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Immunization
Published in Julius P. Kreier, Infection, Resistance, and Immunity, 2022
Michael F. Para, Susan L. Koletar, Carter L. Diggs
The clonal expansion and activation of lymphocytes of the various subsets result in the production of multiple types of effector systems. There may be multiplication of B lymphocytes with production of immunoglobulin directed against the antigenic determinants in the vaccine. The mechanisms of action of antibodies include direct neutralization of toxins (as in control of diphtheria), opsonization of pathogens (as in control of pneumococcal infections), complement-dependent microbial lysis (as in meningococcal infections), neutralization of viral infectivity (as in control of hepatitis B infection), and antibody-dependent cellular toxicity (as in the control of Salmonella typhi infections). Any or all of these effector mechanisms can in theory operate individually or collectively depending on the nature of the pathogen, the stage of the immune response, and other factors. Initial immunization also induces memory cells which promote a rapid secondary immune response at the time of exposure to the pathogen.
Some thoughts on infectious diseases
Published in Hugh McGavock, Dennis Johnston, Treating Common Diseases, 2017
Hugh McGavock, Dennis Johnston
For millions of years before modern medicine, the human body has been invaded by a wide range of other living organisms - micro-organisms (such as viruses, bacteria and yeasts), single-celled protozoans (such as malaria), and a variety of larger parasites which invade the skin, intestine, liver, lung, muscle and brain. The powerful human immune system produces specific antibodies which circulate in the bloodstream and, working together with cell-mediated immunity, destroy viruses, bacteria and yeasts wherever they have lodged, ensuring recovery in the majority of cases. Following the infection, ‘memory cells’ in the immune system carry a residual immunity for each specific infection, and this often lasts for years. Modern vaccination schedules (see BNF, Chapter 14.1) ensure that, by the age of 5 years, the majority of western populations have high levels of immunity to the most dangerous, life-threatening infections such as diphtheria, tetanus and poliomyelitis, and to infections that seldom kill but which can have serious sequelae (after-effects) in a minority of patients, such as mumps, measles and whooping-cough.
A Review of Classic Physiological Systems
Published in Len Wisneski, The Scientific Basis of Integrative Health, 2017
When a B cell encounters an offending antigen, it transforms into a plasma cell, which secretes substances called immunoglobulins (IgG, IgA, IgM, IgD, and IgE). These are antibodies. They bind to the pathogen and, along with other immune system components, inactivate it. IgG is the most common, comprising 75%–85% of the total serum immunoglobulin. Typically, a blood test is used to measure these antibodies, but IgA, for example, is produced in and can be measured from saliva. Memory B cells are a type of memory cell with the capacity to remember previous exposure to an antigen and, thus, to hasten the immune response upon a subsequent encounter. Both memory B cells and memory T cells are efficient immune response cells. The cells are stored in the lymphatic tissue, waiting for a returning invader. Vaccines permit an initial, relatively mild exposure to an antigen, but they result in storage of the memory cells that can later prevent the illness.
Mechanisms of cellular and humoral immunity through the lens of VLP-based vaccines
Published in Expert Review of Vaccines, 2022
Hunter McFall-Boegeman, Xuefei Huang
As with T cells, once the infection is eliminated most of the antibody generating plasma cells are eliminated. This leaves behind a small population of memory B cells capable of quickly responding to secondary infection. Even after the contraction, there is a small population of plasma cells that remain and secrete antibodies. VLP-based vaccines generate particularly high long-term titers, suggesting they are uniquely capable of eliciting long-lived plasma cells, although the exact reasoning is unknown. There is some evidence that factors beyond valency and density may be the cause[172,173]. Upon re-infection, the memory B cell population can expand and differentiate into new plasma and memory cells. Memory B cells elicited by VLP-based vaccines are able to respond to secondary challenges as measured by IgG titers following a long-term booster[174].
Understanding modern-day vaccines: what you need to know
Published in Annals of Medicine, 2018
Volker Vetter, Gülhan Denizer, Leonard R. Friedland, Jyothsna Krishnan, Marla Shapiro
Vaccines, like natural infections, act by initiating an innate immune response, which in turn activates an antigen-specific adaptive immune response [3]. Innate immunity is the first line of defence against pathogens that have entered the body. It is established within a few hours but is not specific for a particular pathogen and has no memory [4]. Adaptive immunity provides a second line of defence, generally at a later stage of infection, characterized by an extraordinarily diverse set of lymphocytes and antibodies able to recognize and eliminate virtually all known pathogens. Each pathogen (or vaccine) expresses (or contains) antigens that induce cell-mediated immunity by activating highly specific subsets of T lymphocytes and humoral immunity by stimulating B lymphocytes to produce specific antibodies [3]. After elimination of the pathogen, the adaptive immune system generally establishes immunological memory. This immunological memory – the basis of long-term protection and the goal of vaccination – is characterized by the persistence of antibodies and the generation of memory cells that can rapidly reactivate upon subsequent exposure to the same pathogen [3].
An overview of in silico vaccine design against different pathogens and cancer
Published in Expert Review of Vaccines, 2020
Kimia Kardani, Azam Bolhassani, Ali Namvar
A vaccine must be immunogenic in nature and is able to stimulate potent humoral and cellular immune responses leading to the generation of the memory cells against pathogenic epitopes. Low immunogenicity is one of the major disadvantages of peptide-based vaccines; thus, the determination of the immunogens is the critical step [139]. The immunogenicity and antigenicity of the epitopes could be predicted by several web servers [18,140] as indicated in Table 7. For example, VaxiJen web server is the first server to predict subunit vaccines, tumor antigens, and protective antigens [140]. Recently, VaxiJen (VaxiJen 2.0 version) applied the models to recognize immunogens in fungi, parasites, viruses, bacteria, and tumors [141].