Chapter 1: An overview Flashcards
Cells of the innate immune system
Adaptive immune cells: (lymphocytes)
- B cell
- Helper T cell
- Killer T cell
Innamte immune cells:
- NK cell (lymphocyte)
- Dendritic cell
- Macrophage
- Neutrophil
- Eosinophil
- Mast cell
- Megakaryocyte
- Red Blood Cell (Erythrocyte)
Macrophage
Found under the skin, in lungs and intestine. Made in the bone marrow from stem cells: monocytes that mature in the tissue. Immediately crawls to the compound that sends out danger molecules.
- Phagocytosis: creates a phagosome (vesicle) –> fuses with lysosome (contains chemicals & enzymes that destroy the compound).
- Give off chemicals –> increases blood flow to the wound, fluid will leak into tissue and nerve cells stimulated signalling pain
- Produce and secrete cytokines
Cytokines
Hormone like messengers that facilitate communication between immune cells, send out into the blood
Natural Killer (NK) cells
Found in blood, spleen or liver (stores blood); ‘on call’. Can destroy bacteria, parasites, virus infected cells and some cancer cells. Made and matured in the bone marrow; half life of a week.
Antibody
Produced by B cells when an antigen is present. Immunoglobulin G (IgG) (75%), IgA, IgD, IgE and IgM.
Structure:
- Fab-regions: two identical ‘hands’ that bind to a specific antigen (light chains)
- Fc-region (constant region): binds to receptors –> determines the class (heavy chain)
Diversity of antibodies
Mature antibody genes are made by modular design.
- In every B cell (encoding the heavy chain), there are multiple copies of 4 gene segments (V, D, J and C) –> recombination
- DNA encoding the light chain also assembled by gene segments.
- Junctional diversity: in joining gene segments, DNA bases can de added or deleted
How B cells produce antigens
Invader –> more of appropriate B cells are made. They prevent entering the cell or reproducing once it’s entered (neutralizing antibodies).
Clonal selection:
- B cell receptors (BCRs): batch of antibodies made –> surface
- Cognate antigen: BCRs waiting for antigen that fits –>
- Proliferation: cloning
- Opsonize: identify invaders
- Bind with Fab-region; Fc-tail binds to Fc-receptors on macrophages or other destroying cells –> focus on invaders
T cell
Have T-cell receptors (TCRs) on the surface and have clonal selection; proliferation takes a week.
- Matures in thymus
- Specializes in recognizing protein antigens
- Receptors remain on surface
- Can only recognize an antigen when it is properly presented
3 types of T cells
- Killer T cell: cytotoxic lymphocytes (CTLs) can destroy virus infected cells
- T helper cell: directs action by secreting cytokines like IL-2 and IFN-y
- Regulatory T cell: keeps immune system from overreacting
Antigen presentation
Using major histocompatibility complex (MHC); involved in matching blood types
- Class I MHC: billboards which presents peptides to killer T cells to show what’s going on in the cell; made by nucleated cells (worst in het broodje)
- Class II MHC: billboards for T helper cells that display problems that exist outside the cell; made by antigen presenting cells (APCs) (worst buiten het broodje)
Activation of the adaptive immune system
Co-stimulation (also applies to B-cells and killer T cells):
- Class II MHC presents an antigen which is recognized as cognate antigen by T helper cell
- Non-specific protein on surface of APC plugs into its receptor of T helper cell
–> Proliferation into many Th cells –> mature into cytokine producing cells
Lymphatic system
Secondary lumphoid organs (SLOs), like lymph nodes, drain fluid (lymph) that leaks out of our blood vessels into the tissue.
- Lymph collected from lower body into lymphatic vessels and moves by muscular contraction to upper torso
- Collected in thoracic duct
- Emptied in subclavian vein and recycled into the blood
- Passes lymph nodes: immune cells and antigens meet
