Medical Glossary
2
2D Immunoblotting
Immunoblotting is a technique that allows researchers to detect specific proteins in a sample. Proteins are applied to a gel and separated according to their length or 3D structure using a method called gel electrophoresis, where an electric current runs through the gel. Proteins are then transferred to a special membrane and made visible using antibodies that bind to the protein(s) in question and are linked to a colourful dye. This allows scientists to determine which proteins are present and in what quantity.
A
Acellular vaccines
Acellular vaccines only contain parts of a bacterium, in contrast to 'whole cell vaccines', which contain the whole bacterium.
Adaptive immune response
The adaptive immune response is the body's specific response to an invader, such as a bacterium or virus, that is triggered a couple of days after an infection occurs. The adaptive immune response is activated by cells involved in the innate response, and is usually mediated by B-cells and T-cells. This response is specific to the invader and is usually able to clear the infection completely, although this can take a couple of days as cells have to be activated, and messenger molecules and antibodies have to be produced.
Adenovirus
Adenoviruses are widespread, and are often responsible for illnesses such as the common cold. However, researchers have now managed to change them in a way that renders them harmless so that they can no longer cause disease. They can be made so they produce proteins from other organisms such as bacteria. That way they can act as vaccines to protect against those bacteria.
Affinity Chromatography
Affinity Chromatography describes the process of purifying a protein, by using a specific property of that same protein (e.g. its shape). A solution containing the protein in question is passed through a column filled with a selecting agent (e.g. an antibody that can bind specifically to that protein's shape) and while most of the solution is passed through the column, the protein binds to the antibody and is withheld until later, thus, it is purified.
Ampicillin
Ampicillin is an antibiotic related to penicillin, and is very good at killing bacteria (including gram-negative bacteria such as Neisseria meningitidis and Haemophilus influenzae, which are otherwise difficult to kill). Ampicillin, like penicillin, damages the bacterial cell wall and causes the bacterium to die.
Antibiotic
An antibiotic is a substance that can prevent bacteria from growing (NOT viruses) and, therefore, can be used to treat bacterial infections. Antibiotics were introduced in the 1930s and have been used since to successfully treat most bacterial infections. They are usually derived from plants and fungi, but there are now a number of synthetic antibiotics as well. Antibiotics do not harm human cells and, therefore, are safe to use. However, over the years bacteria have become resistant to some types of antibiotics (i.e. MRSA), which necessitates more research into new types of antibiotics.
Antibody
An antibody is a structure produced by the body's immune system to fight and neutralise intruders such as bacteria and viruses. Antibodies are produced by specific cells of the immune system called B-cells. They are secreted into the blood where they bind proteins, or 'antigens', that are found on the surface of bacteria and viruses.
Antigen (antigenic)
An antigen is a type of structure that exists on the surface or within bacteria and viruses (as well as existing on normal human cells). Generally, each type of bacterium or virus will have specific antigens; therefore, by identifying the antigen, scientists are able to identify the bacteria or virus. Antigens are also the structures that are targeted and bound by antibodies that are produced by the immune system in order to fight an infection. However, because antigens are usually unique to a specific bacterium or virus, antibodies produced by the body to attack one antigen cannot be used to attack another antigen. This type of immune response is called specific or adaptive immune response.
Antiserum
An antiserum is a substance, usually produced in animals, that contains antibodies against a bacterium or virus and can be administered to a patient infected with that bacterium or virus to help fight disease. Antisera are produced by infecting an animal, such as a horse or rabbit, with the bacterium or virus. The animal then has an immune response and its blood will contain antibodies and other immune cells against the bacterium or virus it was infected with. These antibodies are then separated from the animal's blood and used to treat patients. This type of treatment was mainly used in the early 1900s and has now been replaced by antibiotic and antiviral treatments.
