In this video I go over the mainstream theory of the immune system, which is a network of biological processes that detects and responds pathogens entering an organism. Nearly all organisms have some sort of immune system, while jawed vertebrates (including humans) have sophisticated defense mechanisms and the ability to adapt to recognize previously encountered pathogens. The innate immune system is a rapid and broad defense mechanism, which includes phagocytosis to engulf large foreign particles. The adaptive immune system involves specialized white blood cells (killer cells and T / B lymphocytes) which can recognize unique molecules on pathogens (called antigens) via Y-shaped proteins called antibodies. This immunological memory is the basis of vaccination.
Immune system is a biological network that detects and responds to pathogens: 0:00
Diagram of phagocytosis, in which a cell uses its plasma membrane to engulf a large particle: 1:58
Complement system or complement cascade enhances or complements the ability of antibodies and phagocytic cells to clear microbes. It consists of small proteins circulating in the blood as inactive precursors: 3:18
Cytokines are small proteins important in cell signalling and cannot cross the lipid bilayer of cells. Similar to hormones: 8:23
Inflammation is a protective response to harmful stimuli and its function is to eliminate the initial cause of cell injury and clear out damaged tissues to initiate tissue repair. 12:55
Jawed vertebrates have the ability to adapt to recognize pathogens more efficiently, and is the basis of vaccination: 17:47
Diagram of immune response for first exposure and reinfection: 19:47
Structure of a long bone. Bones are the primary site of new blood cell production including, lymphocytes, a type of white blood cell involved in the adaptive immune system : 23:55
Antibody (Ab) or immunoglobulin (Ig) is a Y-shaped protein that identifies and neutralizes foreign objects. It recognizes a unique molecule on the pathogen, called an antigen (Ag or antibody generator).: 27:28
Thymus is a primary lymphoid organ in which Thymus cell lymphocytes or T cells mature. It is located in the upper front part of the chest.: 32:43
Scanning electron micrograph of a red blood cell, platelet, and a T-lymphocyte: 34:23
B cells or B lymphocytes are a type of white blood cell in the humoral immunity component of the adaptive immune response, which is mediated by macromolecules found in extracellular fluids: 34:54
Transmission electron micrograph of a human B cell: 42:15
Bursa of Fabricius is the site of hematopoiesis or blood cell production in birds. B cells derive their name from this and not from bone marrow, as is commonly misunderstood today: 42:42
Diagram of different blood cells derived from hematopoietic stem cells: 46:20
Memory B cell (MBC) circulate in the blood stream in a quiescent or inactive state and functions to memorize characteristics of an antigen that activated their parent B cell during infection. If it later encounters the same antigen, it triggers an accelerated secondary immune response: 49:34
Memory T cells might have some of the same functions as memory B cells: 52:04
Diagram of the primary immune response: 52:36
Macrophages (Greek for large eaters) are a type of white blood cell that engulfs and digests anything that does not have specific healthy surface proteins: 55:01
