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The Chemic Messengers Of The Immune System

Immunoglubulins(antibodies)

The chemic data of immunoglobulin was provided past times Tiselius in addition to Kabat inwards the early on 1940s. In 1950s, Porter in addition to Edelman revealed the basic construction of immunoglobulin molecule. Antibodies are products of antigen- activated B- lymphocytes. They are the primary effectors of humoral immunity. They bind antigens amongst high specificity in addition to affinity.

Structure of Immunoglobulins

This glycoprotein is Y-shaped molecules in addition to has 2 identical binding sites for its antigen, i on either arm of the Y. This poly peptide is composed of 4 polypeptide chains (two identical heavy chains in addition to 2 identical in addition to smaller calorie-free chains) held together past times disulfide bonds. The antibody molecule has 2 identical calorie-free chains (L chains), each containing nearly 200 amino acids in addition to 2 identical heavy chains (H chains), each made upwards of 400 amino acids. Each chain is made upwards of several dissimilar domains. The antigen-binding site is formed where a heavy chain variable domain (VH) in addition to a calorie-free chain variable domain (VL) come upwards closed together. These are the domains that differ most inwards their sequence in addition to construction inwards dissimilar antibodies.
The variable (V) regions
The get-go 100 or in addition to thence amino acids at the N-terminal of both H in addition to L chains vary greatly from antibody to antibody. These are the variable (V) regions. The amino acid sequence variability inwards the V regions is specially pronounced inwards 3 hypervariable regions. Together they build the antigen binding site against which the epitope fits. Only a few dissimilar amino acid sequences are flora inwards the C-terminals of H in addition to L chains. These are the constant (C) regions.
The constant (C) regions
The 2 dissimilar kinds of C regions for their L chains producing kappa (κ) L chains in addition to lambda (λ) L chains. There are v dissimilar kinds of C regions for their H chains producing mu (µ) chains (the H chain of IgM antibodies), gamma (γ) chains (IgG), alpha (α) chains (IgA), delta (δ) chains (IgD) in addition to epsilon (ε) chains (IgE).

Fc in addition to Fab regions

The proteolytic enzyme papain breaks each Ig molecule into 3 fragments at the hinge region. The unmarried crystallizable fragment (Fc region) includes component of the constant domain that occupies the stem. There are 2 antigen-binding fragments (Fab region), which include the entire calorie-free chain in addition to variable in addition to constant portions of the heavy chain.

Subclasses of human immunoglobulins

There are nine chemically distinct classes of human immunoglobulins, 4 kinds of IgG in addition to 2 kinds of IgA, summation IgM, IgE, in addition to IgD. Immunoglobulins G, D, in addition to E are similar inwards appearance.
The classes of human immunoglobulins are  based on construction in addition to function.
·         IgM -secreted during primary reply
·         IgG -secreted during secondary reply
·         IgD -receptors for antigens on B cells
·         IgA -found inwards external secretions
·         IgF -promotes histamine release
Defense mechanisms of antibodies
 1.Opsonization
2. MAC cytolysis
3. Antibody-dependent cellular cytotoxicity (ADCC) past times NK Cells
4. Neutralization of exotoxins
5. Neutralization of viruses
6. Preventing bacterial adherence to host cells
7. Agglutination of microorganisms
8. Immobilization of bacteria in addition to protozoans.

Cytokines

They are non- antibody proteins produced past times cells of the immune organisation (including T cells, B cells, monocytes, in addition to macrophages). Cytokines include a various grouping of interleukins, interferons, in addition to growth factors. Cytokines are chemic switches that plough for sure immune jail cellphone types on in addition to off. One cytokine, interleukin 2 (IL-2), triggers the immune organisation to create T cells. Cytokines likewise are existence studied for their potential clinical benefit.


Kinds of cytokines
1. Monokines - produced past times mononuclear phagocytes
2. Lymphokines - produced past times activated T cells, primarily helper T cells
3. Interleukins - elevate given to many cytokines, abbreviated equally IL in addition to given a     number
Functions of cytokines
·         Activation of the Immune cells
·         Promotion of jail cellphone growth, pregnant maturation, and/or sectionalisation
·         Attraction of cells to the site of infection
·         Destruction infected or malignant cells
·         Stimulation of phagocytic activity.

