Innate immune system cells and their functions


Phagocytic cells are a component of the innate immune system, and consist of monocyte macrophages, polymorphonuclear leukocytes, and eosinophils. These cells mature in the bone marrow, circulate in the blood for a short time as mature cells, and enter the tissue spaces by diapedesis through capillary walls, in response to cytokines and chemotactic factors.

Macrophages play a central role in the innate immune response. Derived from the blood monocytes, they circulate for a couple of days in the blood and then leave the vascular compartment to become active tissue macrophages. Macrophages possess receptors for carbohydrates, like mannose, that aren't normally found on the cells of vertebrates. This allows the macrophages to discriminate self from nonself. Receptors for antibodies and complement are found on both neutrophils and macrophages.

This adaptation allows for enhanced phagocytosis of foreign organisms coated with antibody or complement. Macrophages have the following essential functions: chemotaxis (cell movement), phagocytosis, and most significant of all, processing and presentation of antigen in an immunogenic form recognizable to T lymphocytes.

Microorganisms engulfed by macrophages can be destroyed when they encounter a wide range of toxic intracellular molecules produced by macrophages. Some of these molecules include superoxide anion, hydroxyl radicals, hypochlorous acid, nitric oxide, plasma proteins and peptides, lysozyme, arachidonic acid metabolites, nucleotide metabolites, and cytokines. Numerous tissue-specific cells are of macrophage lineage and function to procedure and present antigen.

Polymorphonuclear leukocytes originate from pluripotent bone marrow stem cells. These cells circulate in the blood and tissue, and their main function is phagocytosis and destruction of foreign antigens. These cells function in an antigen-nonspecific style, and have receptors for antibodies as well as for complement, so that if microorganisms are coated with either of these components, phagocytosis will probably be enhanced.

Eosinophils, often found in inflammatory sites or at websites of immune reactivity, play a role in host defense against parasites along with other large metazoan pathogens. Even though eosinophils show certain functional characteristics comparable to those of neutrophils, they are only weakly phagocytic. One proposed mechanism for their ability to kill parasites is by way of the release of cationic proteins and reactive oxygen metabolites into extracellular fluid. In addition to releasing mediators, eosinophils also possess the capability to synthesize and secrete prostaglandins, leukotrienes, and various cytokines.

Eosinophils seem to have a modulatory or regulatory function in numerous kinds of inflammation. Nevertheless, in the airway inflammatory response in asthma, eosinophil-derived mediators of inflammation, including major fundamental protein (MBP), eosinophil-derived neurotoxin (EDN), eosinophil cationic protein (ECP), and lysophospholipase (LPL) are toxic to respiratory epithelium.

Therefore, in certain instances, eosinophils promote tissue injury, and in this particular instance, contribute to the pathogenesis of allergen-triggered inflammation in diseases such as asthma. The precise mechanism by which eosinophils trigger oxidative damage isn't recognized. Bromide ion is thought to be a substrate for eosinophil peroxidase, and eosinophil oxidative damage may happen by way of bromination of tyrosine residues.

Legal Disclaimer

Our website is not responsible for the information contained by this article. Webworldarticles.com is a free articles resource thus practically any visitor can submit an article. However if you notice any copyrighted material, please contact us and we will remove the article(s) in discussion right away.


This article was sent to us by: Paula Lappin at 01182011

Related Articles

1. Chemoprotective effects of anthocyanin found in berries
Anthocyanins have been shown to exhibit anticarcinogenic activity against multiple cancer cell types in vitro, and the mechanism of action seems to be rather complex. I...

2. Anthocyanins induce apoptosis in several cancer cell types
Apoptosis Induction In addition to the uncontrolled cell proliferation, resistance to apoptosis (programmed cell death) is another important hallmark of cancer ...

3. Daily intake of anthocyanins can protect against different cancers
Although the information is still limited, available information indicates that dietary intake of anthocyanins or anthocyanin-rich food can protect against different canc...

4. Ursolic acid inhibits the proliferation of various tumor cell lines
The in vitro anti-tumor activity of ursolic acid was reviewed in 2001. In addition to its anti-inflammatory activity, ursolic acid reduces the proliferation of many tumor...

5. Effects of berries on the RTK pathways and their chemoprevention
Although large numbers of studies have reported that RTKs are important in carcinogenesis, the research on the potential of targeting RTKs by berry extracts is still in ...

6. Differences in phenolic content and antioxidant activity of berries
Significant differences in phenolic content and antioxidant activity among different parts of berry fruits were reported. Therefore, correlations among phenolics, antio...

7. Tobacco alcohol and dietary habits as esophageal cancer risk factors
Tobacco and alcohol are well established risk factors for esophageal SCC, increasing risk by 3 to 8 and 3 to 5-fold, respectively. In contrast, alcohol consumption appear...

8. Prevention of skin malignancies with daily berry intake
The skin is the largest organ of the human body. It is responsible for acting as both a barrier and a regulating influence between the outside world and the environment w...

9. Health benefits of pomegranates also include cancer prevention
The pomegranate fruit has an ancient history and is mentioned in many Holy Scriptures such as the Torah, the Bible, and the Quran. For centuries, the fruit has been revered...

10. Prevention and treatment of colon cancer with pomegranates
The effect of pomegranate seed oil (PGO) was studied in mice on the occurrence of colonic aberrant crypt foci (ACF) induced by azoxymethane. Colonic tumors were induced i...