- trigger the recruitment of inflammatory cells.
and function within the immune system by identifying and eliminating pathogens that might cause infection.Mast cells are a type of innate immune cell that reside in connective tissue and in the mucous membranes. DELL XPS M1530 CPU FAN They are intimately associated with defense against pathogens and wound healing, but are also often associated with allergy andanaphylaxis. When activated, mast cells rapidly release characteristic granules, rich in histamine and heparin, along with various hormonal mediators, and chemokines, or chemotactic cytokines into the environment. DELL XPS M170 CPU FAN
Histamine dilates blood vessels, causing the characteristic signs of inflammation, and recruits neutrophils and macrophages.The word 'phagocyte' literally means 'eating cell'. These are immune cells that engulf, i.e. phagocytose, pathogens or particles. DELL XPS M1710 CPU FAN
To engulf a particle or pathogen, a phagocyte extends portions of its plasma membrane, wrapping the membrane around the particle until it is enveloped (i.e. the particle is now inside the cell). Once inside the cell, the invading pathogen is contained inside an endosome which merges with a lysosome. Compaq Presario CQ42-228LA Laptop Keyboard
The lysosome contains enzymes and acids that kill and digest the particle or organism. Phagocytes generally patrol the body searching for pathogens, but are also able to react to a group of highly specialized molecular signals produced by other cells, called cytokines. The phagocytic cells of the immune system include macrophages, neutrophils, and dendritic cells. HP Pavilion dm1-1010st Laptop Keyboard
Phagocytosis of the hosts’ own cells is common as part of regular tissue development and maintenance. When host cells die, either internally induced by processes involving programmed cell death (also called apoptosis), or caused by cell injury due to a bacterial or viral infection, phagocytic cells are responsible for their removal from the affected site. DELL 454RX Laptop Keyboard
By helping to remove dead cells preceding growth and development of new healthy cells, phagocytosis is an important part of the healing process following tissue injury.
Macrophages, from the Greek, meaning "large eaters," are large phagocytic leukocytes, SAMSUNG R522 Laptop Keyboard
which are able to move outside of the vascular system by moving across the walls of capillary vessels and entering the areas between cells in pursuit of invading pathogens. In tissues, organ-specific macrophages are differentiated from phagocytic cells present in the blood called monocytes. Compaq Presario CQ57 Series Laptop Keyboard
Macrophages are the most efficient phagocytes, and can phagocytose substantial numbers of bacteria or other cells or microbes. The binding of bacterial molecules to receptors on the surface of a macrophage triggers it to engulf and destroy the bacteria through the generation of a “respiratory burst”, causing the release of reactive oxygen species. TOSHIBA Satellite L755D-SP5165RM Laptop Keyboard
Pathogens also stimulate the macrophage to produce chemokines, which summons other cells to the site of infection.
Neutrophils, along with two other cell types; eosinophils and basophils (see below), are known as granulocytes due to the presence of granules in their cytoplasm, or as polymorphonuclear cells (PMNs) due to their distinctive lobed nuclei. SAMSUNG NP-Q320-FS01UK Laptop Keyboard
Neutrophil granules contain a variety of toxic substances that kill or inhibit growth of bacteria and fungi. Similar to macrophages, neutrophils attack pathogens by activating a respiratory burst. The main products of the neutrophil respiratory burst are strong oxidizing agents including hydrogen peroxide, free oxygen radicals and hypochlorite. HP G42-364LA Laptop Keyboard
Neutrophils are the most abundant type of phagocyte, normally representing 50 to 60% of the total circulating leukocytes, and are usually the first cells to arrive at the site of an infection. The bone marrow of a normal healthy adult produces more than 100 billion neutrophils per day, and more than 10 times that many per day during acute inflammation. HP AESP7U00110 Laptop Keyboard
Dendritic cells (DC) are phagocytic cells present in tissues that are in contact with the external environment, mainly the skin (where they are often calledLangerhans cells), and the inner mucosal lining of the nose, lungs, stomach and intestines. They are named for their resemblance to neuronal dendrites, but dendritic cells are not connected to the nervous system. HP G61-425ES Laptop Keyboard
Dendritic cells are very important in the process of antigen presentation, and serve as a link between the innate and adaptive immune systems.
Basophils and eosinophils are cells related to the neutrophil (see above). When activated by a pathogen encounter, basophils releasinghistamine are important in defense against parasites, and play a role in allergic reactions (such as asthma). HP 640436-001 Laptop Keyboard
Upon activation, eosinophils secrete a range of highly toxic proteins and free radicals that are highly effective in killing bacteria and parasites, but are also responsible for tissue damage occurring during allergic reactions. Activation and toxin release by eosinophils is therefore tightly regulated to prevent any inappropriate tissue destruction. Lenovo 3000 N200 Laptop Keyboard
Natural killer cells, or NK cells, are a component of the innate immune system which does not directly attack invading microbes. Rather, NK cells destroy compromised host cells, such as tumor cells or virus-infected cells, recognizing such cells by a condition known as "missing self." DELL XPS 15 L502X Laptop Keyboard
This term describes cells with low levels of a cell-surface marker called MHC I (major histocompatibility complex) - a situation that can arise in viral infections of host cells. They were named "natural killer" because of the initial notion that they do not require activation in order to kill cells that are "missing self." IBM Lenovo ThinkPad R51 1833 Laptop Keyboard
For many years it was unclear how NK cell recognize tumor cells and infected cells. It is now known that the MHC makeup on the surface of those cells is altered and the NK cells become activated through recognition of "missing self". Normal body cells are not recognized and attacked by NK cells because they express intact self MHC antigens. HP G62-a20EJ Laptop Keyboard
Those MHC antigens are recognized by killer cell immunoglobulin receptors (KIR) which essentially put the breaks on NK cells. The NK-92 cell line does not express KIR and is developed for tumor therapy.
Like other 'unconventional' T cell subsets bearing invariant T cell receptors (TCRs), ACER Aspire 5742 Laptop Keyboard
such as CD1d-restricted Natural Killer T cells, γδ T cells exhibit characteristics that place them at the border between innate and adaptive immunity. On one hand, γδ T cells may be considered a component of adaptive immunityin that they rearrange TCR genes to produce junctional diversity and develop a memory phenotype. HP Pavilion DV7-3186cl laptop keyboard