42.3 Antibodies

42.3 Antibodies

• The spleen is larger than a lysy and filters blood instead of lysy.
• The red pulp stores blood.
• Red blood cells are removed and replaced with new ones.
• The white pulp is rich in immune cells.

• Antibodies are the basis of humoral immunity.
• Antibodies can be found in the blood, mucus and breast milk.
• Antibodies in bodily fluids can destroy pathogens before they get to cells.

• Two heavy chains and two small light chains are bound to each other in a "Y" formation, as shown in.
• The polypeptides are attached to each other by bonds between the cysteine amino acids.
• The areas where the antigen is recognized are variable and the base is composed of constant domains.

• The variable region of the light chain genes in germ-line B cells has 40 and five segments.
• Most of these segments are excised and one V segment is replaced with one J segment by the DNA recombinase.

• All but one of the V and J segments are cut out.
• Recombination and splicing can result in over 100 possible combinations.
• Each differentiated B cell in the human body has a unique variable chain.
• The constant domain is the same for all antibodies.

• Further gene rearrangement occurs when the levels of the mRNA are manipulated.
• Each antibody has a variable region that can bind a different antigen.

• Similar to BCRs and TCRs, antibody diversity is produced by themutation and recombination of hundreds of different genes in cells that are destined to become B cells.
• The binding site is formed by the variable domains from the heavy and light chains.
• The numbers of repeated constant domains in Ig classes are the same for all antibodies.
• Antibodies are similar to the BCRs in structure and can be visualized in simple terms as the cell acquires the ability to produce large quantities of BCR.

• Antibodies can be divided into five classes based on their properties.
• About 80 percent of all antibodies have heavy chains that consist of one variable domain and three identical constant domains.
• IgA, IgD, and IgM all have three constant domains per heavy chain.
• The binding specificity is determined by the variable domain and the immunological mechanism of action is determined by the heavy chain.

• After an adaptive defense is produced against a pathogen, the blood contains IgM.
• BCRs on naive B cells are part of the IgM and IgD classes.
• Ten percent of all antibodies are IgM molecules.
• These macromolecules are able to bind ten different antigens thanks to the pentamer arrangement.

• IgM molecules released early in the adaptive immune response do not bind to antigens as stably as IgGs, which are one of the possible types of antibodies that can be produced in large quantities upon reexposure to the same pathogen.

• Light and heavy chains form a Y-shaped structure in immunoglobulins, which have different functions.

• IgAs are present in saliva, tears, breast milk, and mucus.

• The bodily fluids coat and protect the entire body.
• The number of IgA molecule in bodily fluids is greater than the number of IgA molecule in the blood.
• There is a small amount of IgA in the serum.
• Some IgM is released into bodily fluids.
• IgA molecule are linked with a J chain and are similar to IgM.
• IgAs are mostly dimeric molecules.

• In small quantities, IgE is present in the serum and is an allergy mediator.
• In small quantities, IgD is present.
• Similar to IgM, BCRs of the IgD class are found on naive B cells.
• The class supports the recognition and maturation of B cells.

• Differentiated plasma cells are important players in the humoral response, and are particularly important against toxins.
• Antibodies act independently of the cells.

• Antibodies can be transferred from one person to another.
• A person who has recently produced a successful immune response against a disease can donate blood to a nonimmune recipient and give them temporary immunity through the donor's blood serum.

• It is possible to prevent pathogens from entering and infecting host cells, as opposed to the CTL-mediated approach of killing cells that are alreadyinfecting to prevent progression of an established infection.
• The neutralizing antibodies can be used to eliminate the pathogens in urine or feces.

• Antibodies may prevent the antigen from binding its target, tag a pathogen for destruction by macrophages or neutrophils, or cause the complement cascade to cascade.

• Antibodies mark pathogens for destruction by phagocytic cells because they are attracted to macromolecules.
• Opsonization is the enhancement of phagocytic cells.
• The process of complement fixation involves IgM and IgG in the blood providing docking sites for complement proteins.
• The combination of antibodies and complement increases opsonization.

• The strength of binding is not the only measure of avidity.
• The avidity is dependent on a number of physical and chemical factors.
• Multimeric IgM, for example, is classified as having a lower affinity than a monomeric one.
• The fact that multimeric antibodies can bind many different antigens at the same time balances their lower binding strength for each interaction.

• cross reactivity for the same or similar epitopes on different antigens is a possibility.
• It is possible for different macromolecules to have the same identities and orientations over short regions, because an epitope corresponds to a small region.

• If an individual develops immunity to several related pathogens despite only being exposed to one of them, cross reactivity can be beneficial.
• The surface structures of various Gram-negativebacteria may have similar antibody cross reactivity.
• Host cells may be mistakenly marked for destruction by the antibodies raised against them.
• Patients who develop SLE often have their own antibodies that react with their own genes.
• The antibodies may have been raised against the nucleic acid of the microorganisms.
• This phenomenon is called mimicry.