Apoptosis
Host cell death
Assay
An assay is a method used in microbiology to measure and test the effect of a vaccine, a drug, or another substance in an organism or sample (e.g. a blood sample or serum sample)
B
B cells / B Lymphocytes
B cells or 'B-lymphocytes' - alongside -T-cells - are the immune cells responsible for the adaptive immune response, which is tailored to the specific bacterium or virus infecting the body. B-cells produce 'antibodies' that recognise and bind to bacteria or viruses, rendering them useless. B-cells also produce 'memory cells', which lie dormant in the body until the individual encounters the bacterium or virus again. These cells can then initiate a quick and specific response to prevent illness.
Bactericidal
A bactericidal agent can kill bacteria
Bacteriostatic
A bacteriostatic agent can inhibit bacteria, so they are no longer able to cause disease. However, bacteriostatic agents do not kill bacteria. A bactericidal agent can kill bacteria.
Biosynthesis
Biological production or the making of proteins by an organism.
Bivalent (7-valent; 13-valent)
In medicine, bivalent or multivalent vaccines are vaccines that contain antigens from multiple bacteria or viruses and, therefore, can stimulate immunity against several bacteria or viruses in one vaccination.
C
Capsule
The outer shell around bacterial cells. Capsules often play important roles in the immune response, as the immune system is able to recognise structures within the capsule and, therefore, can identify dangerous intruders. Many vaccines contain parts of bacterial capsules in order to stimulate an immune response.
Carrier / Carriage
A carrier is an individual who carries a bacterium or virus in a defined area of the body without showing any symptoms of illness. These individuals have been colonised by a bacterium or virus and can spread it within the population (i.e. through saliva or droplets). As they do not get ill, carriers are very hard to identify and usually remain untreated.
Cellular immune response
The cellular immune response is the response regulated by T-cells, mainly involving CD4+ (a type of receptor on the cell's surface) T-cells, which regulate the immune reaction. The cellular immune response is part of the adaptive immune reaction.
Cephalosporin
Cephalosporins are antibiotics that have the same mode of action as penicillins (they damage the bacterial cell wall), but are still active against penicillin resistant bacteria. Several 'generations' of cephalosporins, with increasing potency, have been developed over the years. Third generation cephalosporins are now the most commonly used form.
Cerebrospinal Fluid
Cerebrospinal fluid (CSF) is a clear bodily fluid found inside the brain and spinal cord. Samples of CSF can be used to identify infections in the brain and spinal cord and are usually obtained through a lumbar puncture.
Chloramphenicol
Chloramphenicol is an antibiotic that inhibits bacterial protein production,thereby preventing bacterial growth. Chloramphenicol is active against a range of bacteria, including the main meningitis-causing agents Neisseria meningitidis, Haemophilus influenzae and Streptococcus pneumoniae. It is used to treat patients who are allergic to penicillin and other antibiotics.
Colonisation / Coloniser
Colonisation is the process by which bacteria and viruses inhabit a certain area of the body. Bacteria that colonise the body are called 'colonisers'. Many types of bacteria and viruses can colonise the human body. They do not usually cause disease and often remain unnoticed, thus making the colonised individual a carrier of the bacterium or virus, who can then pass the bacterium or virus on to others. Preventing colonisation is a key factor in reducing the incidence of bacteria and viruses within the population.
Commensals
Commensals are 'harmless' bacteria that occur naturally in the human body and do not cause disease. Commensals are interesting for researchers as they give clues as to what makes harmful bacteria harmful, and what allows commensals to co-exist with the human body in relative harmony
Complement
The complement system is part of the innate immune system and helps antibodies to kill bacteria by 'punching' a hole in the bacterial cell membrane. As part of the innate response, the complement response is not specific, but is activated by the adaptive response
Component vaccine
Component vaccines contain parts of microbes such as capsule or specific proteins sufficient to stimulate an immune response.
Conjugate vaccine
Conjugate vaccines contain part of the sugar (polysaccharide) coating of a bacterium combined (conjugated) with a protein. This makes the vaccine work better, giving better protection over a longer period of time. The Meningitis C vaccine in childhood immunisation is one example of a conjugate vaccine.
