Seroconversion
Encyclopedia
Seroconversion is the development of detectable specific antibodies to microorganism
s in the blood serum
as a result of infection
or immunization
. Serology
(the testing for antibodies) is used to determine antibody positivity. Prior to seroconversion, the blood test is seronegative for the antibody
; after seroconversion, the blood test is seropositive for the antibody.
The word is often used in reference to blood testing for anti-HIV
antibodies. In particular, "seroconverted" has been used to refer to the process of having "become HIV positive."
Seroreversion is the opposite of seroconversion. This is when the tests can no longer detect antibodies
in a patient’s serum.
maintains an "immunological memory" against past pathogens to facilitate early detection and to confer protective immunity against a rechallenge
. This explains why many childhood diseases never recur in adulthood (and when they do, it generally indicates immunosuppression
or failure of a vaccine).
In the initial (primary infection) phase of the infection, immunoglobulin M
(IgM) antibodies are produced and as these levels drop (and become undetectable) immunoglobulin G
(IgG) levels rise and remain detectable. Upon reinfection, IgM antibodies usually do not rise again but IgG levels will increase. Thus an elevated IgM titre indicates recent primary infection, while the presence of IgG suggests past infection or immunization
.
Microorganism
A microorganism or microbe is a microscopic organism that comprises either a single cell , cell clusters, or no cell at all...
s in the blood serum
Blood plasma
Blood plasma is the straw-colored liquid component of blood in which the blood cells in whole blood are normally suspended. It makes up about 55% of the total blood volume. It is the intravascular fluid part of extracellular fluid...
as a result of infection
Infection
An infection is the colonization of a host organism by parasite species. Infecting parasites seek to use the host's resources to reproduce, often resulting in disease...
or immunization
Immunization
Immunization, or immunisation, is the process by which an individual's immune system becomes fortified against an agent ....
. Serology
Serology
Serology is the scientific study of blood serum and other bodily fluids. In practice, the term usually refers to the diagnostic identification of antibodies in the serum...
(the testing for antibodies) is used to determine antibody positivity. Prior to seroconversion, the blood test is seronegative for the antibody
Antibody
An antibody, also known as an immunoglobulin, is a large Y-shaped protein used by the immune system to identify and neutralize foreign objects such as bacteria and viruses. The antibody recognizes a unique part of the foreign target, termed an antigen...
; after seroconversion, the blood test is seropositive for the antibody.
The word is often used in reference to blood testing for anti-HIV
HIV
Human immunodeficiency virus is a lentivirus that causes acquired immunodeficiency syndrome , a condition in humans in which progressive failure of the immune system allows life-threatening opportunistic infections and cancers to thrive...
antibodies. In particular, "seroconverted" has been used to refer to the process of having "become HIV positive."
Seroreversion is the opposite of seroconversion. This is when the tests can no longer detect antibodies
Antibody
An antibody, also known as an immunoglobulin, is a large Y-shaped protein used by the immune system to identify and neutralize foreign objects such as bacteria and viruses. The antibody recognizes a unique part of the foreign target, termed an antigen...
in a patient’s serum.
Background
The immune systemImmune system
An immune system is a system of biological structures and processes within an organism that protects against disease by identifying and killing pathogens and tumor cells. It detects a wide variety of agents, from viruses to parasitic worms, and needs to distinguish them from the organism's own...
maintains an "immunological memory" against past pathogens to facilitate early detection and to confer protective immunity against a rechallenge
Challenge-dechallenge-rechallenge
Challenge-dechallenge-rechallenge is a medical testing protocol in which a medicine or drug is administered, withdrawn, then re-administered, while being monitored for adverse effects at each stage...
. This explains why many childhood diseases never recur in adulthood (and when they do, it generally indicates immunosuppression
Immunosuppression
Immunosuppression involves an act that reduces the activation or efficacy of the immune system. Some portions of the immune system itself have immuno-suppressive effects on other parts of the immune system, and immunosuppression may occur as an adverse reaction to treatment of other...
or failure of a vaccine).
In the initial (primary infection) phase of the infection, immunoglobulin M
Immunoglobulin M
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...
(IgM) antibodies are produced and as these levels drop (and become undetectable) immunoglobulin G
Immunoglobulin G
Immunoglobulin G are antibody molecules. Each IgG is composed of four peptide chains — two heavy chains γ and two light chains. Each IgG has two antigen binding sites. Other immunoglobulins may be described in terms of polymers with the IgG structure considered the monomer.IgG constitutes 75%...
(IgG) levels rise and remain detectable. Upon reinfection, IgM antibodies usually do not rise again but IgG levels will increase. Thus an elevated IgM titre indicates recent primary infection, while the presence of IgG suggests past infection or immunization
Immunization
Immunization, or immunisation, is the process by which an individual's immune system becomes fortified against an agent ....
.