Immune system, priming

Killed vaccines always require multiple doses. The first dose does not produce protective immunity. It primes the immune system, getting it ready to react. A protective immune response develops after the second or third dose. 

Although closely related, monocytes/macrophages (MO) possess features that are distinct from DCs. Due to their limited expression of T-cell costimulatory molecules, MO are not able to prime T cells de novo, but rather stimulate effector/memory T cells by the secretion of cytokines, which support T-cell proliferation. As DCs, MO differentiate from myeloid precursors and form a heterogeneous population of antigen-presenting cells (APCs) that link the innate and adaptive immune systems. However, their ability to interact with T cells via MHC class II TCR interaction(s) as well as engagement of T-cell costimulatory receptors on their surface, makes close contact between MO and Tregs likely to occur in vivo. 

Human milk is a s)mergistic package of essential nutrients and bioactive components. Epidemiological studies have demonstrated that consumption is associated with health benefits for many immune-related conditions (Table 2.1). Breast milk contains the nutrients necessary to support the development of the infant s immune system as well as other components that defend against infection. This includes various antimicrobial substances, factors that promote immime development, constituents that promote tolerance and the priming of the infant immime system, as well as anti-inflammatory components. The purpose of this chapter is to discuss the evidence for the immune benefits of human milk. 

In a more recent study, Webster et al. (2006) report the expression and characterization of lettuce-derived measles vaccine. The MV-H protein expressed in lettuce was demonstrated to be immunogenic in mice following intraperitoneal injection in the absence of adjuvant in addition to intranasal inoculation in the presence of a mucosal adjuvant. The highest response was observed in mice primed first with MV-H DNA and then boosted with an oral formulation of freeze-dried MV-H lettuce in conjunction with a mucosal adjuvant. In addition to this, the type of immune response was found to depend largely on the manner in which MV-H is presented to the immune system. Secreted and soluble forms of MV-H were demonstrated to induce a Th2 type response, while membrane-bound MV-H protein was found to be associated with a Thl response. 

Active immunity occurs when the organism is exposed to a toxin or infectious agent (bacterium, virus, or parasite) so that the immune system is stimulated. Most of your parents, grandparents, and instructors contracted measles, mumps and chicken pox when they were children and so are now naturally immune to such agents because their antigenic memory (B and T cells) is primed for a full scale IgG response. 

Lipopolysaccharides are the dominant surface feature of the outer membrane of gram-negative bacteria such as Escherichia coli and Salmonella ty-phimurium. These molecules are prime targets of the antibodies produced by the vertebrate immune system in response to bacterial infection and are therefore important determinants of the serotype of bacterial strains (serotypes are strains that are distinguished on the basis of antigenic properties). The lipopolysaccharides of S. typhimurium contain six fatty acids bound to two... 

Proteins derived from viral coats are as effective in priming an immune system as is the killed virus more traditionally used for vaccines, and are safer first developed was the vaccine for hepatitis B. 

Nevertheless, there is also accumulating evidence that a certain regionalization exists in the mucosal immune system, in particular a dichotomy between the gut and the upper respiratory tract. Differences in the antigenic repertoire, adhesion molecules or chemokines involved in leukocyte extravasation might explain this disparity. Primed immune cells may tend to home to the effector sites corresponding to the inductive sites, where the initial antigen contact took place. Such regionalization within the common mucosal immune system has to be taken into account in the development of certain mucosal vaccines [11]. 

Leishman AJ, Garside P, Mowat AM Induction of oral tolerance in the primed immune system Influence of antigen persistence and adjuvant form. Cell Immunol 2000 202 71-78. 

The future importance of peptide vaccines lies in the fact that one could replace inactivated or attenuated microbial pathogens or toxins, which are high-molecular and therefore difficult to characterize and standardize, by highly specific synthetic peptides. Emini et al.157 have synthesized oligopeptides that prime the rabbit immune system and are effective against poliovirus. The amino acid sequence of the peptide vaccines 63 and 64 originate in the poliovirus VPt protein. 

The relationship being found between endocrine system, the nervous system, and immune system will make these endpoints prime areas for further development of chronic toxicity test methods for aquatic organisms and should be considered for ecological and hazard risk assessments of chemicals [7,386]. 

As stated above, the principal objective for the use of an adjuvant in a vaccine is to potentiate immune response to an Ag of minimal immunogenicity. How this potentiation is achieved varies from adjuvant to adjuvant and in many cases, the precise mechanism of ac tion is unknov n. However, as a rule, immune potentiation is accomplished by the ability of the adjuvant to induce a variety of non-specific activities within the innate arm of the immune system. Once activated, the innate branch of immunity, particularly the complement system, orchestrates the various humoral and cell-mediated responses that operate within and between the innate and acquired arms. The result is a generalized activation and potentiation of the immune system in response to the adjuvant with the hope that this generalized immune priming will allow for a more effective processing and recognition of the Ag contained within the vaccine. 

Crouch CE, Daly J, Henly W, Hannant D, Wilkins J, Erancis Ml (2005) The use of a systemic prime/mucosal boost strategy with an equine influenza ISCOM vaccine to induce protective immunity in horses. Vet Immunol Immunopathol 108 345-355. 

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