Diseases Of Immunity

Anti-body mediated, mostly by binding of Fc fragments. Complement is also heavily involved in some reactions.

Prototype disorder = Anaphylaxis

Prototype disorders = transplant rejection, TB, contact dermatitis.

Food allergy is an example of an immediate hypersensitivity reaction. In this type of reaction, the immune system reacts rapidly and strongly to an allergen, such as a specific food. The reaction occurs within minutes to hours of exposure and is mediated by the release of histamine and other inflammatory molecules. Symptoms can range from mild, such as itching and hives, to severe, such as difficulty breathing and anaphylaxis. Immediate hypersensitivity reactions are typically IgE-mediated, meaning that they involve the production of specific antibodies called immunoglobulin E (IgE) in response to the allergen.

B lymphocytes mediate humoral immunity. Humoral immunity refers to the immune response that involves the production of antibodies by B lymphocytes. These antibodies are released into the body fluids, such as blood and lymph, to neutralize or eliminate pathogens. B lymphocytes, also known as B cells, are a type of white blood cell that plays a crucial role in the adaptive immune response. They recognize and bind to specific antigens, triggering the production and release of antibodies. This immune response is called humoral immunity because it involves the action of antibodies in the body fluids.

Signal 1 occurs when the T cell receptor is engaged by the appropriate MHC bound antigen and the co-receptors CD4 and CD8 bind to MHC molecules.
Signal 2 occurs when CD28 on the T cell interacts with co-stimulatory molecules (CD80 and CD86) expressed on antigen presenting cells.

CD4 molecules bind to MHC class II molecules. MHC class II molecules are found on the surface of antigen-presenting cells, such as dendritic cells, macrophages, and B cells. They present antigens to CD4+ T cells, which play a crucial role in immune responses. CD4 molecules bind to the MHC class II molecule in a specific manner, allowing for the activation of CD4+ T cells and the initiation of an immune response.

The differentiation of naive B cells into IgE secreting B cells is dependent on the activity of T-helper-2 cells.

Prototype disorder = Goodpasture Syndrome

Cell mediated (or cellular) immunity is responsible for defense against intracellular microbes. This means that this type of immune response is specifically designed to target and eliminate microbes that are able to invade and replicate within the cells of the body. Intracellular microbes include viruses, bacteria, and parasites that can infect and survive inside host cells. Cell mediated immunity involves the activation of T cells, which recognize and destroy infected cells, preventing the spread of the infection. This type of immunity is crucial in combating intracellular pathogens and preventing the development of severe infections.

Rituximab and other anti-CD20 antibodies are highly effective in therapy of B cell non-Hodgkin lymphoma. CD20 is expresse on normal and neoplastic B cells, but not on other cells.

CD8 binds to MHC class I molecules. MHC class I molecules are found on the surface of all nucleated cells and present antigens to CD8+ T cells. These antigens are usually derived from intracellular pathogens or proteins produced within the cell. CD8 binds to the MHC class I molecule in order to recognize and respond to these antigens, leading to the activation of cytotoxic T cells and the elimination of infected or abnormal cells. MHC class II molecules, on the other hand, present antigens to CD4+ T cells. MHC class III molecules are not involved in antigen presentation.

T cells can only recognize antigens that are presented on the surface of cells, which are referred to as membrane-bound antigens. This recognition occurs through the interaction of the T cell receptor (TCR) with the antigen-presenting molecule called major histocompatibility complex (MHC). Therefore, the statement that T cells can only recognize membrane-bound antigens is true.

In the central nervous system, HIV infects macrophages and microglial cells (also from monocyte/macrophage lineage).

NF-κB is the most significant transcription factor activated by signaling from toll-like receptors. Toll-like receptors play a crucial role in the innate immune response by recognizing pathogen-associated molecular patterns. Upon activation, toll-like receptors initiate a signaling cascade that leads to the activation of NF-κB. NF-κB then translocates to the nucleus and regulates the expression of genes involved in inflammation, immune response, and cell survival. Therefore, NF-κB is considered the most significant transcription factor in mediating the immune response triggered by toll-like receptor signaling.

