Immunity: Antigens and Types of Immune Responses

Overview of Immunity

• The immune system protects against microorganisms by attacking foreign antigens and pathogens, thus preventing infections.
• Homeostasis is maintained as damaged cellular substances are digested and removed.
• The immune system identifies and destroys mutated cells to prevent malignancies.

Definition of Antigens

• An antigen is a substance, often a protein but also polysaccharides, lipoproteins, or nucleic acids, that triggers an immune response.
• The immune system distinguishes between 'self' antigens (body's own molecules) and 'non-self' antigens, tolerating the former and vigorously responding to the latter.

Types of Immunity

Innate Immunity

• Innate immunity is present at birth, offering a first-line defense against pathogens through a nonspecific response.
• It uses white blood cells like neutrophils and monocytes, which respond quickly without prior exposure.
• The response is rapid, occurring within minutes, crucial for immediate defense.

Acquired Immunity

• Acquired immunity develops after exposure to foreign substances, resulting in active or passive immunity.
• Active acquired immunity occurs when the body's own immune response to pathogens leads to the production of antibodies and memory cells.
• Passive acquired immunity involves the transfer of antibodies from one individual to another, giving immediate but short-lived protection.

Lymphoid System and Immune Cells

Structure of the Lymphoid System

• Central lymphoid organs, which include the thymus gland and bone marrow, produce and mature lymphocytes.
• Peripheral lymphoid organs, such as lymph nodes, spleen, tonsils, and mucosal-associated lymphoid tissues, filter antigens and circulate lymphocytes.
• The thymus is essential for T lymphocyte maturation, largest during childhood, and gradually replaced by fat after puberty.

Role of Lymphocytes

• B lymphocytes differentiate into plasma cells that produce antibodies, essential for humoral immunity.
• T lymphocytes, including T cytotoxic and T helper cells, are responsible for cell-mediated immunity and regulating immune responses.
• Memory cells, some activated T and B cells, provide long-term immunity upon re-exposure to antigens.

Immunoglobulins and Their Functions

• IgG is responsible for secondary immune responses and is the only immunoglobulin that crosses the placenta.
• IgA protects mucous membranes and lines body surfaces.
• IgM is responsible for primary immune responses and forms antibodies to ABO blood antigens.
• IgD aids in B lymphocyte differentiation and is present on the lymphocyte surface.
• IgE is involved in allergic reactions and fixes to mast cells and basophils.

Cell-Mediated Immunity

• CD8 (cytotoxic T cells) directly attack foreign pathogens and release cytolytic substances, participating in specific immune responses.
• CD4 (helper T cells) regulate humoral and cell-mediated immunity, differentiating into TH1 and TH2 subsets that produce distinct cytokines.
• Memory T cells remain after an infection, enhancing the speed and intensity of the immune response upon re-exposure.
• Natural killer (NK) cells are large lymphocytes that mediate immunity without prior sensitization.
• NK cells target and destroy infected or cancerous cells, contributing to the innate immune response.
• NK cells are distinct that T and B cells and have granules in their cytoplasm containing cytotoxic substances.
• NK cells are key in eliminating virus-infected cells, tumor cells, and transplanted grafts.
• NK cells do not require prior sensitization, allowing for immediate immune response and immune surveillance.
• Dendritic cells activate T cells and start the immune response.
• Found in tissues like skin (Langerhans cells) and mucosal surfaces, dendritic cells are crucial for antigen presentation due to their dendritic processes.
• Immature dendritic cells circulate in the blood and mature by capturing antigens and transporting them to T cells.

Immune Responses Overview

Primary vs. Secondary Immune Response

• The secondary immune response is faster (1 to 3 days), stronger, and longer-lasting than the primary response.
• Memory cells are crucial for rapid antibody production upon re-exposure, creating immunological memory.
• IgG is the dominant antibody in secondary responses, crosses the placental barrier, and protects newborns for at least 3 months.
• Infants receive passive immunity through IgA in breast milk and colostrum, which protects against infections early in life.

Cell-Mediated Immunity

• Cell-mediated immunity involves T cells, macrophages, and NK cells, recognizing specific antigens.
• It combats pathogens within host cells, like viruses and certain bacteria (e.g., mycobacteria).
• It has a role in fungal infections, transplant rejection, contact hypersensitivity reactions, and tumor immunity.

