Helicobacter and Macrophages Study - Research Paper Example

Helicobacter and Macrophages Study Background to the paper This study aimed at determining whether macrophages are required at the time of challenge for vaccination to be successful. There have been some studies done previously on the subject that included the ones which showed that depletion of macrophages led to reduced inflammation in H. pylori infected C57 BL/6 mice (Kaparakis et al., 2008). When mice were depleted during the vaccination process with a CT based vaccine, shows the unpublished study, there was no significant effect on the efficacy of vaccination. Besides this both vaccinated and control mice showed similar gastritis scores, which is indicative of the presumption that there is no need for macrophages to be present for effective presentation of H.pylori antigen in the presence of an adjuvant. They are also not required for mounting a gastritic infiltrate or an antibody response. The protocol of this experiment was to vaccinate mice with H. pylori antigen and CT, or as recommended by Kaparakis et al (2008) and Becher et al., (2002) the S. typhimurim based vaccine to check if macrophages are required for the effector stage of the protective response. Concurrently and as again recommended by Kaparakis et al, one week before and after challenge mice will be subjected to liposomes loaded with Cl2MDP. This will determine the efficacy of the vaccination. Since this experiment envisions deducing conclusions on vaccination effective against H. pylori, it becomes pertinent to understand the bacteria in its entirety and also look into macrophages, as to what they are and what and how they are capable of doing what they do. H. pylori Brief introduction Helicobacter pylori or H. pylori, a helix-shaped bacterium was previsuly known as Campylobacter pyloridis. It is found in stomach, is Gram-negative and mircoaerophilic. It history is just three decades old as it was identified by Robin warren and Barry Marshall, both Australian sceintists. They came across the bacterium during their research on gastric ulcers and chronic gastritis. It is interesting to note that both these conditions were previously linked to anything but microbes. People in developing countries harbour infection more than those in the developed nations, even as a little over 50 percent of the world's population harbours the bacterium mostly in the upper gastrointestinal tract (Yoshio, 2008). Blaser (2006) has stated that it may as well be responsible for the development of stomach's natural ecology. The bad part of H. pylori is that it has diverse number of strains. Tomb et al., (1997) and Oh et al., (2006) have stated that of all these strains genomes of three of them have already been sequenced completely. For example, genome of a particular strain contains base pairs to the tune of about 1.7 million and number of genes at 1,550. The genetic part of H. pylori is being investigated to under how it works pathogenically and how it becomes so potent to do widespread gastric damage. How does the microb work? One gene sequence that is said to give this bacterium deadly power to create damage is a particular gene sequence called Cag pathogenecity island. The sequenced strains (two of the three) have shown a 40-kb-long Cag pathogenicity island. This contains as many as 40 genes but is generally not found in H. pylori-infected humans who are asymptomatic despite the infection. In order to attack, H. pylori has to first adapt to the stomach's acidic environment, particularly that of lumen. It has to search for a better and conducive environment to sustain and thrive; an environment that has neutral pH, which it finds in the epithelial cells below the lumen. The bacterium uses its flagella to burrow into that space until it reaches the correct pH gradient which it is bale to sense through its internal mechanism. This process, which is called chemotaxis, also makes it possible for the bacterium to avoid being swept away in the gut. Schreiber et al., (2004) have remarked that the bacterium moves away from the site of its creation to a safer epithelial environment along with its mucus environment. Sometimes it even proliferates into the epithelial cells by way of adhesions, a process helping it to get bound to carbohydrates and lipids in the epithelial cell membrane (Peterson et al., 2003). Several mechanisms are used by H. pylori to harm the duodenal lining and stomach. In order to regulate pH, it produces ammonia and other biochemicals - both are toxic to epithelial cells. The biochemicals include some phospholipases, vacuolating cytotoxin A (VacA) and proteases. The site where H. pylori infects gets inflammation as the bacterium colonizes at the site. This results in chronic gastritis. The immune response, which causing inflammation, is generally triggered by what are known as Hcps or Helicobacter cysteine-rich proteins. Subsequent to this pepsin, which is a digestive enzyme and stomach acid overwhelm meant to protect stomach, resulting in duodenal and other