Somatic Fusion

Somatic fusion, also called protoplast fusion, is a type of genetic modification in plants by which two distinct species of plants are fused together to form a new hybrid plant with the characteristics of both, a somatic hybrid. Hybrids have been produced either between the different varieties of the same species (e.g. between non-flowering potato plants and flowering potato plants) or between two different species (e.g. between wheat triticum and rye secale to produce Triticale).

Uses of somatic fusion include making potato plants resistant to potato leaf roll disease. Through somatic fusion, the crop potato plant Solanum tuberosum – the yield of which is severely reduced by a viral disease transmitted on by the aphid vector – is fused with the wild, non-tuber-bearing potato Solanum brevidens, which is resistant to the disease. The resulting hybrid has the chromosomes of both plants and is thus similar to polyploid plants.

Immunoglobulin IgM

Immunoglobulin M, or IgM for short, is a basic antibody that is produced by B cells. It is the primary antibody against A and B antigens on red blood cells. IgM is by far the physically largest antibody in the human circulatory system. It is the first antibody to appear in response to initial exposure to antigen.

Structure and function

IgM forms polymers where multiple immunoglobulins are covalently linked together with disulfide bonds, mostly as a pentamer but also as a hexamer. IgM has a molecular mass of approximately 900 kDa (in its pentamer form). Because each monomer has two antigen binding sites, a pentameric IgM has 10 binding sites. Typically, however, IgM cannot bind 10 antigens at the same time because the large size of most antigens hinders binding to nearby sites.

The J chain is found in pentameric IgM but not in the hexameric form, perhaps due to space constraints in the hexameric complex. Pentameric IgM can also be made in the absence of J chain. At present, it is still uncertain what fraction of normal pentamer contains J chain, and to this extent it is also uncertain whether a J chain-containing pentamer contains one or more than one J chain.

Because IgM is a large molecule, it cannot diffuse well, and is found in the interstitium only in very low quantities. IgM is primarily found in serum; however, because of the J chain, it is also important as a secretory immunoglobulin.

Due to its polymeric nature, IgM possesses high avidity, and is particularly effective at complement activation. By itself, IgM is an ineffective opsonin; however it contributes greatly to opsonization by activating complement and causing C3b to bind to the antigen

 

Transposons

Transposons are sequences of DNA that can move or transpose themselves to new positions within the genome of a single cell. The mechanism of transposition can be either "copy and paste" or "cut and paste". Transposition can create phenotypically significant mutations and alter the cell's genome size.
Transposons make up a large fraction of the C-value of eukaryotic cells. Transposons are often considered "junk DNA". In Oxytricha, which has a unique genetic system, they play a critical role in its development. Transposons are very useful to researchers as a means to alter DNA inside a living organism.

Happy Diwali

May this Diwali fills ur life with colors of rangoli, lights of diya and sweetness of sweets.

"HAPPY DEEPAWALI TO ALL"

Secondary metabolites

Secondary metabolites are organic compounds that are not directly involved in the normal growth, development, or reproduction of an organism. Unlike primary metabolites, absence of secondary metabolities does not result in immediate death, but rather in long-term impairment of the organism's survivability, fecundity, or aesthetics, or perhaps in no significant change at all. Secondary metabolites are often restricted to a narrow set of species within a phylogenetic group. Secondary metabolites often play an important role in plant defense against herbivory and other interspecies defenses. Humans use secondary metabolites as medicines, flavorings, and recreational drugs.

Mitogens

A mitogen is a chemical substance that encourages a cell to commence cell division, triggering mitosis. A mitogen is usually some form of a protein. Mitogenesis is the induction (triggering) of mitosis, typically via a mitogen. Mitogens trigger signal transduction pathways in which mitogen-activated protein kinase is involved, leading to mitosis.