Immunosenescence and Aging

• Immunosenescence, a decline in immune function with age, increases susceptibility to infections and cancers in older adults.
• Aging decreases immunoglobulin levels, suppressing humoral immune response.
• The thymus shrinks with age, reducing T cell production and function, which is a primary cause of immunosenescence.
• Older adults show deficiencies in T and B cell activation, cell cycle transit time, and differentiation, leading to an accumulation of memory cells.
• The antibody response to vaccinations is lower in older adults compared to younger individuals.
• A key indicator of immunosenescence is the increased incidence of cancer in older adults, due to a less effective immune system.
• Older adults are more susceptible to infections like influenza and pneumonia that they previously fought effectively.
• Bacterial pneumonia is a leading cause of death from infections in older adults.

Hypersensitivity Reactions

Overview of Hypersensitivity

• Hypersensitivity reactions happen when the immune system overreacts to foreign antigens or mistakenly targets self-tissues, causing tissue damage.
• Autoimmune diseases are a form of hypersensitivity where the body attacks self-antigens.
• Hypersensitivity reactions are classified by antigen source, time sequence (immediate or delayed), or immunologic mechanisms.
• The types of hypersensitivity reactions include Type I (IgE-mediated), Type II, Type III (immediate), and Type IV (delayed).

Type I Hypersensitivity: IgE-Mediated Reactions

• Type I reactions involve IgE antibodies and anaphylactic responses in sensitized individuals and the release of chemical mediators from mast cells and basophils.
• Anaphylaxis, a life-threatening manifestation, requires immediate medical intervention to prevent severe outcomes.

Mechanism of Type I Reactions

• Upon first exposure to an allergen, IgE antibodies are generated binding to mast cells and basophils, sensitizing the individual.
• Subsequent exposures to the same allergen trigger degranulation, releasing mediators like histamine, causing allergic symptoms such as smooth muscle contraction, increased vascular permeability, and mucus secretion.

Clinical Examples and Management

• Anaphylaxis is a severe, systemic reaction occurring within minutes of allergen exposure, with symptoms like hypotension, dyspnea, and rapid pulse.
• Common allergens causing anaphylaxis are drugs, insect stings, and foods, but drugs are the leading cause of anaphylaxis-related deaths.
• Allergic rhinitis (hay fever) is a common type I hypersensitivity reaction triggered by airborne allergens, causing sneezing and nasal discharge.

Overview of Allergic Reactions

Symptoms of Allergic Reactions

• Common symptoms include nasal discharge, sneezing, tearing, mucosal swelling, airway obstruction, and itching of the eyes, nose, throat, and mouth.
• Asthma patients exhibit an allergic component often with a history of atopic disorders like infantile eczema and food intolerances.
• Inflammatory mediators cause bronchial smooth muscle constriction and excess mucus secretion, resulting in dyspnea, wheezing, and coughing.

Types of Allergic Reactions

• Allergic reactions are classified into four types based on the immune response: Type I (Immediate), Type II (Cytotoxic), Type III (Immune-Complex), and Type IV (Delayed).
• Each type shows distinct mechanisms and clinical manifestations, with Type I being the most common and Type IV involving cell-mediated immunity, all of which are crucial in diagnosing and treating allergic conditions.

Type I: Immediate Hypersensitivity

• Characterized by rapid onset of symptoms upon exposure to allergens, mediated by IgE antibodies.
• Common examples include allergic rhinitis, asthma, and anaphylaxis.
• Treatment often involves antihistamines, corticosteroids, and allergen avoidance.

Type II: Cytotoxic and Cytolytic Reactions

• IgG or IgM antibodies bind to antigens on cell surfaces, leading to cell destruction.
• Common disorders include hemolytic transfusion reactions and autoimmune diseases like Goodpasture syndrome.
• The complement system mediates tissue damage, resulting in rapid clinical manifestations.

Type III: Immune-Complex Reactions

• Antigen-antibody complexes deposit in tissues, leading to inflammation and tissue damage.
• This is associated with autoimmune disorders, such as systemic lupus erythematosus (SLE) and rheumatoid arthritis.
• Clinical manifestations are in various organs like the kidneys and skin, depending on the location of the deposits.

Type IV: Delayed Hypersensitivity Reactions

• Sensitized T cells participate in a cell-mediated immune response that takes 24 to 48 hours to develop.
• Examples include contact dermatitis and transplant rejection.
• Common antigens include metals, rubber compounds, and plant allergens like poison ivy.

Case Studies and Examples

• Allergic rhinitis is often a precursor to asthma with many patients experiencing they both experience this situation..
• Treatment strategies for allergic rhinitis improve their asthma.

Overview of Delayed Hypersensitivity Reactions

• Delayed hypersensitivity reactions are mediated by T cells and cause tissue damage.
• Sensitized T cells release cytokines that attract macrophages to the site of antigen exposure, resulting in tissue destruction that takes 24 to 48 hours to develop.
• Key cytokines like TNF-alpha and IFN-gamma active macrophages and cause inflammation.
• Antibodies are absent in type IV reactions.