CD8+ T cells act mainly as cytotoxic cells. Cytotoxic cells are a type of immune cells that are responsible for killing infected or abnormal cells in the body. CD8+ T cells recognize specific antigens on the surface of these cells and release toxic substances to destroy them. This process helps to eliminate pathogens, such as viruses or cancer cells, and maintain the overall health of the body.

Graves disease is an autoimmune disorder characterized by the production of antibodies that stimulate the thyroid gland, leading to the overproduction of thyroid hormones. This excessive hormone production causes symptoms such as weight loss, rapid heartbeat, and bulging eyes. Antibody-mediated hypersensitivity reactions involve the production of antibodies that target specific antigens, leading to tissue damage or dysfunction. In the case of Graves disease, the antibodies produced target the thyroid gland, resulting in its overactivity. Therefore, the correct answer is antibody-mediated.

Prototype disorder = SLE

Myasthenia Gravis is an autoimmune disorder where antibodies are produced against the acetylcholine receptors on muscle cells. These antibodies interfere with the transmission of nerve impulses to the muscles, leading to muscle weakness and fatigue. This type of immune response, where antibodies are involved in causing the disease, is known as antibody-mediated hypersensitivity reaction.

Mast cells are central to the development of immediate hypersensitivity

T-helper-2 cells are involved in the synthesis of IgE and activation of eosinophils. These cells play a crucial role in allergic responses and asthma. T-helper-2 cells produce cytokines such as IL-4, IL-5, and IL-13, which stimulate B cells to produce IgE antibodies. IgE antibodies then bind to mast cells and basophils, triggering the release of inflammatory mediators. T-helper-2 cells also promote the recruitment and activation of eosinophils, which are involved in the immune response against parasites and contribute to allergic inflammation. Therefore, T-helper-2 cells are the correct answer in this context.

Toll-like receptors (TLRs) are a type of protein receptor found on the surface of immune cells. When activated, TLRs initiate a signaling cascade that leads to the synthesis of various components of the innate immune response, such as cytokines, endothelial adhesion molecules, and nitric oxide synthase. This activation is crucial for the immune system to mount an appropriate response against pathogens and maintain immune homeostasis. TLRs recognize specific patterns on pathogens, known as pathogen-associated molecular patterns (PAMPs), and play a crucial role in initiating the immune response.

Mannose binding lectin and C-reactive protein are circulating plasma proteins that coat microbes for phagocytosis and complement activation. Phagocytosis is the process by which immune cells engulf and destroy foreign particles, such as microbes. By coating the microbes, mannose binding lectin and C-reactive protein facilitate their recognition and uptake by phagocytes, enhancing the immune response against the invading pathogens. This process is essential for the clearance of pathogens from the body and the activation of the complement system, which further enhances the immune response.

T-helper-1 (Th1) cells are involved in facilitating delayed hypersensitivity, macrophage activation, and synthesis of opsonizing and complement-fixing antibodies due to the actions of IFN-γ. Th1 cells produce IFN-γ, which activates macrophages and enhances their ability to kill intracellular pathogens. IFN-γ also stimulates B cells to produce opsonizing antibodies and promotes the activation of the complement system. Th1 cells are primarily involved in cell-mediated immune responses and play a crucial role in defense against intracellular pathogens.

Chronic granulomatous disease is a condition characterized by recurrent infections and the formation of granulomas. It can be inherited in different ways, such as being X-linked or autosomal dominant or recessive. The disease is caused by multiple molecular defects in phox genes of NADPH oxidase. NADPH is an important molecule involved in the respiratory burst, which is a process used by immune cells to kill bacteria and fungi. Defects in the phox genes prevent the production of functional NADPH oxidase, leading to impaired immune function and increased susceptibility to infections.

