Immunity And Infection Flashcards
4 areas involved in immunity
BTLS
BONE MARROW= Long bones, iliac crest and sternum
Red bone marrow is epiphyses of bones (produces WBC, RBC and platelets)
Yellow = fats in shaft of long bones
THYMUS GLAND- Develops T lymphocytes
Pericardial cavity and quite small
Larger as a child
LYMPH NODES- holds immunity cells. Near vascular system to exchange cells
SPLEEN AND TONSILS- tonsils holding areas for immune cells
Spleen stores and recycles RBCs, stores WBCs and platelets
Two types of Immunity
Cell mediated
Humoral immunity / antibody mediated immunity
What does cell mediated do?
Fight intracellular pathogens
Track cancer cells
Tissue transplants
Where are T and B cells produced ?
Formed in red bone marrow @ ends of long bones and foetal liver
T LYMPHOCYTES
Released from bone marrow as immature
Travel through blood to thymus gland
Thymus gland activates T cells by adding components to it
T cells leave thymus gland as mature
T cells stored in the lymphatic system
Two types of T cells :
CD 4 T cells (T helper)
CD8 T cells (T killer)
CD4+ and CD8+ combine to form killer T cells
T cells use phagocytosis to ingest and engulf pathogens, remove damaged tissues and eat up pre cancerous cells
What happens if someone has a transplant?
Killer T cells do not recognise transplanted material
It tries to attack these cells through host defence system
Patients can be given medication to dampen down CD4 cells and thus , less T killer cells produced and less rejection of transplanted tissues
B LYMPHOCYTES
Release from bone marrow and mature
Stored in the lymphatic system
B cells attached to antibodies but antibodies can’t form antibody antigen complex while still attached to B cells.
So antibodies sit in lymphatic system til required
When required, CD4 cells knock antibodies off B cells.
Antibody-antigen complex forms and phagocytosis of pathogen
Both types of immunity have memory cells - memory T cells recognise the pathogen again and stimulate B cells to produce antibodies rapidly to fight the infection so you don’t get ill
Vaccine
Synthetic version of the antigen causing a virus or infection.
Your body follows the cell mediated and humoral responses to make antibodies against it
Antibodies stored in lymphatic system
If exposed to live virus, antibodies can recognise the foreign antigen, can bind to it and kill it through the immune response
What type of cell is wiped out completely in AIDS?
AIDS wipes out T helper cells CD4+
The HIV virus mutates and destroys T helper cells so it is the wiping out of these cells that makes you likely to catch other infections.
CD8 + cells (T KILLER CELLS)
T killer cells (natural killers)
They work by;
Releasing perforin through autolysis - destruction of cell via enzymes
Releasing lymphotoxin for apoptosis (cell death)
CD4+ cells
T helper cells.
5 functions:
Increase production of T and B cells
Convert CD8 cells into T killer cells
Activates B cells into mature plasma cells
Manages and coordinates immune response
Acts as suppressor cell and slows immune response
B CELLS
B cells mature into plasma cells in bone marrow
B cells activated by T helper CD4 cells and mature into plasma cells
Plasma cells produce immunoglobulins to combine with specific antigen
ANTIBODY ACTION
All People Need Learning Over All
Agglutination- invading organism will stick together and cannot function any more
Precipitation- Antigen-antibody complex formed and is insoluble
Neutralisation- Antibidy binds to pathogen and means it cannot bind to other cells
Lysis- Direct killing of a cell by an antibody
Opsonisation- Antigen marks cells so cells in phagocytosis recognise it quicker to phagocytosis
Activation of complement cascade- enzymes in blood that cause some above processes
Some enhance inflammatory response
Some act as a chemotaxis - cell signalling
Infection
Infection is a complication and extension of inflammatory and immune responses
Infectious disease
A state of tissue destruction resulting from the invasion of micro organisms
Define HOST
Host is the individual exposed to, or contracting, the infection
What is resident flora?
The natural microorganisms that live on or within the body at non-sterile areas without causing harm
Eg: Skin Mucous membranes Bowel Rectum Vagina
Resident flora may be upset by antibiotics as we can kill off that bacteria as well as the harmful one
Eg, thrush
Diarrhoea and sickness
Define pathogen
Disease causing microorganism
What happens in healthy individual ?
Pathogen enters the host
Via skin and mucous membranes
Inflammatory response occurs
Finished and you don’t get ill
If the immune response is weaker or disease is stronger?
If the disease is worse, you may need:
Antibiotics / antivirals
Fluid support
Nutritional support
Steroids
Inadequate immune system
Patients may need organ support
Eg, ventilator
Hypertensives
If infection overwhelming , they may get septicaemia, shock and then death
Clinical signs of feeling unwell
Fever Loss of function Redness Weakness Fatigue Anorexia Cough Pain Lymphadenopathy Purulent exudate - pus formation Nausea Malaise Headache
Pathogens
Bacteria
Viruses
Fungi
Protozoa- motile organisms including parasites
Rickettsiae- intracellular parasites, part bacteria and part virus
Helminths- worms
Mycoplasma - extracellular organisms similar to bacteria and viruses
Diagnostic tests of infection:
- White blood cell count (indicates infection), rises and is non specific
- Serum antibody levels - looking for certain antibodies in high number of a certain infection, eg, TB antibodies Or whooping cough
- Cultures - Pus, antibiotics , grow it on agar to see which bacteria grows on which agar. The one it grows on is that infection.
Then we want to grow culture on antibiotic or antiviral disc to know how to treat it - Sensitivities - sputum analysis
Patients may start on a general antibiotic and then to a specific one - prevents disturbing natural flora too much