Examples of Delayed Hypersensitivity Reactions

• Contact dermatitis occurs by a skin-penetrating substance that binds to proteins and becomes antigenic.
• Other examples include hypersensitivity reactions to bacterial, fungal, or viral infections and transplant rejection.
• Drug sensitivity reactions can also cause skin symptoms.
• Immune response to the tubercle bacillus, leading to tuberculosis, is the classic example of microbial hypersensitivity.
• The purified protein derivative (PPD) test is a practical application of delayed hypersensitivity, used to diagnose tuberculosis.

Contact Dermatitis

Allergic Contact Dermatitis

• Allergic contact dermatitis occurs when skin is exposed to allergens, leading to sensitization and reactions.
• Common allergens include nickel, rubber compounds, poison ivy, and cosmetics.
• Eczematous lesions appear within 48 hours on re-exposure, typically develops in 7 to 14 days after initial allergen exposure.
• Symptoms include redness, swelling, itching, and the formation of papules and vesicles.
• Chronic contact that is dermatitis is localized to the area of exposure and can resemble atopic dermatitis.

Acute vs. Chronic Contact Dermatitis

• Acute contact dermatitis has red, swollen lesions that are itchy and may burn or sting while chronic contact dermatitis leads to thickened, scaly, and lichenified skin.
• Contact dermatitis that is localized as a opposed to to atopic dermatitis.
• Management includes avoiding allergens and using topical corticosteroids.

Allergy Assessment and Diagnosis

Comprehensive Allergy History

• Identifying allergens and at-risk individuals requires a thorough patient history.
• Genetic predisposition to allergies can be indicated by a family history of atopic reactions.
• Identifying the timing and that nature of allergic reactions helps identify seasonal or environmental triggers as well as social, environmental factors need to be assessed.
• Discovering food allergies involved keeping track.

Diagnostic Techniques

• Immunologic techniques assess lymphocyte, eosinophil, and that immunoglobulin abnormalities.
• Identifying the lymphocyte counts by testing a complete blood count provides to be immunodeficient.
• Elevated eosinophil counts and serum IgE levels are indicative of type I hypersensitivity reactions.
• Skin testing may be use but also blood test.
• Identifying potential trigger foods one at a time after symptoms stop.

Skin Testing for Allergies

Methods of Skin Testing

• Can be performed using scratch that is intradermal, or patch tests to identify one or more specific allergens.
• Injecting an allergen under the skin that is causing the test by a skin pricking.
• Applying allergens covered using a skin that is worn for 48 to 72 hours.
• Test results can be altered and have control sites to compare the skin to the body.

Interpreting Skin Test Results

• Reactions in scratch that is intradermal tests occur within 5 to 10 minutes, while patch tests require longer observation.
• A positive reaction indicates sensitization but does not correlate with the severity of symptoms.
• Comparing the test result with patient history is important because false positives and false negatives can occur.
• Allergy disorders cant be ruled of and sensitization does not mean certain causation if its positive.

Understanding Allergic Reactions

Mechanisms of Allergic Reactions

• The immune system overreacting to an allergen is the cause.
• Being tested positive in skin does not confirm symptoms are truly caused by the test result.
• Results can be assessed with correlation between skin test results and patient history .

Anaphylaxis: A Life-Threatening Reaction

• Anaphylaxis can be triggered suddenly after exposure to allergens, particularly from drugs or insect stings.
• Quickly assessing symptoms, maintaining airway, and using life saving drugs and shock treatment.
• Anaphylaxis is commonly treated using epinephrine, which is administered parenterally.

Chronic Allergic Reactions

• Most allergic reactions are chronic, with periods of exacerbation and remission.
• Treatment focuses on allergen identification, symptom relief, and potential desensitization through immunotherapy.
• Environmental management symptoms can be managed.

Interprofessional and Nursing Management

Patient Education and Lifestyle Adjustments

• Educate patients that are reducing allergen exposure with symptom recognition.
• Encourage stress management techniques, as stress can exacerbate allergic reactions.
• Medic Alert bracelets are recommended.

Emergency Preparedness for Anaphylaxis

• The correct dose and method on how to use injectable epinephrine is crucial.
• Patients can carry kits for out door allergic reactions.
• In case of any allergic trigger make sure to call for symptoms.

