Childhood Immune System

Question 1

The immune system

Answer 1

Innate or non-specific

Acquired, adaptive or specific

• cellular
• humoral

Question 2

Innate immunity

Answer 2

Also know as non specific immunity

Provides a first line of body defence which can respond within minutes to foreign substances

Consist of surface membrane barriers, chemicals and immune cells

Question 3

Innate immunity

Answer 3

Physical barriers

Phagocytes (macrophages)

Immunological surveillance by No cells

Fever (systemic)

Inflammatory response (local)

Cytokines eg interferon

Complement the action of antibodies

Question 4

Physical barriers

Answer 4

Intact skin - provides a barrier to entry by pathogens

Acidic pH of the skin I gain it’s bacterial growth

Intact mucous membranes form a barrier to micro- organisms

Mucus traps micro-organisms

Cilia transports debris laden mucus away from lower respiratory tract

Question 5

Phagocytes - they eat anything

Answer 5

Macrophages : fixes or mobile

Fixed
Neutrophils

Mobile
Monocytes

Eosinophils

Question 6

Natural killer cells

Answer 6

Large granular lymphocytes

Attack foreign cells or body cells infected with viruses, and cancer cells that appear in normal tissue

Natural killers cells trawl around the body acting as surveillance proline

Question 7

Fever (systemic)

Answer 7

Moderate fever is a systemic response initiated by cytokines called pyrogens

The hypothalamus raise the body temperature in response to pyrogens

Raising body temperature

• inhibits microbial multiplication
• mobilises the immune system
• enhances tissue repair processes

Very high fever can be dangerous to the body causing enzymes to denature

In young children a rapidly rising body temperature can cause febrile convulsions

Question 8

Inflammation

Answer 8

Inflammation is a normal physiological response

Occurs following physical trauma, intense heat, chemical damage and infections

Classic signs

• swelling (tumor)
• redness (rubor)
• heat (calor)
• pain (dolor)

Blood flow increases 
Phagocytes activated
Capillary permeability increased 
Complement activated 
Clotting reaction walls off region
Regional temperature increase 
Specific defenders activated

Question 9

Inflammation

Answer 9

The inflammation response is beneficial because

Prevents the spread of toxic agents to adjacent tissue

Disposed of pathogens and dead tissue cells

Promotes tissue repair and attracts immune cells to the site of damage

Question 10

Inflammation

Answer 10

Bacteria and other pathogens enter wound

Platelets from blood release blood clotting proteins at wound site

Mast cells secrete factors that mediate vasodilation and vascular constriction. Delivery of blood, plasma, and cells to injured area increases

Neutrophils secrete factors that kill and degrade pathogens

Neutrophils and macrophages remove pathogens by phagocytosis

Macrophages secrete hormones called cytokines that attract Timmy was system cells to the site and activate cell involved in tissue repair

Inflammatory response continues until the foreign material is eliminated and the wound is repaired

Question 11

Acquired immunity

Answer 11

Refers to an antigen specific immune response

Is a more complex response than the innate immune response

Recognises the antigen and non self and then creates a large number of cells specifically designed to attack that antigen

Question 12

Acquired immunity

Answer 12

Cell mediated immunity - T lymphocytes respond to a specific antigen that then activated phagocytes, other lymphocytes, and the release of various cytokines

Humoral immunity - refers to antibody production by B lymphocytes in response to an antigen

Question 13

Lymphatic ducts

Answer 13

Tonsil

Thymus

Spleen

Peters patches

Lymph nodes contain specialised compartments where immune cells can congregate and encounter antigens

Lymph nodes act like water filters, removing antigens before the lymph drains back into the venous blood

The spleen removes abnormal blood cells by phagocytosis stores iron and initiates the immune result b and T cells in the circulating blood

Question 14

Cell mediated immunity

Answer 14

Cell mediated immunity involves an interaction between antigen presenting cells and t helper cells

APC phagocytes, process and present the antigens on its surface

APC enters the lymph system where is meets many T helper cells in the lymph nodes. If there is a match between the antigens and the t helper cells receptors, then that T helper cell is activated

An activated the T helper cell divides rapidly and secretes small proteins cells cytokines that regulate and amplify the immune response

A subset of the T cells go on to form memory cell which increase the efficiency of any future exposure to the same antigen

Question 15

Cell mediated immunity

Answer 15

Cell mediated immunity is most effective at attacking microbe infected cells

It also active in fighting

• fungi and protozoan infections
• intracelluar bacteria
• cancer cells

It also plays a major role in transplant rejection

Question 16

Humoral immunity

Answer 16

Humoral immunity is based on an interaction between an antigen and a the antigen-specific surface receipt of a B cell

When this interaction takes place, the B cell becomes activated

An activated B cell multiplies forming many plasma cells and it is these plasma cells that secrete large amounts of antigens specific antibodies

The antibodies are free to diffuse through the extracellular space throughout most of the body including the blood

These antibodies bind to the antibodies of the surface of the invading material

Material coated in antibody is targeted by the other elements of the immune system, which all leads to the destruction and removal of material

A subset of the B cells go on to form memory cells which increases the efficiency of any future exposure to the same antigens

Question 17

Immunity in early years

Answer 17

The adaptive immune system in babies and young children is immature and lack of memory cells

There is a greater reliance on non specific immunity and passive immunisation from across the placenta and breast milk

While most innate development takes place prior to starting school, full immunological capacity is not reached until late childhood/ early adolescence

Question 18

Antenatal passive immunisation

Answer 18

Maternal IgG is actively transported to the foetus via the placenta in the 3rd trimester

At term the neonate has a higher concentration of IgG than the mother

The IgG that the body has at both is a reflection of maternal immunological memory and is slowly defended and lost by 3 months of age

Question 19

The immunological importance of breast milk

Answer 19

Colostrum is particularly rich in antibodies

Breast milk contained cytokines, antibacterial agents and immune cells

IgA is present t in breast milk, it is highly reactive to environmental pathogens and protects the neonatal mucosa of the fur and respiratory tract

The immune cells in breast milk stimulate the inflames own production of IgA

Question 20

Immunity in early years

Answer 20

While some b and T cells numbers are found in high numbers in 1st years of life

Their function in the young child is poor

They are less responsive to stimulus and need stronger stimulation before responding

Numbers of t and b meme pry cells are low in young children due to the lack of exposure to infections ie the cells are naive

Question 21

Development biology of the

Answer 21

immune system 
 0
Neutrophils 
Natural killer cells 
Macrophages 
1 
Cytotoxic T cells 
Plasma cells 
2 antibody production

Question 22

Polysaccharide antigen

Answer 22

Infants and young children have impaired immunity to polysaccharide antigens

Children with chronic diseases such as sickle cell disease need prophylactic antibodies (penicillin) for the first five years to protect them

Question 23

Summary

Answer 23

Babies and young children are at increasing risk of infection due to immature immune system and lack of immunological memory

New born Bavaria get the benign of trans placental passive immunisation and the. Breast feeding

With exposure to infection over time they build up immune memory and with maturation of the elements of the immune system that achieve maturity of the immune system by early adolescence