Chemokines

The elevate chemokine is a contraction of chemotactic cytokines. These are a large household unit of measurement of substances (more than 50) produced past times many dissimilar leukocytes in addition to tissue cells. They recruit leukocytes to sites of infection. They play a role inwards lymphocyte trafficking.
Properties of chemokines
Chemokines are produced past times cells involved inwards both natural in addition to specific immunity. They mediate in addition to regulate immune in addition to inflammatory responses. The secretion is brief in addition to limited. Many private cytokines are produced past times many jail cellphone types in addition to human activity on many jail cellphone types (they are pleiotropic). In many cases cytokines bring similar actions (they are redundant).
Tumor Necrosis Factor, TNF-gamma
It is produced past times activated macrophages. It is the most of import mediator of astute inflammation inwards reply to Gram-negative bacteria in addition to other infectious microbes. It mediates the recruitment of polymorphonuclear leukocytes (PMNs) in addition to monocytes to the site of infection: acts on the hypothalamus to create fever in addition to promotes the production of astute stage proteins past times the liver.
Interleukin-2
It is produced mainly past times helper T cells (CD4+); less past times cytoxic T cells (CD8+). It promotes T jail cellphone sectionalisation in addition to increases production of other cytokines. It has autocrine functions on T jail cellphone proliferation.
Interleukin-4
It is produced mainly past times Th2 subpopulation of helper T cells (CD4+). It stimulates immunoglobulin flat switching to the IgE isotype in addition to evolution of Th2 cells from naive CD4+ T cells. It likewise promotes growth of differentiated Th2 cells.
Interleukin-5
It is produced mainly past times the Th2 subpopulation of helper T cells (CD4+). It promotes growth in addition to differentiation of eosinophils in addition to activates mature eosinophils.
Interferons (IFN)
There are iii groups of interferons: IFN-alpha , IFN-beta , IFN-gamma. Twenty variants of IFN-alpha are produced past times leukocytes inwards reply to viruses. IFN-beta is a unmarried poly peptide produced past times fibroblasts in addition to other cells inwards reply to viruses. Both IFN-alpha in addition to IFN-beta inhibit viral replication in addition to increment seem of flat I MHC on cells. IFN-gamma is produced past times the Th1 subpopulation of helper T cells (CD4+), cytotoxic T cells (CD8+), in addition to NK cells. IFN-gamma functions inwards both natural in addition to specific immunity.
Transforming Growth Factor (TGF-beta)
It is an inhibitory cytokine produced past times T cells, macrophages, in addition to many other jail cellphone types. It inhibits proliferation in addition to differentiation of T cells. It inhibits activation of macrophages. It acts on PMN in addition to endothelial cells to block the effects of pro-inflammatory cytokines.

The complement system

The complement organisation consists of to a greater extent than than 35 soluble in addition to cell-bound proteins ,12 of which are demand involved inwards the complement pathways. The proteins trouble concern human relationship for 5% of the serum globulin fraction . Most of these proteins circulate equally zymogens , which are inactive until proteolytic cleavage . The complement proteins are synthesized mainly past times hepatocytes ; however, important amounts are likewise produced past times Monocytes, macrophages, in addition to epithelial cells inwards the gastrointestinal in addition to Genitourinary tracts.

Secretory molecules of non-specific immunity

These include organic acids inwards peel secretions, thiocyanate inwards saliva, depression molecular weight obese acids inwards the lower bowel; bile acids in addition to depression molecular weight obese acids inwards lower GI tract; transferrin, lactoferrin, lysozyme, interferons, fibronectin, complement, astute stage proteins, etc. inwards serum; Interferons in addition to tumor necrosis gene (TNF) at the site of inflammation. Transferrin in addition to lactoferrin deprive organisms of iron. Interferon inhibits viral replication in addition to activates other cells which kill pathogens. Lysozyme, inwards serum in addition to tears, breaks downward the bacterial jail cellphone wall (peptidoglycan). Fibronectin coats (opsonizes) bacteria in addition to promotes their rapid phagocytosis. Complement components in addition to their products motion devastation of microorganism demand or amongst the assist of phagocytic cells. Acute stage proteins (such equally CRP) interact amongst the complement organisation proteins to scrap infections. TNF-alpha suppresses viral replication in addition to activates phagocytes.



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