Childhood Immune System Flashcards
The immune system
Innate or non-specific
Acquired, adaptive or specific
- cellular
- humoral
Innate immunity
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
Innate immunity
Physical barriers
Phagocytes (macrophages)
Immunological surveillance by No cells
Fever (systemic)
Inflammatory response (local)
Cytokines eg interferon
Complement the action of antibodies
Physical barriers
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
Phagocytes - they eat anything
Macrophages : fixes or mobile
Fixed
Neutrophils
Mobile
Monocytes
Eosinophils
Natural killer cells
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
Fever (systemic)
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
Inflammation
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
Inflammation
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
Inflammation
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
Acquired immunity
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
Acquired immunity
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
Lymphatic ducts
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
Cell mediated immunity
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
Cell mediated immunity
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
Humoral immunity
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
Immunity in early years
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
Antenatal passive immunisation
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
The immunological importance of breast milk
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
Immunity in early years
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
Development biology of the
immune system 0 Neutrophils Natural killer cells Macrophages 1 Cytotoxic T cells Plasma cells 2 antibody production
Polysaccharide antigen
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
Summary
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