Use in immunology

B cells can enter mitosis when they encounter an antigen matching their immunoglobulin. Mitogens are often used to stimulate lymphocytes and therefore assess immune function. The most commonly used mitogens in clinical laboratory medicine are:

Name	Acts upon T cells?	Acts upon B cells?
phytohaemagglutinin (PHA)	yes	no
concanavalin A (conA)	yes	no
lipopolysaccharide (LPS)	no	yes
pokeweed mitogen (PWM)	yes	yes

Lipopolysaccharide toxin from gram-negative bacteria is thymus-independent. They may directly activate B cells, regardless of their antigenic specificity. Plasma cells are terminally differentiated and, therefore, cannot undergo mitosis. Memory B cells can proliferate to produce more memory cells or plasma B cells. This is how the mitogen works, that is, by inducing mitosis in memory B cells to cause them to divide, with some becoming plasma cells.

Mitogens in human physiology

Insulin-like Growth Factor 1 mediates the major growth-promoting effect of Human Growth Hormone as a paracrine agent at growth plates in the skeletal system.

Adjuvants

An adjuvant (from Latin, adiuvare: to aid) is a pharmacological or immunological agent that modifies the effect of other agents, such as a drug or vaccine, while having few if any direct effects when given by itself. They are often included in vaccines to enhance the recipient's immune response to a supplied antigen, while keeping the injected foreign material to a minimum.

Immunologic adjuvants

Immunologic adjuvants are added to vaccines to stimulate the immune system's response to the target antigen, but do not in themselves confer immunity. Adjuvants can act in various ways in presenting an antigen to the immune system. Adjuvants can act as a depot for the antigen, presenting the antigen over a long period of time, thus maximizing the immune response before the body clears the antigen. Examples of depot type adjuvants are oil emulsions. Adjuvants can also act as an irritant which causes the body to recruit and amplify its immune response. A tetanus, diphtheria, and pertussis vaccine, for example, contains minute quantities of toxins produced by each of the target bacteria, but also contains some aluminum hydroxide. Such aluminum salts are common adjuvants in vaccines sold in the United States and have been used in vaccines for over 70 years. The body's immune system develops an antitoxin to the bacteria's toxins, not to the aluminum, but would not respond enough without the help of the aluminum adjuvant.

Adjuvants as stabilizing agents

Although immunological adjuvants have traditionally been viewed as substances that aid the immune response to antigen, adjuvants have also evolved as substances that can aid in stabilizing formulations of antigens, especially for vaccines administered for animal health.

Cause of AIDS

AIDS is the ultimate clinical consequence of infection with HIV. HIV is a retrovirus that primarily infects vital organs of the human immune system such asCD4⁺ T cells (a subset of T cells), macrophages and dendritic cells. It directly and indirectly destroys CD4⁺ T cells.

Once the number of CD4⁺ T cells per microliter (µL) of blood drops below 200, cellular immunity is lost. Acute HIV infection usually progresses over time to clinical latent HIV infection and then to early symptomatic HIV infection and later to AIDS, which is identified either on the basis of the amount of CD4⁺ T cells remaining in the blood, and/or the presence of certain infections, as noted above.

In the absence of antiretroviral therapy, the median time of progression from HIV infection to AIDS is nine to ten years, and the median survival time after developing AIDS is only 9.2 months. However, the rate of clinical disease progression varies widely between individuals, from two weeks up to 20 years.

Many factors affect the rate of progression. These include factors that influence the body's ability to defend against HIV such as the infected person's general immune function. Older people have weaker immune systems, and therefore have a greater risk of rapid disease progression than younger people.

Poor access to health care and the existence of coexisting infections such as tuberculosis also may predispose people to faster disease progression. The infected person's genetic inheritance plays an important role and some people are resistant to certain strains of HIV. An example of this is people with the homozygous CCR5-Δ32 variation are resistant to infection with certain strains of HIV. HIV is genetically variable and exists as different strains, which cause different rates of clinical disease progression.

There are a number HIV and AIDS misconceptions. Three of the most common are that AIDS can spread through casual contact, that sexual intercourse with a virgin will cure AIDS, and that HIV can infect only homosexual men and drug users. Other misconceptions are that any act of anal intercourse between gay men can lead to AIDS infection, and that open discussion of homosexuality and HIV in schools will lead to increased rates of homosexuality and AIDS.