ulcers in the stomach. Dixon (2000) has suggested that it is the acidity levels of stomach that determine where does H. pylori colonize. It colonizes near pyloric antrum in the stomach, which is the site of duodenum's exit to stomach, where H. pylori colonize in case of people having high stomach acid concentrations. Those who do not have as much stomach acid can have H. pylori concentrate almost everywhere else. The investigation into H. pylori working in human body continues and cancer research vis-a-vis H. pylori infection forms a major component of this investigation. It is believed that at the site of H/ pylori colonization there is an increased free radical production, which works either in conjunction or isolation of increased mutation of host cells. Tsuji et al., (2003) have also talked of perigenetic pathway, which triggers host cell protein alterations. H. pylori have been implicated in inducing high levels of interleukin 6 and TNF-α. Recent research suggests that TNF-α can help mutated cells to disperse even if no additional mutations take place in the epithelial cells. The H. pylori colonization and the increased acid load in the stomach are enough to trigger damage, particularly in the duodenum, by way of atrophy and related conditions. Macrophages Brief introduction When tissue monocytes undergo differentiation, macrophages are produced. A Russian bacteriologist, Illya Mechnikov discovered macrophages in 1884. Both macrophages and monocytes are phagoctyes and the latter are said to trigger certain defense mechanisms termed as adaptive immunity. They also provide innate immunity or non-specific defense. Their primary role is to engulf pathogens, digest them and also the cellular debris surrounding the same. It is in light of this hypothesis that this experiment was conducted; to see whether or not they provide any impetus to vaccination for being successful. There role has also been documented in stimulating immune cells and lymphocytes so that they are able to fight infection due to pathogens. Termed as phagocytic cells, their primary targets are infectious microbes, any foreign substance and ever carcinogenic cells. They induce either destruction or ingestion of all these. Present in all living tissues, they are also capable of regeneration. Functions Their functions are widely seen in i) pahagocytosis, ii) in adaptive immunity, iii) in muscle regeneration, iv) in limb regeneration, and V) in iron homeostasis. Pahagocytosis plays a dominant role in chronic inflammation are their speciality lies in quick removal of dead cell debris. This has a great connection with neutrophil granulocytes, which is prevalent in early inflammation. macrophages ingest them readily. The attack on neutrophils is normally mounted by fixed macrophages; ready for the offensive anywhere in the neural, liver, lung, spleen or even connective tissues. As these start engulfing pathogens and any foreign bodies, new macrophages get reinforced into the act. On ingestion phagosome traps a pathogen, only to fuse with a lysosome at the end. Research has suggested that average 100 bacteria are digested by macrophages before they crumble under their own compounds released during digestion of microbes. Their role in adaptive immunity is laudable as they act as body's superior defense system by expelling debris and worn-out cells. The immune response they initiate is crucial in maintaining general health of the body. They also provide defense against somatic cells infected with parasites and fungus and also tumor cells. Their role in muscle regeneration has been attributed to their "two waves" working simultaneously. One wave works immediately at the onset of any injury and the second wave that is beneath it stay active for many days at the site which is regenerating (St Pierre and Tidball, 1994). Tidball and Wehling-Henricks (2007) demonstrated their muscle regeneration activity on mice, particularly their solus muscle. In order to prove their muscle regeneration capability, the researchers conducted their experiments on two muscle sets; injured muscle with no macrophage concentration and non-injured muscle having macrophage concentration. The muscle having depleted macrpophages did not show significant growth, while as the one with high concentration did show significant re-growth. That clearly indicates that if there is macrophage depletion when muscles are expected to grow, they won't show any significant improvement. The limb generation experiments have been conducted on salamanders. Studies have revealed that muscle regeneration is promoted by macrophages mainly between day 2 and 4 by inducing myonuclei reduction. They also facilitate iron homeostasis in the body by their continual process of debris and dead cell removal. The liver and spleen are two sites where erythrocytes are continually destroyed by macrophage action after their average 120 day live span. During intake of parenteral iron, macrophages have a tendency to engulf macromoelcules, thus playing a crucial role in pharmacokinetics. Macrophages