Antigenic variation refers to the observation that different isolates of a single virus species may show variable cross-reactivity when tested with a standard serum.

What is meant by antigenic variation?

Antigenic variation refers to the observation that different isolates of a single virus species may show variable cross-reactivity when tested with a standard serum.

What does antigenic variation do? Antigenic variation makes the pathogen evade detection of the immune cells by altering their surface antigens. This gives the pathogen the advantage of repeatedly infecting the same host (re-infection) and therefore prolongs its stay within the host. It also increases the chance of being transmitted to a new host.

How does antigenic variation affect vaccines?

Selection pressures of the host’s immune response can drive antigenic variability of surface molecules. Antigenic variants of many pathogens are problematic for vaccine design and remain a major reason for the inability to control some infectious diseases.

What is antigenic variation BBC Bitesize?

However some pathogens have the ability to alter their antigens. As a result, memory cells do not detect the altered antigens and are no longer effective against the pathogen. This is called antigenic variation.

Is antigenic variation reversible?

Alternating between two phenotypes in a heritable and reversible manner can be classified as phase variation or antigenic variation.

What are mechanisms of antigenic variation?

Antigenic variation in microbes is created via two general types of mechanisms, genetic and epigenetic. Genetic events (mutation and recombination) change the DNA sequence of an antigen encoding gene or its regulatory elements, thereby altering either the level of expression or the amino acid sequence of its product.

What is the difference between antigenic and phase variation?

Phase variation or phenotypic switch allows the expression of a given phenotype to be switched ON or OFF. Antigenic variation refers to the expression of a number of alternative forms of an antigen on the cell surface, and at a molecular level, shares common features with phase variation mechanisms.

What triggers humoral immunity?

The humoral immune response is mediated by antibody molecules that are secreted by plasma cells. Antigen that binds to the B-cell antigen receptor signals B cells and is, at the same time, internalized and processed into peptides that activate armed helper (more…)

What is the difference between immunogen and antigen?

An immunogen refers to a molecule that is capable of eliciting an immune response by an organism’s immune system, whereas an antigen refers to a molecule that is capable of binding to the product of that immune response. So, an immunogen is necessarily an antigen, but an antigen may not necessarily be an immunogen.

What is bacterial phase variation?

Phase variation is the adaptive process by which bacteria undergo frequent and reversible phenotypic changes resulting from genetic alterations in specific loci of their genomes. This process is crucial for the survival of pathogens and commensals in hostile and ever-changing host environments.

What is antigenic variation in trypanosomes?

Antigenic variation in African trypanosomes. … Trypanosome persistence in the mammal is due to antigenic variation, which involves changes in the identity of the variant surface glycoprotein (VSG) that forms a dense cell surface coat to shield invariant surface antigens from immune recognition.

What causes antigenic drift to occur in viral infections?

Antigenic drift is a kind of genetic variation in viruses, arising from the accumulation of mutations in the virus genes that code for virus-surface proteins that host antibodies recognize.

What are the 2 main types of lymphocytes?

Lymphocytes are cells that circulate in your blood that are part of the immune system. There are two main types lymphocytes: T cells and B cells. B cells produce antibody molecules that can latch on and destroy invading viruses or bacteria.

What is in an antigen?

In general, antigens are composed of proteins, peptides, and polysaccharides. Any portion of bacteria or viruses, such as surface protein, coat, capsule, toxins, and cell wall, can serve as antigens.

Do all antibodies respond to any antigen?

Antibody responses are typically polyclonal, meaning that many clones of B cells are stimulated, and the array of antibodies produced recognizes many different epitopes.