Cross-reactive immunity / Cross-protective immunity
Cross-reactive immunity is a situation in which one agent, for instance a vaccine against one 'serogroup' of bacterium, causes immunity against other 'serogroups'. In other words, an immune reaction against one serogroup produces 'antibodies' and 'memory cells' that are able to recognise and react against antigens from a different serogroup, therefore, immunity is 'cross-reactive'.
Cytokine
Cytokines are messenger molecules, produced predominantly by immune cells, which activate and deactivate other cells. There are numerous types of cytokines, each with different functions and each produced at different times during the immune response.
D
Dendritic cells
Dendritic cells are immune cells that are active early on in the immune response. They phagocytose intruders such as bacteria and viruses, and then activate the adaptive immune response. Dendritic cells are part of the innate immune system, right at the front line of the body's defence. They are active early on in infection and phagocytose all bacteria or viruses without discrimination. Dendritic cells then present parts of the bacterium or virus to other cells of the immune system called T- and B- cells, which can then initiate a more specific immune response.
Dexamethasone
Dexamethasone is a steroid drug that can suppress the immune system and the inflammatory response. In pneumococcal meningitis treatment, dexamethasone can be used to dampen down the immune response in order to avoid permanent damage such as hearing loss.
E
Epidemiology
The study of the distribution of a disease or the distribution of an infectious agent within the population, for example by geography, age group or gender.
G
Genetic Linkage Analysis
Genetic linkage analysis is a technique used to associate the function of each gene with its location on the genetic material (chromosomes).
Genotype
The total number of genes within the DNA of a cell forms the 'genotype'; 'genotype' can also refer to a specific gene and its DNA sequences within one organism.
H
Herd immunity
Herd immunity means that, within a large population, a small unvaccinated group of individuals can be protected from contracting a disease for which the majority of people have been vaccinated. To produce herd immunity, a large percentage (80-90%) of the population needs to be vaccinated, so that the disease can no longer spread. Consequently, unvaccinated individuals are protected because the herd (i.e. the great majority of people) is vaccinated, thus the disease is prevented from spreading. Herd immunity is an ideal situation, in which a disease can no longer persist in a population. This has been achieved for several diseases, such as smallpox, polio and MMR (measles, mumps, and rubella).
Heterologous
Genetically different
Homologous
Genetically the same
Humoral immune response
The humoral immune response is the response regulated by B-cells, mainly involving the production of antibodies. The humoral immune response is part of the adaptive immune reaction.
Hyperinvasive
A hyperinvasive organism is able to invade the human body easily, for instance, an organism that can cross from surfaces such as the nose and throat into the bloodstream or brain and causes disease. Many strains of the bacterium Neisseria meningitidis exist harmlessly in the noses and throats of individuals without causing disease. Some strains are more able than others to cross the barrier between the nose / throat and the bloodstream, causing serious disease. These strains are referred to as 'hyperinvasive'.
I
Immunity
Immunity, in medicine, is when an individual is immune, or resistant, to a disease. Generally, immunity arises either through vaccination or infection. For immunity to develop, the body's immune system needs to encounter the bacterium or virus (or a vaccine) and learn how to fight that specific intruder. The reaction in the first encounter produces 'memory cells' that enable the body to recall what happened during the first infection or vaccination. Then, if the individual encounters the bacterium or virus a second time, they won't become ill as the body can react quickly and destroy the intruder before illness occurs. The aim of most vaccines is to induce 'immunity'.
Immunodeficiency
Immunodeficiency describes a state in which an individual's immune system is weakened ('deficient'), for instance through an infectious disease (such as HIV) or an inherited genetic disorder. Immunodeficient individuals are vulnerable to disease as their immune system is not functioning properly.
Immunogenicity (immunogenic)
An immunogenic agent or protein is something that can stimulate an immune response; immunogenicity is the ability to stimulate an immune response. For example, vaccine components need to be immunogenic, so that they can cause an immune reaction, thus protecting the body from future infection.
Immunomodulatory
An immunomodulatory agent regulates the immune system's response to disease, for example, it can prevent overreactions of the immune response by suppressing certain immune cells, thus keeping them from producing messenger molecules that would otherwise activate the immune response.