are strategically located in the human body. These locations are the ones where chances of microbial invasion are the maximum. Macrophages are named depending on the sites at which macrophages are located. For example, alveolar macrophages refer to ones located in lungs or pulmonary alveolus. Those in connective tissues are named histiocytes, Kupffer cells in liver, microgalia in neural tissue, osteoclasts in bones, Hofbauer cells in placenta, sinusoidal lining cells in spleen, giant cells in connective tissues, peritoneal macrophages in peritoneal cavity and adipose tissue macrophages in adipose tissues. Antibiotics and H.pylori Microbes are generally perceived by lay public as organisms that cause disease, which is not the case in reality. Microbes are a blanket term used for bacteria, viruses, fungi, yeasts and parasites. Bacteria, again, can be harmful and harmless; both residing in the human body. H. pylori are a harmful microbe. Antibiotics cannot be deemed as 'cure all' therapies as while they work effectively on some parasites and bacteria, they do not offer any significant resistance to fungi and yeasts. That apart, there are some possible problems associated with antibiotics. These include possible side-effects, which are quite common, if not serious. Though that should not be construed as a statement which means antibiotic use is free from any serious consequences. The bad part is that when antibiotics are ingested in the body, which is in a diseased state, they also kill the normal defense shield while killing the pathogens. This is one reason why research is going to see the need for macrophages to stay in an optimum state during therapy; either vaccination or antibiotic. Effective antibiotic therapy exists against H. pylori but recently research has shifted its focus towards development of vaccines against this Gram-negative pathogen. This is keeping in view the severity of H. pylori infection. Research so far has yielded encouraging results particularly in the wake of identification of proteins like urease, cytotoxin-associated antigen, vacuolating cytotoxin and neutrophil-activating protein. Vaccines have been showing promising results in providing protection against H. pylori according to experiments conducted on animal models. Even though the exact effector mechanism through which vaccines exert a protective mechanism against H. pylori still remains to be understood properly, the next few years are supposed to provide a deeper insight into their action on the pathogen. Seeing the macrophage link between vaccine-macrophage-pathogen triad is one such effort at reaching better understanding on the research. In this regard the scientific world foresees several animal and human trials to answer some pertinent question on host-microbe interactions in H. pylori problem. References Becher, D., Deutscher, M. E., Simpfendorfer, K. R., Wijburg, O. L., Pederson, J. S., Lew, A. M., et al. (2010). Local recall responses in the stomach involving reduced regulation and expanded help mediate vaccine-induced protection against Helicobacter pylori in mice. European Journal of Immunology, 40(10), 2778–2790. Blaser, M. J. (2006). "Who are we? Indigenous microbes and the ecology of human diseases". EMBO Reports 7 (10): 956–60. Giudice et al., (2009). Development of vaccines against Helicobacter pylori. Expert Rev Vaccines. 2009 Aug;8(8):1037-49. Kaparakis, M. M., Laurie, K. L. K., Wijburg, O. O., Pedersen, J. J., Pearse, M. M., van Driel, I. R. I., et al. (2006). CD4+ CD25+ regulatory T cells modulate the T-cell and antibody responses in helicobacter-infected BALB/c mice. Infection and Immunity, 74(6), 3519–3529. doi:10.1128/IAI.01314-05 Kaparakis, M., Walduck, A. K., Price, J. D., Pedersen, J. S., van Rooijen, N., Pearse, M. J., et al. (2008). Macrophages are mediators of gastritis in acute Helicobacter pylori infection in C57BL/6 mice. Infection and Immunity, 76(5), 2235–2239. doi:10.1128/IAI.01481-07. Oh J.D., Kling-Bäckhed H, Giannakis M et al. (June 2006). "The complete genome sequence of a chronic atrophic gastritis Helicobacter pylori strain: Evolution during disease progression". Proc Natl Acad Sci U.S.A. 103 (26): 9999–10004. St Pierre B.A., JG Tidball (1994). "Differential response of macrophage subpopulations to soleus muscle reloading following rat hindlimb suspension". Journal of Applied Physiology 77 (1): 290–297. Tidball J.G., Berchenko E, Frenette J (1999). "Macrophage invasion does not contribute to muscle membrane injury during inflammation". Journal of Leukocyte Biology 65 (4): 492–498. Tsuji S, Kawai N, Tsujii M, Kawano S, Hori M (July 2003). "Review article: inflammation-related promotion of gastrointestinal carcinogenesis--a perigenetic pathway". Aliment. Pharmacol. Ther. 18 (Suppl 1): 82–9. Tomb J.F., White O, Kerlavage A.R., et al. (August 1997). "The complete genome sequence of the gastric pathogen Helicobacter pylori". Nature 388 (6642): 539–47. Yoshio, Y., (2008). Helicobacter pylori: Molecular Genetics and Cellular Biology. Caister Academic Pr. Read More

