|mmunity Flashcards
What are the physical barriers in innate immunity?
Respiratory tract: mucus and ciliated epithelium
Eyes: tears, lysozyme/lactoferrin
Skin: sweat, antimicrobials, low pH commensal bacteria, skin shredding
GI tract: stomach acidity, intestinal pH, normal flora, mechanical flushing
Genitourinary tract: washing by urine, vaginal secretions, urine acidity, lysozyme
What are the immune tissues?
Appendix Bone marrow Tonsils and adenoids Thymus Spleen Lymph nodes Peyer's patches Lymphatics Blood
Cytokines (interferon) importance in innate immunity
Cell infected with virus produces IFN
IFN acting internally protects infected cell
Secreted IFN binds to receptors on nearby cells and triggers anti-viral response
Natural Killer cells in innate immunity
White blood cells:
- able to recognise and kill infected cells
- NK cell remains unharmed
Phagocytes in innate immunity
Ingest and kill microbes
- Phagocyte attaches to microbe by non-specific receptors
- Phagosome is formed
- Lysosome fuses with phagosome, damages and destroys microbe
- Release of microbial agents
Polymorphonuclear cells Importance in innate immunity
70% neutrophils
- first to arrive at site of infection
- non-dividing, short lived (1 day)
- granulated = chemical attack
Signs of inflammation
Erythema (redness) Heat Swelling/oedema Pain Possible loss of function Widespread systemic inflammation may lead to septic shock & death.
Inflammation in innate immunity
Causes:
- vasodilation and increased permeability
- accumulation of blood
- leakage of clotting factors
- chemotaxis of neutrophils/ macrophages
- death of phagocytes
- initiation of tissue repair
Fever in innate immunity
High temperate triggered by resetting hypothalamic thermostat
- triggered by cytokines/toxins
- inhibits bacterial growth
- speeds up some enzyme reactions aiding tissue repair
Adaptive immunity
A dedicated system of tissues, cells and molecules that act
in concert to provide specific immune responses:
> memory
> specificity
LYMPHOCYTES = cells of adaptive immunity response
clonal selection and memory
B cells and antibody-mediated immunity
T cells and cell-mediated immunity
Describe the adaptive defence system
Two types of lymphocytes:
- B lymphocytes (B cells)
- T lymphocytes ( T cells)
Cells recognise pathogens using cell-surface receptors
Each has a unique binding site for a different epitope
Only those lymphocytes that are specific for components of infecting pathogen are selected
→ divide, proliferate & differentiate into effector lymphocytes
→ some proliferate into memory lymphocytes
Describe T lymphocytes
Kill virus-infected cells (cytotoxic T cells)
Activate macrophages
Help antibody responses ( T helper cells)
Immunoregulatory function
What are the two types of T cells?
CD8 or CD4 glycoprotein markers
- both have T cell receptors that recognise antigens
- T cell receptors recognise peptide antigens presented on surface of innate immune system cells eg. macrophages
- antigen needs to be presented bound to MHC molecules: 2 classes
> MHC class 1 - on all cells with a nucleus ( not RBC)
> MHC class 11 - on professional antigen presenting cells (APCs)
MHC1 present antigens of intracellular origin eg. viral proteins to CD8 cells = cytotoxic T cells
MHC11 present antigens of extracellular origin eg. from bacteria to CD4 T cells = differentiate into T helper cells:
- activate macrophages
- help B cells become antibody producing plasma cells
What is SCID?
Affects lymphocytes
- failure to thrive
- viral gastroenteritis
- viral chest infection
- parasitic chest infection
- bacterial septicaemia
- fungal urinary infection
What is DiGeorge syndrome
- decreased or absent T cell numbers and function
- variable antibody function:
> IgM normal to low
> IgG low to absent - increase susceptibility to vial, fungal infections
