Understanding Immunity and Immune System Functions
a) Immunity is the state of resistance or protection of the organism to an infection caused by a particular antigen. The immune system is a complex network of cells and proteins that defends the body against infection. When talking about the organisms that take part in this system there are many.
Regarding the organs, they are divided into primary lymphoid organs and secondary lymphoid organs. Those included in primary lymphoid organs are the bone marrow and thymus. Indeed, cells of the immune system originate in and mature here. The ones included in the secondary lymphoid organs are lymph nodes, the spleen, the tonsils and certain tissue in various mucous membrane layers in the body (for instance in the bowel). These organs are not for cell development, the cells of the adaptive immune system recognize the pathogens here.
The most common cells of the immune system can be categorized as lymphocytes (T cells, B cells, and NK cells), neutrophils, and monocytes/ macrophages. These are all types of white blood cells.
The major proteins of the immune system are predominantly cytokines (a type of hormone responsible for communication between cells of the immune system), antibodies (immunoglobulins), and complement proteins.
b) There are two different types of acquiring immunity:
– Natural or innate immunity. It occurs from birth for the inherent reasons of each species or individual. Individuals with innate immunity to a particular antigen neutralize that antigen by using primary defense barriers or non-specific innate immune mechanisms (secondary) without the need to activate an adaptive immune response.
– Acquired immunity or adaptive. This type of immunity is developed as a result of the activation of specific adaptive immune mechanisms. It lasts for a certain amount of time thanks to immune memory. The development of adaptive immunity is called immunization and can be active or passive.
c) Is the lack of specific immune response against foreign antigens. It has its origins in a dysfunction of the immune system; this dysfunction causes a low intensity immune response or lack of response as a result, infections are more common and more severe. It could be highlighted that there are two types of immunodeficiencies. AIDS caused by HIV or ‘bubble children’ with congenital immunodeficiency syndrome are examples of immunodeficiencies.
a) The regions of the immunoglobulin are constant and variable regions, along with the light and heavy regions.
* The antigen binding site is also known as paratope.
(An immunoglobulin is an antibody that is part of the immune system, a protein in the globulin group. In the presence of stranger particles or pathogens in the body, B lymphocytes synthesize immunoglobulins.
The action of immunoglobulins consists in identifying the distinctive molecules of pathogens (antigens).)
b) The regions that know the antigen are variable (Fab regions). However, the constant regions (Fc) don’t know the antigen, as it is very similar in all antibodies.
c) Vaccines basically promote the synthesis of antibodies, by inserting previously to the infection the attenuated antigen directly into the body.
That way, the immune system would be able in the future to fight against bacteria and viruses better, as they would recognize the antigen and will know exactly what kind of antibody is created against it.
a) Vaccines stimulate the body to produce its own immunity to a specific disease, but serum therapy takes disease-fighting chemicals (antibodies) from the blood of recovered patients and transfers them to the sick to boost their defenses.
b) A vaccine is a biological preparation that provides active acquired immunity to a particular infectious or malignant disease. A vaccine typically contains an agent that resembles a disease-causing microorganism and is often made from weakened or killed forms of the microbe, its toxins, or one of its surface proteins. The agent stimulates the body’s immune system to recognize the agent as a threat, destroy it, and to further recognize and destroy any of the microorganisms associated with that agent that it may encounter in the future.
Antiserum is a blood serum containing monoclonal or polyclonal antibodies that is used to spread passive immunity to many diseases via blood donation (plasmapheresis). Serum therapy, also known as serotherapy, describes the treatment of infectious disease using the serum of animals that have been immunized against the specific organisms or their product, to which the disease is supposedly referable.
c) Vaccines -> active immunity because they are used to stimulate the body’s natural defense mechanisms.
Serums -> inactive immunity antibodies against a specific infectious microorganism (or toxin produced by a microorganism) are administered directly to the person.
a) An allergen is the hypersensibility reaction to one substance that the body doesn’t tolerate. Hypersensitivity is a specific immune response that occurs disproportionately when non-pathogenic and non-harmful antigens called allergens are introduced in the body.
For example, there are allergies to pollen, dust mites, some medications or antibodies, certain foods…
b) Firstly, there is the primary immune response. Under the influence of TH lymphocytes, B lymphocytes are activated and produce IgE type antibodies. These antibodies bind to the surface of basophils and mast cells.