Pernicious anaemia is an autoimmune condition where the immune system mistakenly attacks the cells in the stomach that produce a protein called intrinsic factor, which is necessary for the absorption of vitamin B12. Antibody-mediated hypersensitivity reactions occur when antibodies bind to specific cells or tissues, leading to their destruction or dysfunction. In the case of pernicious anaemia, autoantibodies are produced that target and destroy the cells producing intrinsic factor, resulting in a deficiency of vitamin B12. Therefore, the correct answer is antibody-mediated.

Autoimmune thrombocytopaenia purpura is an example of an antibody-mediated hypersensitivity reaction. In this condition, the body's immune system mistakenly produces antibodies that target and destroy platelets, leading to a decrease in their numbers. These antibodies bind to the platelets, marking them for destruction by the immune system. This type of hypersensitivity reaction involves the production of antibodies by the immune system, which then mediate the immune response against the body's own cells or tissues.

CD in CD4 stands for cluster of differentiation. This term refers to a group of cell surface molecules that are used to identify and classify different types of immune cells. CD4 specifically refers to a protein found on the surface of helper T cells, which play a crucial role in the immune response by coordinating the actions of other immune cells. By recognizing and binding to specific antigens, CD4 helps activate and regulate the immune system.

In Type II hypersensitivity reactions, cell lysis and inflammation are the pathologic lesions observed. This type of hypersensitivity reaction involves the binding of antibodies to antigens on the surface of cells or tissues, leading to the activation of the complement system and subsequent destruction of the affected cells. This process triggers an inflammatory response, resulting in tissue damage and inflammation.

Serum sickness is the prototype for systemic type III hypersensitivity reactions. It takes a week to manifest as antibodies have to be made.

The principal physiologic function of the cell surface histocompatibility molecules is to bind peptide fragments of foreign proteins for presentation to T cells.

Poststreptococcal glomerulonephritis is an example of an immune complex hypersensitivity reaction. In this condition, immune complexes formed by the interaction of antibodies and antigens (in this case, streptococcal antigens) deposit in the glomeruli of the kidneys, leading to inflammation and damage. This type of hypersensitivity reaction involves the activation of complement and the recruitment of inflammatory cells, resulting in tissue injury.

Dendritic cells are highly specialized antigen-presenting cells that play a crucial role in initiating and regulating immune responses. They are able to take up antigens in peripheral tissues, migrate to lymph nodes, and present the antigens to T cells. This process is essential for the activation of T cells and the initiation of an immune response. Dendritic cells are considered the most effective antigen-presenting cells in the initial stages of the immune response due to their unique ability to efficiently capture and present antigens to T cells. They are able to activate both CD4 and CD8 T cells, leading to the production of specific immune responses against the presented antigens.

All require no previous sensitisation:
Epithelium acts as a barrier
Natural killer cells will kill cells that do not express enough MHC class 1 molecules
The main phagocytes are neutrophils and macrophages
Proteins of the complement system are the main plasma proteins most heavily involved in innate immunity

Necrotising vasculitis and inflammation are the pathologic lesions seen in Type III hypersensitivity reactions. In this type of reaction, immune complexes formed by the binding of antibodies to antigens are deposited in various tissues, leading to an inflammatory response. The immune complexes can activate complement and attract neutrophils, causing tissue damage and inflammation. This type of hypersensitivity reaction is associated with diseases such as systemic lupus erythematosus and rheumatoid arthritis.

They can act in all 3 ways.

Perivascular cellular infiltrates, edema, cell destruction, and granuloma formation are characteristic pathological lesions seen in Type IV hypersensitivity reactions. Type IV hypersensitivity reactions, also known as delayed-type hypersensitivity reactions, are mediated by T cells and occur 24-72 hours after exposure to an antigen. These reactions are typically associated with chronic inflammation and tissue damage. Examples of Type IV hypersensitivity reactions include contact dermatitis, tuberculin reaction, and granulomatous diseases such as sarcoidosis.

Atopy refers to the predisposition to develop localized immediate hypersensitivity reactions to a variety of inhaled and ingested allergens. This means that individuals with atopy are more likely to have allergic reactions when exposed to certain substances, such as pollen, dust mites, or certain foods. These reactions can manifest as symptoms like sneezing, itching, and difficulty breathing. Atopy is thought to have a genetic component and can be influenced by environmental factors.