In vitro
In vitro means 'in a test tube', as opposed to in a living organism, such as an animal.
In vivo
In vivo means 'in a live organism', as opposed to in a test tube.
Incidence
Incidence is a measure of the risk of developing a disease within a specified period of time. Incidence should not be confused with prevalence, which is a measure of the total number of cases of disease in a population, rather than the rate of occurrence of new cases. Thus, incidence conveys information about the risk of contracting the disease, whereas prevalence indicates how widespread the disease is.
Innate immune response
The innate response is the non-specific immune response that occurs very soon after infection. The innate response is quick and non-specific, and is usually mediated by macrophages, dendritic cells and natural killer cells. This response can often limit disease, but cannot fully clear the infection (for this an adaptive response is needed). The innate response activates the adaptive response.
Intramuscular
Intramuscular injections refer to injections that are administered directly into a muscle, for instance the thigh or upper arm.
Intranasal
Intranasal administration is when a substance is administered to the body 'through the nose'.
Intrathecal
Intrathecal means 'introduced into' or 'occurring in' the space under the arachnoid membrane of the brain or spinal cord. An intrathecal injection is an injection into the spinal canal. This route of administration is of particular importance when a drug needs to reach the brain quickly and cannot be given orally or intramuscularly, as this would take too much time.
Intravenous
Intravenous administration of a substance refers to administration directly through a vein. The intravenous route is the fastest way to introduce fluids or medications into the whole body.
L
Lipo-polysaccharide / Lipo-oligosaccharide / Polysaccharide
These are sugars, which often form the coating of bacterial cells. Poly- and oligosaccharides are specific structures that can be used in vaccines to provoke an immune response.
Lipopolysaccharide-based conjugate vaccine
A vaccine manufactured from part of the sugar coating of a bacterium, which is then linked (conjugated) to a protein to make it more potent in stimulating an immune response.
Live vaccine
Live vaccines contain whole bacteria that, usually, have been disarmed, for example through chemical or heat treatments or through prolonged growth in animals, so that they can no longer cause disease in humans.
Loci
Small part of DNA, which describes a region that contains a gene (genes are regions of DNA that can be used to produce proteins). Human DNA has a great number of different 'loci', each with a different name, so that scientists can pinpoint the location of genes on the DNA.
M
Macrophage
Macrophages are cells of the immune system that engulf and fight invaders such as bacteria and viruses. They also produce messenger molecules to regulate the immune response.
Mass Spectrometry
Mass spectrometry is a technique that allows researchers to determine the molecular structure of compounds such as peptides (small parts of proteins) and proteins. In this technique, a sample (containing, for instance, a bacterial peptide) is vaporised and ionised in the machine in order to produce charged particles, which can then be identified according to their size and positive or negative charge. This allows scientists to separate and characterise proteins and parts of proteins.
Maturation (Cell)
The process of cell maturation refers to changes occurring in a cell after it is activated and before it is 'mature' and ready to perform its task. Cells of the immune system are activated by different factors, for instance dendritic cells can become activated when they encounter a bacterium. Upon activation, cells mature, which means that they undergo changes that later allow them to fulfil their function. This can include, but is not limited to changes in their size or shape and the secretion of messenger molecules.
Meningococcus (meningococcal)
Caused by or related to Neisseria meningitidis. For example, meningitis caused by a member of the Neisseria meningitidis family (such as Neisseria meningitidis A, B or C) is described as 'meningococcal meningitis'.
Microarray Analysis
Microarrays are a relatively new laboratory technique to examine the abundance of certain genes or bits of DNA or proteins in a sample. One array can contain tens/hundreds/thousands of genes or proteins, so a single microarray experiment can accomplish many tests at the same time.
