Immune System Flashcards
what is the immune system?
It is the bodies defence against infectious organisms and foreign bodies. Its four main functions are protecting, recognising, attacking and destroying foreign organisms.
What is innate immunity?
This is natural and we are all born with it. Its response is non-specific, it doesn’t matter what enters the body the same response will be generated. Exposure to a pathogen leads to immediate maximal response. There is no immunological memory of what specifically is being attacked.
What is acquired immunity?
It is adaptive, we acquire it over time and it is different for different people depending on what hey have encountered. there is a lag time between exposure and maximal response as specific antibodies need to be generated. Immunological memory takes place.
What are the 5 types of leukocytes (WBCs) that make up the innate arm?
Granulocytes (60-70% of leucocytes in blood) - neutrophil (90% granulocytes); eosinophil (2-5% granulocytes); basophil (0-2% granulocytes)
Agranulocytes - Lymphocyte and monocyte (make up 5-15% of all leucocytes)
What is a neutrophil?
CD16 - undergoes phagocytosis, therefore classed as a polymorphonuclear leucocyte. Most found in bone marrow, some in circulation and the rest in vascular pools. Lifespan in blood 2-6 days, in tissues 2-3 days. Phagocytosis - the bacteria is ingested. Its the initial step of attacking mechanism.
When in the blood capillary, it will flatten against the surface and go through the cell to the antigen. It will engulf it and seal it within the vacuole. Granules swarm the vacuole and fuse, then release killing machinery by degranulation and respiratory burst. The products of the vacuole are emptied.
What is an eosinophil?
Destroys pathogens
What is a basophil?
Causes inflammation
What is a lymphocyte?
They are termed natural killer cells and have markers CD3-, CD16+, CD56+, depending on the specific cell. The immune response is a direct attack or using antibodies. They are intracellular killing cells, as they can kill our own cells if they are infected or mutated as it is programmed to recognise anything foreign. It binds to the surface of infected cell, releases perfornin and activates apoptosis (cell suicide)
What is a monocyte/ macrophage?
CD14 - when it moves from the cell to the blood its called a macrophage. They express a pattern of recognition receptors called toll-like receptors (TLRs) that recognise pathogen - associated molecular pattern. Then the TLR binds, it activated the monocyte/ macrophage. they phagocytose, release messenger substances (cytokines) and become antigen presenting cells (APC) to communicate with the acquired arm.
What are granulocytes and agranulocytes?
Granulocytes have granules throughout their cytoplasm, agranulocytes do not.
What happens if a pathogen gets past the innate arm?
An antigen presenting cell (APC) displays the invading organism to the acquired arm of the immune system in order to activate it. There are 2 APCs, macrophages and dendritic cells. The innate arm is therefore communicating with the acquired arm to try and make a more targeted immune response.
What makes up the acquired arm?
Different types of lymphocytes.
What is MHC2?
Major histocompatibility complex. Formed when APCs incorporate the antigen protein on their cell surface.
What are the different types of lymphocytes in the acquired arm?
Tcells (CD3+) mature in thymus, 60-80% of lymphocytes, have an intracellular response. Type 1 T cell and Type 2 t cells produce different cytokines. Th1 has an intracellular response, and Th2 initiates the extracellular (humoral) response. There are different subsets of T cells also:
- T helpers CD4+ = orchestrate and coordinate the immune response
- T cytotoxins CD8+ = binds to and kills the antigen specific infected cells
- T regulatory CD4+ and CD25+ = regulate/ switch off the immune response to avoid chronic inflammation.
B cells CD19+ and CD20+. mature in bone marrow and make up 5-15% of lymphocytes. They have an extracellular response and produce memory cells. They are only activated and able to bind with the pathogen when a Th2 cell checks the cells. Plasma cells are B cells, they generate specific antibodies that bind to the antigen and trap it, waiting fir a killer cell.
What factors affect the immune system?
gender, age, genetics, vaccination history, obesity, exposure to pathogens, gut flora, smoking, early life events.
