Immunization and Vaccines Overview

A way to protect the body from infectious diseases by introducing weakened or killed versions of the disease-causing organism. This prepares the body to fight the disease if it encounters it in the future.

A method of introducing antigens (disease-causing agents) into the body to trigger the immune response. This leads to the production of antibodies against the specific disease.

A method of providing immediate protection against a disease by introducing antibodies that are already made outside the body. This protection is temporary, as the body doesn't produce its own antibodies.

A type of vaccination that involves giving a combination of different vaccines in a single dose. This helps to streamline vaccination schedules and minimize the number of injections required.

A type of vaccine derived from weakened, but living disease-causing viruses or bacteria. They stimulate the immune system to produce a long-lasting immunity.

A type of vaccine made from viruses or bacteria that have been killed or inactivated. They are typically less effective than live vaccines and require multiple doses and boosters.

Agents used in immunization to stimulate the immune system. They can be vaccines, immunoglobulins, or antisera/antitoxins.

Biological substances that stimulate the production of antibodies against a specific disease. They are used in active immunization.

Live attenuated vaccines should not be given to individuals with weakened immune systems due to conditions like leukemia, lymphoma, cancer treatments, or pregnancy.

A protein that is produced as a result of detoxification of bacterial exotoxins. It retains antigenicity but loses its pathogenic properties. The body produces antibodies against the toxoid, neutralizing the toxins produced during infection but not the bacteria itself.

A substance added to a vaccine to enhance its potency and improve the immune response to the antigen.

A combined approach to immunity where both passive and active immunization are used to provide immediate protection and long-lasting immunity.

The specific route through which a vaccine is administered. Different vaccines may require different delivery methods to ensure optimal effectiveness.

A primary vaccination regimen, typically involving a single dose, used for vaccines like BCG, measles, mumps, rubella, and yellow fever.

A primary vaccination regimen involving multiple doses, commonly used for vaccines like polio, DPT, and hepatitis B.

A booster dose, intended to maintain immunity levels after a decline due to the passage of time. Used for vaccines like DT, MMR, and others.

A comprehensive program established by the WHO in 1974 to protect children globally against six vaccine-preventable diseases. It has expanded to include a wider range of vaccines.

An event caused by the inherent properties of the vaccine when given correctly. This is a direct consequence of the vaccine itself.

An event caused by an error in the preparation, handling, or administration of the vaccine.

An event that occurs after immunization but is not related to the vaccine. It's simply a coincidence that the event happened after vaccination.

An event caused by anxiety or pain from the injection itself, rather than the vaccine itself.

A process where immune cells with Fc receptors kill target cells coated with antibodies.

A type of immune cell that can kill target cells directly, without the need for prior sensitization.

A protein that forms pores in the membranes of target cells, leading to their destruction.

An enzyme that enters target cells through pores created by perforin and triggers programmed cell death.

A type of cytokine that plays a key role in activating the immune system.

A type of interferon produced by virus-infected leukocytes, mainly responsible for antiviral defense.

A type of interferon produced by virus-infected fibroblasts, crucial for early antiviral response.

A type of interferon produced by activated T-cells and NK cells, regulates the immune response.

The transfer of living cells, tissues, or organs from one part of the body to another or between individuals.

A transplant from one part of the body to another part of the same individual.

A transplant between individuals of the same species.

A transplant between individuals of different species.

The inability of the recipient's immune system to recognize the transplanted tissue as 'self' leading to its rejection.

A severe and rapid rejection of the transplanted organ occurring within minutes to hours.

A rejection occurring within the first few weeks to months after transplantation.

The primary function of the cell-mediated immune response is to eliminate intracellular pathogens, such as viruses and bacteria, as well as tumor cells.

Both antigen-specific cells (like cytotoxic T cells (CD8+) and helper T cells (TH)) and non-specific cells (macrophages (MØ), neutrophils, and natural killer (NK) cells) participate in the cell-mediated immune response.

The cell-mediated immune response relies on the interactions of T cells with specific antigens presented by major histocompatibility complex (MHC) molecules.

Cell-mediated immunity plays a role in harmful conditions, such as type IV hypersensitivity reactions (like contact dermatitis), graft rejection, and autoimmune diseases.

Cell-mediated cytotoxicity is directly mediated by cytotoxic T cells, natural killer cells, and activated macrophages, which destroy target cells.

Delayed hypersensitivity (DTH) is a type of immune response characterized by a delayed reaction to an antigen, often involving inflammation and tissue damage.

Cell-mediated immunity is crucial for combating infections caused by obligate and facultative intracellular parasites, such as bacteria (tuberculosis, leprosy, listeriosis, brucellosis), fungi (histoplasmosis, coccidiomycosis, blastomycosis), and parasites (trypanosomiasis).

DiGeorge syndrome highlights the importance of cell-mediated immunity. Individuals with this condition lack a thymus, resulting in impaired T-cell development and deficient T-cell mediated immunity, leaving them vulnerable to intracellular infections.

Cytotoxic T cells recognize antigen on the surface of virus-infected cells, tumor cells, and allograft cells in conjunction with MHC I, secreting lymphokines and destroying the target cells.

Helper T cells release lymphokines (biological mediators) when presented on surfaces of macrophages or other cells complexed with MHC II molecules, activating macrophages and killing intracellular parasites.

Cytokines are signaling proteins and glycoproteins that mediate cell communication, acting as messengers to regulate immune, inflammatory, and reparative host cell responses.

Interleukin 1 (IL-1) is a cytokine that stimulates T cells, promotes B-cell proliferation, enhances neutrophil chemotaxis, and contributes to fever.

