The im­mune sys­tem is your body’s re­ac­tion force against at­tacks from bad guys, from in­side and out. But how does it work ex­actly?

Your Baby & Toddler - - The Dossier -

WHAT MAKES US ILL? Vi­ral and bac­te­rial in­fec­tions are the big­gest cul­prits by far. Th­ese two vil­lains cause ill­nesses like cold, flu, mumps, chicken pox, gas­troen­teri­tis and ear in­fec­tions.

Our im­mune sys­tem’s main job is to pro­tect us against th­ese and other in­fec­tions. And it does so in three ways:

It cre­ates a bar­rier that pre­vents bac­te­ria and viruses from en­ter­ing the body.

If the bugs do find a way in, the im­mune sys­tem kicks in im­me­di­ately first to recog­nise the virus or bac­te­ria (and to later re­mem­ber it) and sec­ondly to shut it out.

If the germ does be­come com­fort­able in the hu­man body and mul­ti­plies, the im­mune sys­tem starts to elim­i­nate it.


Your im­mune sys­tem con­sists of var­i­ous com­po­nents spread through­out your body. Ev­ery com­po­nent has its own spe­cific func­tion.

One of the most ob­vi­ous is your skin, which is the main bound­ary be­tween germs and your body. Just like cling wrap pro­tects a sand­wich against germs, your skin stops cer­tain or­gan­isms from en­ter­ing your body.

Our nose, mouth and eyes are other ports through which germs can gain easy ac­cess to our bod­ies. In such cases, tears and mu­cus are the sol­diers stand­ing by

to kick out th­ese bugs. But some nasty germs do end up find­ing a way into our body. Rest as­sured, in­side your body they’ll have to pass by an­other bat­tal­ion of the im­mu­nity army. Th­ese sol­diers are all born, taken care of or pre­pared for bat­tle against harm­ful viruses and bac­te­ria in one of the fol­low­ing bases:

THYMUS GLAND The thymus gland is lo­cated in­side your chest – roughly be­tween your ster­num and your heart – and is re­spon­si­ble for the pro­duc­tion of T-cells.

Among other things th­ese cells se­crete small pro­teins that launch at­tacks on in­fected, foreign and can­cer­ous cells.

They lit­er­ally per­fo­rate th­ese cells so that other com­po­nents of the im­mune sys­tem have an eas­ier time get­ting rid of them. The thymus gland is es­pe­cially im­por­tant for new­borns, be­cause with­out it a baby’s im­mune sys­tem will col­lapse, and the baby will die.

BONE MAR­ROW Bone mar­row pro­duces new red and white blood cells, with the lat­ter prob­a­bly play­ing the most im­por­tant role in the im­mune sys­tem.

White blood cells join forces to de­stroy bac­te­ria and viruses that in­vade your body, and are also re­spon­si­ble for mak­ing an­ti­bod­ies. An­ti­bod­ies mark “at­tack­ers” in your body so that the fighter cells of the im­mune sys­tem can dec­i­mate them.

SPLEEN This or­gan fil­ters our blood and is con­stantly on the look­out for foreign cells in our blood or red blood cells that need re­place­ment. Peo­ple who have had their spleens re­moved can get by, but they fall ill much more often.

LYM­PHATIC SYS­TEM Doc­tors often tell par­ents to be vig­i­lant for swollen lymph nodes in their chil­dren’s necks. Lymph nodes swell when our body is fight­ing cer­tain bac­te­rial in­fec­tions – lit­er­ally be­cause of the ex­tra cells in the nodes that do bat­tle with bac­te­ria.

COM­PLE­MENT SYS­TEM The liver pro­duces pro­tein mol­e­cules (or com­ple­ments). Th­ese mol­e­cules bind in dif­fer­ent or­ders to ful­fil var­i­ous func­tions such as help­ing white blood cells con­sume foreign cells.

BORN THIS WAY? All the cells you need for im­mu­nity against spe­cific ill­nesses are present when you are born, but you have to be ex­posed to the spe­cific germ first to build im­mu­nity against it. This process con­tin­ues through­out your life.

Doc­tors dis­tin­guish be­tween re­sis­tance with which you’re born (nat­u­ral im­mu­nity) and re­sis­tance that de­vel­ops over time (ac­quired im­mu­nity). The lat­ter is what you get af­ter be­ing ex­posed to ill­nesses.

Some of the sol­diers in your im­mune sys­tem have the abil­ity to recog­nise and re­mem­ber foreign cells af­ter their first ex­po­sure, and then when a sec­ond meet­ing oc­curs, to launch an at­tack against them, ex­plains Dr Bar­bra-ann Saun­ders from the Free State Univer­sity’s pae­di­atric de­part­ment.

Al­though a healthy baby is born with all the nec­es­sary cells for a nor­mal im­mune sys­tem, new­borns all have a phys­i­o­log­i­cal de­fi­ciency.

“And the smaller or more pre­ma­ture the baby, the more pro­nounced the im­mune de­fi­ciency,” Bar­bra-ann says.

Mom trans­fers her an­ti­bod­ies to her un­born baby, but that only hap­pens quite late in the preg­nancy. This trans­fer pro­tects the baby for ap­prox­i­mately the first six months of his life. If a baby is born too early, this trans­fer has some­times not yet taken place.

Af­ter birth a baby is ex­posed to var­i­ous anti­gens (sub­stances that trig­ger a back­lash in the body; germs in this case). An­ti­bod­ies are pro­duced as a re­sult.

“Ini­tially, the an­ti­bod­ies are not of a good qual­ity, but by about eight weeks, ba­bies can start pro­duc­ing good-qual­ity an­ti­bod­ies,” Bar­bra-ann ex­plains.

By six months there will be enough an­ti­bod­ies, but im­mune-sys­tem ma­tu­rity is still a way off. The var­i­ous an­ti­bod­ies be­come ma­ture at dif­fer­ent ages: some at four or five years, oth­ers only at seven or eight and quite a few only dur­ing the teenage years.

It’s hard to be­lieve but ill­ness is ac­tu­ally a good thing for your lit­tle one, be­cause ev­ery time he falls ill, the lym­pho­cytes of the im­mune sys­tem are ex­posed to an­other anti­gen.

In this way an­ti­bod­ies de­velop that pro­tect your child against that spe­cific or­gan­ism, when the germ strikes again.

This is ex­actly why im­mu­ni­sa­tion is so ef­fec­tive – it ex­poses the body to a spe­cific anti­gen (germ) so that an­ti­bod­ies de­velop and your child is pro­tected against that dan­ger­ous ill­ness.

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