Mucosal Immunity
Mucosal immunity occurs when antibodies and 'memory cells' specifically protect the mucosal layers of the body from contracting disease. Many bacteria and viruses enter the body through mucosal surfaces (i.e. surfaces that have a mucus layer), such as the nose, mouth or genital areas. Furthermore, many bacteria (such as Neisseria meningitidis) 'colonise' these surfaces without an individual noticing. Mucosal immunity protects these surfaces, thus stopping the bacteria or viruses from colonising and entering the body in the first place. It is very difficult to stimulate mucosal immunity, but several newer vaccines are now trying to induce this type of immunity.
Mucosal vaccines
Mucosal vaccines are vaccines that are able to stimulate the immune response at mucus surfaces such as the nose and throat. These vaccines have become interesting for researchers, as the mucus surfaces of the body are often the first to come into contact with intruders such as bacteria or viruses.
Multi-component vaccine
Multi component vaccines are vaccines that consist of several components (for instance multiple parts of one bacterium or even multiple parts of two or three different bacteria) which induce a broader immune response. For example, the Diphtheria/Tetanus/Pertussis/Polio/HiB vaccine, recommended in the UK for children aged 2, 3 and 4 months, is a multi-component vaccine that protects children from several diseases at once (Diphtheria, tetanus, whooping cough, polio and Haemophilus influenzae type B meningitis).
Murine
Mouse or 'from the mouse'.
Mutant
A mutant is a version of an organism or protein that is in some way altered from the original organism or protein. Mutants can occur naturally (for example some bacteria mutate to become resistant to antibiotics) or can be created through various methods such as genetic modification or chemical treatments.
Myocardial Depression / Dysfunction
Myocardial depression is a consequence of septic shock, which is linked to septicaemia, and results in depressed (decreased) heart function. During myocardial depression, blood flow from the heart (cardiac output) is reduced, which results in lack of oxygen supply to other vital organs of the body and can be life threatening.
N
Nasopharynx
The nasopharynx is the uppermost part of the pharynx (the top part of the respiratory tract). This includes the nasal cavities and upper part of the throat.
Natural Immunity / Naturally acquired immunity
Natural immunity is when immunity is stimulated by colonisation of, or infection from, the bacterium or virus itself as opposed to immunity triggered by vaccination.
Neisseria lactamica
Neisseria lactamica is a relative of Neisseria meningitidis, but does not cause disease. Neisseria lactamica is a commensal, which is present in many healthy children without causing disease. Carriage of N. lactamica has been associated with decreased incidence of invasive meningococcal disease.
O
Outer membrane vesicle vaccine / OMV vaccine
OMV vaccines are made from small round particles that pinch off from the outer surface of some bacteria e.g. Neisseria meningitidis. They mainly consist of the outer surface of the bacterium and can be used for vaccination. Since these vesicles resemble the real bacteria, they are good at stimulating an immune response but are safe, because they do not contain any genetic material, which means they cannot properly infect cells or replicate themselves.
P
Pathogen (pathogenic)
A pathogen is an agent that can cause disease, such as a bacterium or a virus.
Pathogenesis
The mechanism by which disease is caused.
Penicillin
Penicillin destroys the cell wall of bacterial cells and causes them to die. It was discovered by Alexander Fleming in 1928. Penicillin was used extensively in the Second World War to treat wound infections in soldiers and its related drugs, ampicillin and amoxicillin, remain some of the most popular antibiotics to date.
Phagocytosis / to phagocytose
Phagocytosis is the process by which cells of the immune system 'eat' or engulf bacteria or viruses. Several different types of immune cells, such as dendritic cells or macrophages, can phagocytose intruders. These cells rearrange their shape to engulf the bacterium or virus and then 'digest' the intruder. The immune cells then present parts of the digested bacterium or virus on their outside surfaces so that other cells, such as T- and B- cells, can detect them.
Phenotype
A phenotype is a characteristic, such as size, shape, behaviour or composition etc. It can be negative or positive. For example, a positive phenotype would be Haemophilus influenzae strains making the type b capsule.
Pili
Pili are hair-like appendages found on the surface of many bacterial cells, such as Neisseria meningitidis. Pili are antigenic, which means that, in some instances, they can be recognised by the immune system and cause an immune response.