Secondly, there is the secondary immune response. The allergen binds to the surface IgEs of basophils and mast cells and, as a result, large amounts of histamine are released. Histamine triggers an excessive immune response.
The generalized allergic reaction is called anaphylaxis; sometimes, it can cause death due to hypotension, heart failure, or bronchial collapse. This reaction is called anaphylactic shock.
Finally, the contents of histamine-loaded mast cell granules and leukotrienes are released.
c) Examples of cell type involved in those processes: basophils, eosinophils, monocytes, T lymphocytes, B lymphocytes… Examples of biomolecules: IgEs, cytokines
a) One of the biggest problems that can occur after an organ transplant is rejection. Rejection occurs when the recipient’s immune system recognizes the transplanted organ and the antigens as foreign and attacks it. The body’s immune system is designed to protect against foreign invaders such as viruses and bacteria, but it can also mistakenly identify transplanted organs as foreign and attack them.
b) After an organ transplant, the recipient’s immune system may recognize the transplanted organ as foreign and mount an immune response against it. The molecules that provoke rejection are known as antigens, which are typically present on the surface of cells and tissues. In the case of organ transplantation, the antigens that are most important in provoking rejection are called human leukocyte antigens (HLAs).
The cells that are attacked first during rejection are typically the endothelial cells that line the blood vessels in the transplanted organ. These cells express high levels of HLAs and are in direct contact with the recipient’s immune cells. When the recipient’s immune cells recognize the foreign HLAs on the endothelial cells, they may begin to attack and damage these cells, leading to inflammation, blood clots, and ultimately, damage to the transplanted organ.
c) To prevent rejection, recipients of organ transplants are typically given immunosuppressant medications, which work to suppress the immune system’s response to the transplanted organ. However, these medications can also leave the recipient vulnerable to infections and other complications.
d) Organ transplantation is the surgical procedure of replacing a damaged or diseased organ with a healthy one from a donor. The type of transplant performed depends on the organ that is being transplanted. Here are some of the most common types of organ transplants:
Autograft: The organ belongs to the same person who has the transplant. The main advantage of this transplant is that it does not cause rejection or ethical problems. The most common auto-grafts are skin grafts.
Allograft: The organ belongs to a person with a different genetic composition. It is the most common transplant. Today, almost all organs and tissues are transplanted: skin, cornea, kidney, heart, liver, lungs, and so on.
Isograft: The organ belongs to a person who is genetically identical to the recipient and therefore does not have a rejection problem. One problem of this type of transplant is that it can only be done in the case of identical twins.
Xenograft: The organ belongs to an individual of another species than the recipient. This type of transplant is in the experimental phase and causes many ethical issues.
a) An antibody (Ab), that are glycoproteins, also known as an immunoglobulin (Ig), is a large, Y-shaped protein used by the immune system to identify and neutralize foreign objects such as pathogenic bacteria and viruses. The antibody recognizes a unique molecule of the pathogen, called an antigen.
An antigen (Ag) is any molecule, molecular structure, foreign particulate matter, or pollen grain that can bind to a specific antibody or T-cell receptor. The presence of antigens in the body may trigger an immune response. Antigens are mainly proteins, peptides (amino acid chains), polysaccharides (chains of simple sugars), lipids, or nucleic acids.
Antibodies are composed of protein chains with a special Y-shaped conformation. Antigens are usually proteins or polysaccharides. This includes parts of bacteria (capsule, cell wall, flagella, fimbriae, and toxins), viruses and other microorganisms.
b) The intermediary cells are primarily T lymphocytes, and in humoral immunity, B lymphocytes created by antibodies.
c) They are also called antibodies. In the presence of stranger particles or pathogens in the body, B lymphocytes synthesize immunoglobulins.