IL-2, a cytokine, modulates the immune response, activates T and B lymphocytes, and stimulates cytotoxic T cells and natural killer cells.

IL-10 and IL-13 are predominantly inhibitory cytokines that suppress inflammatory cytokine production by macrophages.

MHC molecules are encoded by a cluster of genes located on chromosome 6 in humans, collectively called the MHC locus. These genes are divided into three classes: Class I, Class II, and Class III, each with distinct functions and expressed proteins.

MHC class I molecules are present on the surface of all nucleated cells, including platelets. They present foreign antigens that are degraded inside the cell (endogenous pathway) to CD8+ T cells, triggering a cytotoxic response.

MHC class II molecules are mainly found on Antigen Presenting Cells (APCs) like macrophages, dendritic cells, and B cells. They present exogenously derived antigens (from outside the cell) to CD4+ T helper cells, initiating a broader immune response.

Antigen Presenting Cells (APCs) are immune cells that capture and process antigens from the environment, then present them to T cells via MHC molecules. This initiates the T cell response and adaptive immunity.

T helper cells (TH cells) are a type of T cell involved in activating and regulating other immune cells. They recognize foreign antigens presented by MHC class II molecules on APCs, releasing signals that ultimately lead to the production of antibodies and enhance other immune responses.

Cytotoxic T cells (Tc cells) are a type of T cell specifically designed to kill infected cells. They recognize antigens presented by MHC class I molecules, directly binding and destroying infected cells.

The antigen-binding cleft of MHC molecules is a groove on the extracellular portion of the MHC protein that binds to and holds the antigen fragment, enabling recognition by specific T cells.

In human, MHC complex is known as human leukocyte antigen (HLA) complex, as it was first identified on leukocytes. However, it is present on all nucleated cells.

Bare Lymphocyte Syndrome is a rare genetic disorder where a defect in the TAP (transporter associated with antigen processing) protein prevents efficient delivery of antigens to MHC class I molecules. This results in compromised cytotoxic T cell function and increased susceptibility to infections.

Superantigens are potent toxins produced by some bacteria or viruses that can activate a large proportion of T cells indiscriminately, leading to a massive immune response that can be harmful, often causing cytokine storms and immune system dysregulation.

MHC molecules play a crucial role in immune tolerance, ensuring the immune system does not attack the body's own tissues. During T cell development, self-peptides are presented by MHC molecules to ensure self-reactive T cells are eliminated or deactivated.

MHC class I molecules play a vital role in cell-mediated immunity by presenting foreign antigens to cytotoxic T cells. This triggers a specific immune response to eliminate infected cells.

MHC class II molecules play a crucial role in adaptive immunity by presenting processed antigens to T helper cells. This triggers the activation of other immune cells, including B cells, leading to a broader and more effective immune response.

Transplant rejection is a complex process where the recipient's immune system recognizes and attacks the donor's tissue as foreign. Differences in MHC genes between donor and recipient contribute significantly to transplant rejection, highlighting the importance of MHC matching for successful transplantation.

T-dependent antigens are antigens that require the help of T helper cells for antibody production. These antigens, often proteins, are processed and presented by APCs to TH cells, activating them to help B cells produce antibodies.

T-independent antigens can directly stimulate B cells to produce antibodies without the need for T cell assistance. These antigens, often polysaccharides or lipopolysaccharides, can activate B cells directly, but usually lead to a weaker immune response.

A long-term rejection that can occur months or even years after transplantation. It's characterized by a complex interplay of both cellular and humoral mechanisms that gradually damage the transplanted tissue. Over time, chronic rejection can lead to fibrosis, scarring, and eventual failure of the transplanted organ.

The process of identifying the specific HLA antigens present on the surface of a person's leukocytes (white blood cells). This helps match donors and recipients based on their HLA compatibility. This is a critical step in organ transplantation to minimize the risk of rejection.

A laboratory test used to assess the compatibility between a donor and recipient for organ transplantation. It involves mixing lymphocytes from the recipient and donor in a culture. The cells are observed for signs of immune response, such as proliferation or cytotoxicity, which can indicate the likelihood of rejection.

A laboratory test used to screen for preformed antibodies against donor HLA antigens in the recipient before transplantation. These antibodies are already present in the recipient's body and can cause hyperacute rejection.

A serious complication that can occur after bone marrow transplantation. It happens when the donor's immune cells (T cells) recognize the recipient's tissue as foreign and attack it. This can lead to damage to various organs, including skin, liver, and intestines.

A type of GVHD that occurs within days to weeks after bone marrow transplantation. It's characterized by a widespread rash, jaundice, gut ulceration, and bloody diarrhea.

A type of GVHD that may occur insidiously or follow an acute episode. It's characterized by long-term complications, such as skin damage, liver problems, and esophageal strictures. It can be life-threatening.

Drugs that suppress the immune system to reduce the risk of rejection after organ transplantation. These drugs work by interfering with the immune cells' ability to recognize and attack foreign tissue.

A powerful immunosuppressive drug that inhibits the production of certain immune signaling molecules, preventing the activation of T cells. It's commonly used to prevent rejection after organ transplantation.

A type of immunosuppressive drug that interferes with the production of DNA, inhibiting the proliferation of immune cells. It's used to prevent rejection after organ transplantation.

A type of immunosuppressive drug that blocks the activation of T cells by preventing their interaction with co-stimulatory molecules. It's used to prevent rejection after organ transplantation.

Antibodies that target specific immune cells or molecules, effectively 'knocking out' specific components of the immune system. These antibodies are used to prevent rejection after organ transplantation.

Certain anatomical locations in the body where the immune system is less active or suppressed, allowing for the survival of foreign tissue without rejection. Examples include the cornea of the eye and the fetus during pregnancy.