remember the invades and destroy them,One of the

phygcytes is the neutrophil,which fights the bacterias when

someone might have bacterial infection,doctors can order a

blood test to see if it caused the body to have lots of neutro-

phils.Other types of phagocytes do their own jobs to make

sure that the body respond to invaders.

The two kinds of lymphocytes are B-lymphocytes and

T-lymphocytes.Lymphocytes starts out in the bone marrow

and either stay there and mature into B-cells or go to the thy-

mus gland to mature into T-cells.B-lymphocytes are like the

military intelligence system.They find their targets and sends

defences to lock on to them,T-cells are like soldiers,they des-

troy invaders that the inteligence system find.

How does immune system work?

when the body senses foreign substances called antigens,

the immune system works to recognise the atigens and get

rid of them.B-lymphocytes are triggered to make antibodies

also called 9immunoglobin).These proteins lock onto specific

antigens;After they are made,antibodies usually stay in our

bodies in case we have to fight the same germs again thats

why someone who gets sick with a disese like chicken poxusually will not get sick again.This is also how immunizations

(vaccines) prevent some diseases.An immunization(vaccine)

introduces the body to an antigen in a way that dose not make

someone sick and let the body make antibodies that will prot-

ect the person from future attack by the germ.

Although antibodies can recognise an antigen and lock on it

they can not destroy it without help,thats the job of the T-cells.

They destroy antigens triggerd by antibodies or cells that are

affected or somehow changed,some T-cells are actually called

(killer cells).T-cells also help signal other cells (like phygocyte)

to do their job.These speciallised cells and parts of the immu-

ne system offer the body protection against diseases.This

protection is called immunity.Humans have three types of

immunity;

(1)inmate immunity-everyone is born with innate(or natural)

immunity,a type of general protection.For example ,the skin

acts as a barrier to block germs from entering the body and th

immune systemrecognises when certain invaders are foreign

and could be dangerous.

(2)Adaptive immunity-adaptive(or active) immunity develops

through out our lives,we develop adaptive immunity immunity

when we are exposed to diseases or whwn we are immunized

against them with a vaccine or medicine.

(3)Passive immunity-passive immunity is borrowed from anot-

her source and it lasts for a short time.For example,antibodies

in a mothers breast milk give a baby temporary immunity to

diseases the mother has been exposed to.The immune syste-

m takes a while to develop and needs help from the vaccine,

medication or diet.by getting all your childs recomended vacc-

ine,medication and diet on time ,you can help your baby keep

as healthy as possible . Immune system disorder

because the immune system is so complex,there are many

potential ways in which it can go wrong;

-be born with a weak immune system(this is called primary

immune deficiency)

-get a disease that weakens your immune system,this is call-

ed acquared immune deficiency

-have an immune system that is too high,this is happens with

an allergic reaction.

-have an immune system that turns against you,this is

called auto immune disease

Types of immune disorders falls into three categories;

(1)immunodeficiencies-these rise when one or more parties

of the immune system do not function,your immune system

can be weakened by certain medicine,chemotherapy,tran-

splant infections like flue virus,menonucleousis,measles,

HIV/AIDS and it can also be weakened by smoking,alcohol

poor nutritional and bubble boy disease.

(2)Autoimmunity-in this condition,the immune system mista-

kenly targets health cells rather than foreign pathogens or

faulty cells,common autoimmunity diseases are;

*diabetes-immune system attacks cells in the pancrease that

make insulin and insulin removes sugar from blood to use

as energy.

*Rhumatoid arthritis-causes swelling and deformities of joints

*Lupus-this disease attacks body tissues including lungs,kid-

neys and skin

*celiac disease,graves disease

*Hypersensitive-your body react to substance in the environ-

ment that are normally harmless.Allergic reactions to dust,

mold,pollen and food ,examples of diseases are;asthma,

eczema,allergic rhinitis.