The Fab part of the molecule is where the antigens bind to it, called paratope.
a) A type of immunity that occurs when a person receives antibodies instead of producing them in their immune system. For example, passive immunity occurs when a baby receives the antibodies from the mother through the placenta or breast milk. Passive immune therapy consists of several different therapies, convalescent plasma, hyperimmune globulin, and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) neutralizing monoclonal antibodies.
b) Artificially acquired passive immunity is immediate but short-term immunization provided by injection of antibodies, such as gamma globulin, that are not produced by the recipient’s cells. This is known as serum therapy for immunization. The antibodies are developed in another individual or animal and then injected into another individual.
c) The form of immunity that is aroused by exposure to a foreign antigen is called active immunity, because the immunized person plays an active role in responding to the antigen. In other words, the organism itself produces antibodies and defends against threats, by humoral and cellular responses. The humoral and cellular immune responses work together to provide a coordinated defense against pathogens. The humoral response is important for neutralizing extracellular pathogens, while the cellular response is important for destroying infected cells and controlling intracellular pathogens.
d) Immunological memory ‘is the ability of the immune system to activate rapidly after a second encounter with a microbe. That is to say, in the primary immune response, it may not be strong enough to completely eliminate the pathogen, and the individual may become sick. However, upon subsequent exposure to the same pathogen, the immune system can mount a faster and more effective response, which can prevent the individual from getting sick again.
a) Rejection can occur after a transplant when the recipient’s immune system recognizes the transplanted organ as foreign and mounts an immune response against it.
Xenotransplantation is any procedure that involves the transplantation, implantation or infusion into a human recipient
The four different types are: living donation, deceased donation, tissue donation and pediatric donation.
Rejection can occur even if the donor is a close genetic match, such as a sibling or a twin. While siblings and twins may have a closer genetic match than unrelated individuals, they still differ in their human leukocyte antigens (HLAs), which are proteins that help the immune system recognize self from non-self. As a result, the recipient’s immune system may still recognize the transplanted organ as foreign and mount an immune response against it.
However, in general, the closer the genetic match between the donor and recipient, the lower the risk of rejection.
b) To prevent rejection, recipients of organ transplants are typically given immunosuppressant medications, which work to suppress the immune system’s response to the transplanted organ. However, these medications can also leave the recipient vulnerable to infections and other complications.
c) The main barrier to successful xenotransplantation is the immune response of the recipient to the transplanted organ. The immune system recognizes and attacks foreign cells and tissues, and in the case of xenotransplantation, the recipient’s immune system may recognize the donor organ as foreign and mount an immune response against it, leading to rejection of the transplanted organ.
To overcome this immune barrier, researchers have been exploring ways to modify the donor organs to make them less likely to be recognized as foreign by the recipient’s immune system. One approach involves genetically engineering the donor animal to express human proteins on its cells and tissues, which may make the donor organs less recognizable as foreign by the recipient’s immune system. Other approaches involve using immunosuppressive medications or other strategies.
a) Serum contains a variety of proteins, including antibodies, which are produced by the immune system in response to the presence of foreign substances, such as bacteria, viruses, or toxins.
Serum can be collected from individuals who have been exposed to a specific pathogen or toxin and have developed an immune response against it.
The use of serum as a form of immunization is known as passive immunization. Passive immunization involves the administration of preformed antibodies, such as those found in immune serum, to an individual to provide immediate protection against a specific pathogen or toxin.
b) Vaccines are biological preparations that contain a weakened or inactivated form of a disease-causing microorganism, or a piece of the microorganism, such as a protein or sugar. When a person is vaccinated, their immune system is exposed to the vaccine and produces an immune response against the microorganism or its piece contained in the vaccine.
The immune response produced by the vaccine allows the body to recognize and defend itself against the disease-causing microorganism in the future, preventing the person from becoming sick or reducing the severity of the illness.
Vaccines are typically administered by injection, but they can also be administered orally or intranasally. The timing and frequency of vaccine administration depends on the type of vaccine and the disease being prevented.
The immunity acquired through vaccination is known as active immunity, as the person’s immune system is actively responding to the vaccine and producing an immune response. Active immunity can be long-lasting, providing protection against the disease for years or even a lifetime, depending on the vaccine.
c) Vaccination is the active method of immunization preferred for preventing infectious diseases because it provides long-term protection and can help prevent the spread of disease in the community. Serum is the passive immunization typically used in situations where immediate protection is needed, such as in the treatment of individuals who have been exposed to a highly infectious disease or toxin, or in the prevention of diseases in individuals who are at high risk of infection and have not yet developed their own immune response.
d) When a pregnant woman is vaccinated, some of the antibodies produced by her immune system in response to the vaccine can be transferred to the fetus through the placenta. This transfer of antibodies provides passive immunity to the fetus, as the baby is not actively producing an immune response but is instead receiving pre-formed antibodies from the mother.
a) – Natural or innate immunity. It occurs from birth for the inherent reasons of each species or individual. Individuals with innate immunity to a particular antigen neutralize that antigen by using primary defense barriers or non-specific innate immune mechanisms (secondary) without the need to activate an adaptive immune response.