Drug Therapy for Allergic Disorders

Antihistamines and Their Role

• Antihistamines are effective for allergic rhinitis, itching, and hives but not for severe reactions.
• By blocking H1 receptors, antihistamines can relieve symptoms.
• At the start of symptoms using medications achieve best results.

Corticosteroids and Other Medications

• Nasal corticosteroids are prescribed for allergic rhinitis as some patients or some severe episodes taking an oral route is prescribed.
• Topical itch medications help.
• Allergie release mast cell stabilizers like Cromolyn by inhibiting histamine release .

Immunotherapy and Long-Term Management

Overview of Immunotherapy

• Patients may be be required to get immunotherapy patients with constant allergic events and if drug therapy does not help.
• To achieve hyposensitivity, increasing doses of allergen extracts is injected.
• Food allergies as well as eczema are conditions in which allergies don't respond.

Importance of Ongoing Management

• Educating yourself with allergies will help long term patient comfort.
• Follow ups help discover symptom triggers and help to improve symptoms.
• Tracking triggers and responses to treatment will help patients.

Immunotherapy Overview

Definition and Indications

• Immunotherapy makes patients with anaphylactic reactions to insect venom, have reduced sensitivity to allergens.
• By desensitizing small doses of allergens the reaction will be less serve when one get exposed.
• Total desensitization is not entirely impossible, with that always avoid.

Mechanism of Action

• Immunotherapy involves allergen specific T suppressor cells that develop in patients undergoing immunotherapy which contributes to the immune response.
• IgE is triggered and histamine release is expressed upon exposure to an allergen in atopic people with IgE levels are elevated.
• To reduce antigen binding and reduce cell degranulation, immunotherapy increases IgG levels and is its goal.

Methods of Administration

• Subcutaneous Immunotherapy (SCIT): Injections for years starting at small doses.
• Sublingual Immunotherapy (SLIT): Doses can be delivered at home.

Risks and Management

• Having emergency equipment present during administering immunotherapy equipment is crucial because anaphylactic events may happen.
• Early systemic reactions, such as itching, hives, and hypotension are signs for medical attention.
• Managing reactions involves keeping a careful record.

Latex Allergies

Overview of Latex Allergies

• Healthcare settings can lead to latex allergies.
• Various latex products causes allergic symptoms but prolonged contact causes reactions.

Types of Latex Allergies

• Skin dryness and being itchy 6-48 is identified as a Type IV Allergic Contact Dermatitis.
• Anaphylaxis with Latex Type I Allergic Reactions, can be expressed by just skin irritations.

Latex-Food Syndrome

• Latex-food syndrome occurs when people with latex express similar proteins and react.
• Foods that that express such are common foods.

Nursing Management for Latex Allergies

• Knowing of high allergies and making sure products are latex free will help lower allergy events.
• Patient's overall medical records will help to manage risk factors.

Multiple Chemical Sensitivity (MCS)

Overview of MCS

• Multiple Chemical Sensitivity is triggered through chemicals, biologic and even physically, that are vague is nature and are at low levels.
• Common triggers will synthetic material usage.
• Women aged 30 to 50 are most common to have this event of sensitity

Symptoms and Diagnosis

• A vast symptom in the body such as fatigue and dizziness occurs in body.
• gastrointestinal disturbances with cognitive difficulties, and mood changes, that are is subjective is possible.
• Diagnosing is made upon just patient history itself.

Treatment and Management

• Avoiding chemical usages to make sure the symptom has less triggers.
• Using coping skills and stress management techniques with psychotherapy will help.
• Managing stress is important.

Autoimmunity

Understanding Autoimmunity

• When one's body immune is attacking its own cells because it is not able to differentiate.
• Is an individual is condition can be expressed from tissue damage.
• Genes can cause autoimmune diseases when the body.

Factors Contributing to Autoimmunity

• Age is a part of this occurrence with increases after 50 years of age.
• HLA is a marker for individuals genes and correlated with specific conditions of autoimmune events.
• Changing of ones body cell can trigger an event.

Examples of Autoimmune Diseases

• Autoimmune diseases cluster within families; e.g., rheumatoid arthritis and Addison's disease.
• When viral infections like type 1 diabetes can trigger an autoimmune attack.
• Infections caused by streptococcus can lead to rheumatic fever and rheumatic heart disease, where antibodies mistakenly attack heart tissues.

Gender and Hormonal Influences

• Women's hormonal influence also can cause autoimmune diseases.
• Certain hormonal influences can make the women become or improve during pregnancy.

Explore the basics of immunity, including how the immune system defends against pathogens and maintains homeostasis. Learn about antigens, the substances that trigger immune responses. Understand the differences between innate and adaptive immunity, and their roles in protecting the body.