Several mechanisms are used by H. pylori to harm the duodenal lining and stomach. In order to regulate pH, it produces ammonia and other biochemicals - both are toxic to epithelial cells. The biochemicals include some phospholipases, vacuolating cytotoxin A (VacA) and proteases. The site where H. pylori infects gets inflammation as the bacterium colonizes at the site. This results in chronic gastritis. The immune response, which causing inflammation, is generally triggered by what are known as Hcps or Helicobacter cysteine-rich proteins.

Subsequent to this pepsin, which is a digestive enzyme and stomach acid overwhelm meant to protect stomach, resulting in duodenal and other ulcers in the stomach. Dixon (2000) has suggested that it is the acidity levels of stomach that determine where does H. pylori colonize. It colonizes near pyloric antrum in the stomach, which is the site of duodenum's exit to stomach, where H. pylori colonize in case of people having high stomach acid concentrations. Those who do not have as much stomach acid can have H.

pylori concentrate almost everywhere else. The investigation into H. pylori working in human body continues and cancer research vis-a-vis H. pylori infection forms a major component of this investigation. It is believed that at the site of H/ pylori colonization there is an increased free radical production, which works either in conjunction or isolation of increased mutation of host cells. Tsuji et al., (2003) have also talked of perigenetic pathway, which triggers host cell protein alterations. H. pylori have been implicated in inducing high levels of interleukin 6 and TNF-α.

Recent research suggests that TNF-α can help mutated cells to disperse even if no additional mutations take place in the epithelial cells. The H. pylori colonization and the increased acid load in the stomach are enough to trigger damage, particularly in the duodenum, by way of atrophy and related conditions. Macrophages Brief introduction When tissue monocytes undergo differentiation, macrophages are produced. A Russian bacteriologist, Illya Mechnikov discovered macrophages in 1884. Both macrophages and monocytes are phagoctyes and the latter are said to trigger certain defense mechanisms termed as adaptive immunity.

They also provide innate immunity or non-specific defense. Their primary role is to engulf pathogens, digest them and also the cellular debris surrounding the same. It is in light of this hypothesis that this experiment was conducted; to see whether or not they provide any impetus to vaccination for being successful. There role has also been documented in stimulating immune cells and lymphocytes so that they are able to fight infection due to pathogens. Termed as phagocytic cells, their primary targets are infectious microbes, any foreign substance and ever carcinogenic cells.

They induce either destruction or ingestion of all these. Present in all living tissues, they are also capable of regeneration. Functions Their functions are widely seen in i) pahagocytosis, ii) in adaptive immunity, iii) in muscle regeneration, iv) in limb regeneration, and V) in iron homeostasis. Pahagocytosis plays a dominant role in chronic inflammation are their speciality lies in quick removal of dead cell debris. This has a great connection with neutrophil granulocytes, which is prevalent in early inflammation.

macrophages ingest them readily. The attack on neutrophils is normally mounted by fixed macrophages; ready for the offensive anywhere in the neural, liver, lung, spleen or even connective tissues. As these start engulfing pathogens and any foreign bodies, new macrophages get reinforced into the act. On ingestion phagosome traps a pathogen, only to fuse with a lysosome at the end. Research has suggested that average 100 bacteria are digested by macrophages before they crumble under their own compounds released during digestion of microbes.

Their role in adaptive immunity is laudable as they act as body's superior defense system by expelling debris and worn-out cells.

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