T lymphocytes mediate cellular immunity. This type of immunity involves the direct action of T cells, which are a type of white blood cell, in recognizing and destroying infected or abnormal cells in the body. T lymphocytes play a crucial role in the immune response by coordinating and regulating the actions of other immune cells. They are able to recognize specific antigens and activate immune responses to eliminate pathogens or abnormal cells. Cellular immunity is important for defense against intracellular pathogens, such as viruses and certain bacteria, as well as for surveillance and elimination of cancer cells.

Usually sporadic
Phenotypically normal; some may have respiratory infections and diarrhoea, or is expressed if there is a second immunodeficiency.
Risk of anti-IgA sensitisation and anaphylactoid reactions following exposure to IgA containing blood products

Acute rheumatic fever is an example of an antibody-mediated hypersensitivity reaction. In this type of reaction, antibodies produced by the immune system mistakenly target and attack healthy tissues in the body. In the case of acute rheumatic fever, antibodies produced in response to a streptococcal infection cross-react with proteins in the heart, joints, and other tissues, causing inflammation and damage. This immune response is mediated by antibodies, specifically IgG and IgM, which bind to the target tissues and trigger an inflammatory response.

Type 1 diabetes mellitus is an example of a T-cell mediated hypersensitivity reaction. In this condition, the immune system mistakenly attacks and destroys the insulin-producing cells in the pancreas. This destruction is primarily mediated by T-cells, which are a type of white blood cell involved in the immune response. The T-cells recognize the pancreatic cells as foreign or abnormal and initiate an immune response against them. This leads to a deficiency of insulin and the development of type 1 diabetes mellitus.

Multiple sclerosis is an autoimmune disease characterized by the destruction of myelin, the protective covering of nerve fibers in the central nervous system. This destruction is caused by an abnormal immune response where T-cells, a type of white blood cell, mistakenly attack the myelin. Therefore, multiple sclerosis is an example of a T-cell mediated hypersensitivity reaction.

Because CD40 interactions are involved in change of IgM production to IgG production.

NK cells are CD3 negative. CD40 is the molecule that CD4+ T cells use to assist in B cell responses.

Neoplastic predisposition is not one of the categories of diseases that show association with the HLA locus. The HLA locus is primarily associated with the immune system and plays a role in autoimmune disorders, inflammatory diseases, and inherited errors of metabolism. Neoplastic predisposition refers to an increased risk of developing cancer due to genetic factors unrelated to the HLA locus.

IL-1, IL-6 and TNF are cytokines that mainly mediate INNATE immunity.

Interferons protect against viral infections.
IL-1 and TNF promote leukocyte recruitment and acute inflammatory responses.

The three viral enzymes contained in the HIV virion are Integrase, Protease, and Reverse transcriptase. Integrase is responsible for integrating the viral DNA into the host cell's DNA. Protease plays a crucial role in the maturation of the virus by cleaving the viral polyprotein into individual functional proteins. Reverse transcriptase is involved in the replication process of the virus, converting the viral RNA into DNA. These enzymes are essential for the replication and survival of the HIV virus within the host.

AKA Bruton’s agammaglobulinaemia
Absence of gammaglobulins in blood
Failure to mature beyond pre-B cell stage in the bone marrow
Mutations or deletions in gene encoding enzyme tyrosine kinase (Btk)
Low or undectable Ig, reduced or absent B cells in lymphoid tissues, no germinal centres in lymph nodes
T cells maturation, numbers and functions: normal
Autoimmunity in 20%
Monthly IvIg reduces infectious complications

The Gram Negative LPS/LBP complex facilitates LPS binding to CD14. CD14 is a glycoprotein found on the surface of various immune cells, including macrophages and dendritic cells. It acts as a receptor for lipopolysaccharide (LPS), a component of the outer membrane of Gram-negative bacteria. The LPS/LBP complex helps to deliver LPS to CD14, initiating an immune response and triggering the release of pro-inflammatory cytokines.