Active and Passive immunity

Active immunity is a form of immunity that develops after a primary immune response which is a response to exposure to a live pathogen and development of symptoms. The cells produce the antibodies themselves.

Passive immunity is a form of immunity in which a person's cells do not produce the antibodies, they receive them by an injection of antibodies or antitoxin.

Mucosa-associated lymphoid tissue

The mucosa-associated lymphoid tissue (MALT) (also called mucosa-associated lymphatic tissue) is the diffusion system of small concentrations of lymphoid tissue found in various sites of the body, such as the gastrointestinal tract, thyroid, breast, lung, salivary glands, eye, and skin.

MALT is populated by lymphocytes such as T cells and B cells, as well as plasma cells and macrophages, each of which is well situated to encounter antigens passing through the mucosal epithelium. In the case of intestinal MALT, M cells are also present, which sample antigen from the lumen and deliver it to the lymphoid tissue.

Components

The components of MALT are sometimes subdivided into the following:

• GALT (gut-associated lymphoid tissue. Peyer's patches are a component of GALT found in the lining of the small intestines.)
• BALT (bronchus-associated lymphoid tissue)
• NALT (nose-associated lymphoid tissue)
• LALT (larynx-associated lymphoid tissue)
• SALT (skin-associated lymphoid tissue)
• VALT (vascular-associated lymphoid tissue. A newly recognized entity that exists inside arteries; its role in the immune response is unknown.)
• EALT (eye-associated lymphoid tissue made up of Conjunctiva [CALT] and Lacrimal Duct [LDALT] associated lymphoid tissues)

Role in disease

MALT plays a role in regulating mucosal immunity. It may be the site of lymphoma, usually non-Hodgkin lymphoma. A specific entity is the MALT lymphoma linked to Helicobacter pylori in the stomach.

Hematopoiesis

Difference between disinfection & sterlization

Disinfection simply means that you are reducing the microbial load on an object. Since this is usually done to render the object less likely to be involved in the transmission of infection, a good disinfection procedure is aimed at specifically reducing the numbers of potentially pathogenic organisms in the context of the use of the object being disinfected.

An object that has been disinfected is less likely to transmit infection that one that hasn't but because there is only a reduction in the number of microorganisms, their is no guarantee.

Sterilisation is absolute. It means that ALL of the microorganisms have either been removed or killed. A sterile object has NO viable microbial cells present.

Antibody dependent cell mediated cytotoxicity

Antibody-Dependent Cell-Mediated Cytotoxicity (ADCC) is a mechanism of cell-mediated immunity whereby an effector cell of the immune system actively lyses a target cell that has been bound by specific antibodies. It is one of the mechanisms through which antibodies, as part of the humoral immune response, can act to limit and contain infection. Classical ADCC is mediated by natural killer (NK) cells; neutrophils and eosinophils can also mediate ADCC. For example, eosinophils can kill certain parasitic worms known as helminths through ADCC. ADCC is part of the adaptive immune response due to its dependence on a prior antibody response.

ADCC by NK cells

The typical ADCC involves activation of NK cells by antibodies. An NK cell's Fc receptor recognizes the Fc portion of an antibody, such as IgG, which has bound to the surface of a pathogen-infected target cell. The most common Fc receptor on the surface of an NK Cell is called CD16 or FcγRIII. Once the Fc receptor binds to the Fc region of IgG, the Natural Killer cell releases cytokines such asIFN-γ, and cytotoxic granules containing perforin and granzymes that enter the target cell and promote cell death by triggering apoptosis. This is similar to, but independent of, responses by cytotoxic T cells (CTLs).

ADCC by eosinophils

Large parasites like helminths are too big to be engulfed and killed by phagocytosis. They also have an external structure or integument that is resistant to attack by substances released by neutrophilsand macrophages. However, an antibody called IgE can coat these parasites. The Fc receptor (FceRI) of an eosinophil can then recognize IgE. The interaction between FceRI and the Fc portion of helminth-bound IgE causes the eosinophil to degranulate.

Antibody-dependent cellular cytotoxicity