Immune responses consequences

The consequence of ADA deficiency is accumulation of adenosine and 2 -deoxyadenosine, substances toxic to lymphocytes, important cells in the immune response. 2 -Deoxyadenosine is particularly toxic because its presence leads to accumulation of its nucleotide form, dATP, an essential substrate in DNA synthesis. Elevated levels of dATP actually block DNA replication and cell division by inhibiting synthesis of the other deoxynncleoside 5 -triphosphates (see Chapter 27). Accumulation of dATP also leads to selective depletion of cellular ATP, robbing cells of energy. Children with ADA SCID fail to develop normal immune responses and are susceptible to fatal infections, unless kept in protective isolation. 

Apart from offering a new and highly specific approach to the inhibition of herpesviruses, this new mechanism of action could potentially also have beneficial immunological consequences. During treatment with BAY 38-4766, viral protein synthesis continues, but due to the lack of monomeric genomic length DNA, only empty particles (dense bodies) can be formed. It is conceivable that these non-infections viral particles could aid the establishment of an antiviral immune response, leading to better control of the virus by the host. This mechanism appears... 

The morbidity and mortality that are often associated with human GI helminth infections reflect in part the nutritional consequences of diarrhoea and malabsorption, and the resulting malnutrition that can accentuate the effects of infection by suppressing the protective immune response as well as compromising intestinal repair (Ferguson et al., 1980 Keymer and Tarlton, 1991 Cooper et al, 1992). In experimental rodents the pathology associated with infection is characterized by villus atrophy, crypt hyperplasia, goblet cell hyperplasia and infiltration of the mucosa by a variety of... 

Finally, a particularly interesting ongoing challenge will be to understand the potential for do-it-yourself immune stimulation to have unintended consequences. There are now many herbal supplements, functional foods and other over-the-counter products that promise to boost the immune response and most are considered to be safe for use by the general public. Although there is limited published evidence of adverse immune system effects of these materials, some have been associated with autoimmunity [95,96], See chapter 11 for a detailed discussion of the beneficial and potential adverse effects of nutraceuticals and functional foods. 

In addition to suppressive effects on conventional B cells, constitutive activation of the AhR causes the loss of peritoneal B-l cells.65 B-l cells, also called CD5+B cells, represent a small subset of B lymphocytes that plays an important role in innate immune responses to viral and bacterial infections. Consequently, the observation that constitutive AhR activation results in depletion of this specialized lineage suggests that TCDD may affect innate immunity to pathogens via as yet uncharacterized affects on B-l cells. 

The expanding field of avian immunoecology has provided strong evidence that suppressed immunity leads to ecologically relevant consequences in wild birds. In a review of 12 immune function studies, immune responses were the most significant predictors of subsequent survival of young wild birds [107], In an assessment of 280 introduction attempts in 38 avian species, immunocompetence as assessed by the PHA skin response was an important positive predictor of the ability of birds to colonize new areas (i.e., found new local populations) [108], Similar assessments of survival, fitness, and dispersal ability should be conducted within the context of immunotoxicological studies of wild birds. 

Owing to the extreme sensitivity of certain susceptible individuals, an increasingly important concern among consumers is adverse reactions that occur as a consequence of food allergies or intolerances. Food allergies involve an abnormal immune response while food intolerances do not involve the immune system. 

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