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The genome organisation of HBV; the genes overlap. ORF S, in green, encodes HBsAg. HBsAg under a transmission electron microscope: the protein self assembles into virus-like particles. HBsAg (also known as the Australia antigen) is the surface antigen of the hepatitis B virus (HBV). Its presence in blood indicates existing hepatitis B infection.
HBeAg is an antigen that can be found between the icosahedral nucleocapsid core and the lipid envelope (the outer most layer of the hepatitis b virus).However, HBeAg is considered "nonparticulate" or "secretory". [2]
Blood compatibility testing is routinely performed before a blood transfusion.The full compatibility testing process involves ABO and RhD (Rh factor) typing; screening for antibodies against other blood group systems; and crossmatching, which involves testing the recipient's blood plasma against the donor's red blood cells as a final check for incompatibility.
The time between the removal of the HBsAg and the appearance of anti-HBs is called the window period. A person negative for HBsAg but positive for anti-HBs either has cleared an infection or has been vaccinated previously. Individuals who remain HBsAg positive for at least six months are considered to be hepatitis B carriers. [68]
If HBsAg is present, a second test – usually done on the same blood sample – that detects the antibody for the hepatitis B core antigen (anti-HBcAg) can differentiate between acute and chronic infection. [85] [89] People who are high-risk whose blood tests negative for HBsAg can receive the hepatitis B vaccine to prevent future infection.
In immunology, the definition of cross-reactivity refers specifically to the reaction of the immune system to antigens. There can be cross-reactivity between the immune system and the antigens of two different pathogens, or between one pathogen and proteins on non-pathogens, which in some cases can be the cause of allergies.
The half-life of HBIG is about 3 weeks. In lieu of a booster administration of HBIG, a hepatitis B vaccination is initiated at the time of the initial HBIG administration, thus providing long term protection. [9] HBIG is classified as pregnancy category C substance by the U.S. Food and Drug Administration. [citation needed]
Reference ranges (reference intervals) for blood tests are sets of values used by a health professional to interpret a set of medical test results from blood samples. Reference ranges for blood tests are studied within the field of clinical chemistry (also known as "clinical biochemistry", "chemical pathology" or "pure blood chemistry"), the ...