Immune system diagram

Figure 6.15 Schematic diagram of a portion of the epithelium covering above a lymphatic nodule in a Peyer s patch (mouse). Attenuated M cells (M) extend as membranelike cytoplasmic bridges between the absorptive columnar epithelial cells present on either side (C). Beneath the M cell lies a small nest of intraepithelial lymphocytes (L) together with a central macrophage (Mac). The M cell provides a thin membrane-like barrier between the lumen above and the lymphocytes in the intercellular space below. This M cell has taken up the macromolecules and particulate matter that reach it and macrophages (Mac) may ingest them. Modified from D.H. Cormack. Lymphatic tissue and the immune system. D.H.Cormack (ed.) (1987) Ham s Histology, J.B. Lippincott Company, Philadelphia, pp. 234-263...

Figure 1.18. Alteruative Represeutatious of Proteiu Structure. A ribbon diagram (A) and a surface representation (B) of a key protein from the immune system emphasize different aspects of structure.

The EFAhas a differential effect on the production and the activity of ILs. For example, a diet based on n-3 PUFA abolishes the anorexia response to IL-1 (Endres, 1997, Calder, 1997, DePablo et al., 2000). DHA (n-3) administration causes a decrease in IL-1, IL-2, and TNF-a (Mohan and Das, 1997). The complex relationships between the endocrine and the immune system mediating stress is diagrammed in Fig. 1. 

A foreign bacterium enters the body. Describe with a diagram the possible immune system responses. 

Pourbaix has evaluated all possible equilibria between a metal M and HjO (see Table 1.7) and has consolidated the data into a single potential-pH diagram, which provides a pictorial summary of the anions and cations (nature and activity) and solid oxides (hydroxides, hydrated oxides and oxides) that are at equilibrium at any given pH and potential a similar approach has been adopted for certain M-H2O-X systems where A" is a non-metal, e.g. Cr, CN , CO, SOj , POj", etc. at a defined concentration. These diagrams give the activities of the metal cations and anions at any specified E and pH, and in order to define corrosion in terms of an equilibrium activity, Pourbaix has selected the arbitrary value of 10 ° g ion/1, i.e. corrosion of a metal is defined in terms of the pH and potential that give an equilibrium activity of metal cations or anions > 10 g ion/1 conversely, passivity and immunity are defined in terms of an equilibrium activity of < 10 g ion/1. (Note that g ion/1 is used here because this is the unit used by Pourbaix in the S.I, the relative activity is dimensionless.)... 

Although the zones of corrosion, immunity and passivity are clearly of fundamental importance in corrosion science it must be emphasised again that they have serious limitations in the solution of practical problems, and can lead to unfortunate misconceptions unless they are interpreted with caution. Nevertheless, Pourbaix and his co-workers, and others, have shown that these diagrams used in conjunction with E-i curves for the systems under consideration can provide diagrams that are of direct practical use to the corrosion engineer. It is therefore relevant to consider the advantages and limitations of the equilibrium potential-pH diagrams. 

Fig. 1.38(Equilibrium potential-pH diagram for the Cr-H20 system and (< ) potential-pH diagram showing zones of corrosion, passivity and immunity (after Pourbaix )... 

Over the years, Pourbaix and his co-workers in the CEBELCOR Institute, founded under his direction, extended these diagrams by including lines for metastable compounds. Figure 7.66 illustrates such a presentation for the Fe-O system over the temperature range 830-2200 K. Pourbaix used these diagrams as a basis for a discussion of the stability of metallic iron (solid, liquid and vapour phases), the oxides of iron as a function of oxygen pressure and temperature from which he explained the protection of iron at high temperature by immunity and passivation. He also pointed out the... 

The complexity of the systems to be protected and the variety of techniques available for cathodic protection are in direct contrast to the simplicity of the principles involved, and, at present the application of this method of corrosion control remains more of an art than a science. However, as shown by the potential-pH diagrams, the lowering of the potential of a metal into the region of immunity is one of the two fundamental methods of corrosion control. 

Before considering the principles of this method, it is useful to distinguish between anodic protection and cathodic protection (when the latter is produced by an external e.m.f.). Both these techniques, which may be used to reduce the corrosion of metals in contact with electrolytes, depend upon the electrochemical mechanisms that result from changing the potential of a metal. The appropriate potential-pH diagram for the Fe-H20 system (Section 1.4) indicates the magnitude and direction of the changes in the potential of iron immersed in water (pH about 7) necessary to make it either passive or immune in the former case the stability of the metal depends on the formation of a protective film of metal oxide (passivation), whereas in the latter the metal itself is thermodynamically stable and egress of metal ions from the lattice into the solution is thus prevented. 

Although important contributions in the use of electrical measurements in testing have been made by numerous workers it is appropriate here to refer to the work of Stern and his co-workerswho have developed the important concept of linear polarisation, which led to a rapid electrochemical method for determining corrosion rates, both in the laboratory and in plant. Pourbaix and his co-workers on the basis of a purely thermodynamic approach to corrosion constructed potential-pH diagrams for the majority of metal-HjO systems, and by means of a combined thermodynamic and kinetic approach developed a method of predicting the conditions under which a metal will (a) corrode uniformly, (b) pit, (c) passivate or (d) remain immune. Laboratory tests for crevice corrosion and pitting, in which electrochemical measurements are used, are discussed later. 

The whole-rock samples are not immune from other open-system exchange, however. For example, we do not yet know how aqueous alteration manifests itself on these diagrams because detailed studies of the Mg isotopic effects of water-rock reactions have not been carried out at the time of this writing. 

Herceptin attaches to the HER2/neu receptor and activates the complement system (a series of serum and cell-associated proteins involved in immune response) to destroy those cells expressing such receptors. Through this action, Herceptin disrupts the signaling pathway for breast cancer cell proliferation (refer to diagram below). 

Fig. 2.16 Pourbaix diagrams for the iron/water system, (a) Reproduction of Fig. 2.11 showing regions of corrosion, immunity, and possible passivation, (b) Form of the diagram frequently employed. Source Ref 9, 10...

The structure diagram of rockbolts quality diagnosis system based on immune danger theory is shown in Fig. 1. 

One frequently asked question concerning cathodic protection systems is what happens at the anode edge Is there a risk of accelerated corrosion This is a valid question and the risk is supported by the Pourbaix diagram which shows areas of imperfect passivity, pitting and corrosion around the immune and passive regions (Figure 7.2). However, the author knows of no atmospherically exposed reinforced concrete structure that is totally protected by cathodic protection. Most have anode zones that end before the reinforced concrete does. No cases of accelerated corrosion have been reported between zones or at the end of zones. 

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