Pneumococcus (Pneumococcal)
Caused by or related to Streptococcus pneumoniae. For example, meningitis caused by Streptococcus pneumoniaeis described as 'pneumococcal meningitis'.
Prevalence
Prevalence is defined as the total number of cases of the disease in the population at a given time. It is used to assess how common a certain disease is over a defined time period.
Proliferation
Growth (especially bacterial or cellular growth).
R
Resistance (Resistant)
Resistance in an organism means that it is no longer sensitive to a drug, or an immune response, and can no longer be killed - the organism has become resistant. As bacteria and viruses can change very quickly, resistance can develop fast. This has become a well known problem for antibiotic treatments, because so many bacteria are now resistant to antibiotics.
S
Septicaemia / Bacteraemia
Septicaemia means 'infection of the blood' and occurs when an agent, such as a bacterium, manages to enter the bloodstream. Septicaemia is commonly known as 'blood poisoning' and is a life threatening condition that requires immediate treatment.
Serogroup
There are 13 serogroups of Neisseria meningitidis depending on the composition of capsule (sugar coat). The most common that cause disease are: A, B, C, Y, W-135. In the UK serogroup B is the most common. Good vaccines - based on the capusule- are available for serogroups A, C, Y and W-135.
Serum/ Sera
Sera are blood samples taken from individuals and processed by spinning in a centrifuge to only contain the cells of the immune system. (Serum is the singular of Sera).
Systemic
'Systemic' in medicine refers to something that is spread 'system-wide' or 'throughout the human body'.
T
T cells / T Lymphocytes
All types of T cells or 'T-lymphocytes' - alongside B-cells - are the immune cells responsible for the adaptive immune response, a response that is tailored to the specific bacterium or virus infecting the body. T-cells produce messenger molecules called cytokines, which can activate other cells. T-cells can also become 'killer cells' that search for and destroy cells of the human body that have been infected by a bacterium or virus. Alternatively, they can become T-regulatory cells, which regulate immune responses. T cells can also produce 'memory cells' that lie dormant in the body until the bacterium or virus are encountered again. These cells can then initiate a quick and specific response to prevent illness.
V
Vaccination / Immunisation
Vaccination or Immunisation is a process designed to induce immunity, i.e. to make individuals immune against a disease. Vaccines usually consist of dead or disarmed bacteria or viruses, or even just parts of bacteria or viruses that cannot cause disease. The vaccine causes an immune response which is very similar to that caused by a natural infection. The body produces antibodies and 'memory cells' that stay on long after the vaccination, so that if the individual then encounters the actual bacterium or virus, the body reacts quickly and the person does not get disease.
Vaccine
A vaccine is a substance that is administered to prevent disease. Vaccines are an essential part of modern medicine and have been used to wipe out diseases such as smallpox and polio. Vaccines consist of whole bacteria or viruses (either disarmed or killed) or parts of bacteria or viruses, which are able to stimulate an immune response without causing disease. If an individual later encounters the real bacterium or virus, the immune system is prepared and can react quickly, so illness is prevented.
Vaccine Candidates
Vaccines Candidates are viral or bacterial proteins that have the potential to stimulate an immune response without harming the body in the process. Ideally, vaccine candidates are safe and stimulate immunity against several different strains and serogroups.
Vancomycin
Vancomycin is an antibiotic that inhibits the production of bacterial cell wall blocks, thereby killing the bacterium. Vancomycin is only active against bacteria with specific characteristics (i.e. gram-positive bacteria) and, therefore, is not active against Neisseria meningitidis or Haemophilus influenzae, but can be used to treat Streptococcus pneumonia.
Vector
In medical research, a 'vector' is used as a vehicle to transport proteins or even genes into the body. Vectors can be produced synthetically or they can be modified, harmless viruses, such as Adenovirus.
W
Whole cell vaccine
Whole cell vaccines contain whole bacterial cells (either killed or disarmed), in contrast to 'acellular' vaccines, which only contain parts of cells.
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