– Acquired immunity or adaptive. This type of immunity is developed as a result of the activation of specific adaptive immune mechanisms. It lasts for a certain amount of time thanks to immune memory. The development of adaptive immunity is called immunization and can be active or passive.
– Active immunity is a type of immunity that is acquired through exposure to a foreign substance, such as a pathogen or vaccine. It involves the activation of the body’s immune system and the development of a specific immune response, which can provide long-lasting protection against future exposures to the same substance.
– Humoral immunity, also known as antibody-mediated immunity, is a type of adaptive immunity that involves the production of antibodies by B cells in response to an antigen. It is called ‘humoral’ because it involves the action of substances found in the blood or other bodily fluids, called ‘humors’.
– Cellular immunity, also known as cell-mediated immunity, is a type of adaptive immunity that involves the activation of T cells to recognize and destroy infected or abnormal cells. It is called ‘cellular’ because it involves the action of cells of the immune system, rather than the production of antibodies like in humoral immunity.
b) A person is considered seropositive for a disease-causing virus if they have detectable levels of antibodies against that virus in their blood. Seropositivity indicates that a person has been exposed to the virus at some point in the past and has mounted an immune response to it, either through natural infection or vaccination.
c) Is the lack of specific immune response against foreign antigens. It has its origins in a dysfunction of the immune system; this dysfunction causes a low intensity immune response or lack of response as a result, infections are more common and more severe. It could be highlighted that there are two types of immunodeficiencies. AIDS caused by HIV or “bubble children” with congenital immunodeficiency syndrome are examples of immunodeficiencies.
d) Breastfeeding has several immunological benefits for the baby, as breast milk contains a wide range of antibodies (IgG, IgM, IgA, IgD, and IgE) that help protect the baby against infections and support their immune system development. Here are some of the main immunological benefits of breastfeeding:
– Passive immunity: Breast milk contains high levels of immunoglobulins, particularly IgA, which can help protect the baby against a variety of infections.
– Anti-inflammatory factors: Breast milk contains anti-inflammatory factors such as cytokines and growth factors that help reduce inflammation and promote tissue healing.
– Prebiotics and probiotics: Breast milk also contains prebiotic fibers that help promote the growth of beneficial bacteria in the baby’s gut
– Immune cells: Breast milk contains immune cells such as leukocytes, which can help protect the baby against infections and support their immune system development.
a) When an organism receives a transplant of an organism of an organ from another person, the body’s immune system may recognize the new organ as foreign and attempt to reject it. This happens because the immune system is designed to protect the body from foreign invaders, including cells from other people’s bodies.
Type of transplants: living donation, deceased donation, tissue donation and pediatric donation
The immune system has a way of identifying which cells belong to the body (self) and which are foreign (non-self). This is done through a complex system of proteins called human leukocyte antigens (HLAs) that are present on the surface of every cell in the body. When the immune system detects cells with HLAs that are not recognized as self, it triggers an immune response to attack and eliminate them.
Immunosuppressive medications are drugs that suppress the immune system and are commonly used to prevent or treat rejection in organ transplantation. These drugs work by blocking the activity of certain immune cells or by interfering with the signaling pathways involved in immune responses.
b) If one twin needs an organ transplant, the other twin may be considered as a potential donor. In this case, the twin would be an HLA (human leukocyte antigen) identical match, which is the most ideal type of match for transplantation. HLA are proteins found on the surface of cells in the body that are used by the immune system to distinguish between self and non-self. Because identical twins have the same HLA profile, they are the best match for each other and have a much lower risk of rejection.
It’s important to note that organ transplantation is a complex and individualized process, and the decision to use a sibling as a donor will depend on a number of factors, including the specific medical situation and the compatibility of the donor and recipient.