immunology test 1

Innate Immunity

A non-specific, rapid immune response that acts as the first line of defense using barriers, phagocytes, and inflammatory mediators.

Components of Innate Immunity

Includes anatomical barriers (skin, mucosa), chemical barriers (pH, enzymes), cellular elements (macrophages, neutrophils, NK cells), and soluble factors (complement, cytokines).

Physical Barriers

Epithelial cells, tight junctions, mucus, and cilia help prevent entry of pathogens.

Chemical Barriers

Includes lysozyme, defensins, lactoferrin, and the acidic pH in the stomach.

Lysozyme

An enzyme found in secretions and macrophages that hydrolyzes peptidoglycan in bacterial cell walls.

Lactoferrin

Binds iron to inhibit bacterial growth; found in milk, saliva, and tears.

Interferons (IFNs)

Cytokines released in response to viruses that inhibit viral replication and activate immune cells.

Phagocytosis

Process by which neutrophils and macrophages engulf and destroy pathogens.

Natural Killer (NK) Cells

Kill virus-infected and tumor cells without prior sensitization.

Complement System

Cascade of proteins that enhances phagocytosis, inflammation, and cell lysis.

Inflammation

A localized response to infection or injury characterized by redness, heat, swelling, and pain.

Neutrophils

First responders to infection, phagocytize pathogens, and release antimicrobial compounds.

Macrophages

Phagocytic cells derived from monocytes, produce cytokines, and present antigens.

Eosinophils

Combat parasites and are involved in allergic responses.

Basophils

Release histamine during allergic reactions.

Dendritic Cells

Bridge innate and adaptive immunity by processing and presenting antigens.

Pattern Recognition Receptors (PRRs)

Receptors like TLRs that detect PAMPs on pathogens.

Toll-like Receptors (TLRs)

A type of PRR that recognizes specific microbial components.

Acute Phase Proteins

Proteins like CRP and serum amyloid A, produced by the liver in response to inflammation.

Cytokines in Innate Immunity

Include IL-1, IL-6, TNF-alpha which mediate inflammation and fever.

Acquired Immunity

Specific immunity developed after exposure to antigens, involving memory and specificity.

B Cells

Lymphocytes that produce antibodies against specific antigens.

T Cells

Lymphocytes that recognize antigen-MHC complexes and orchestrate the immune response.

Humoral Immunity

Immunity mediated by antibodies produced by B cells.

Cellular Immunity

Immunity mediated by T cells which target infected or abnormal cells.

Primary Immune Response

Occurs after first exposure to antigen, slower with lower antibody levels.

Secondary Immune Response

Faster and stronger response due to memory cells.

Antigen

A molecule that elicits an immune response.

Antigen Presenting Cells (APCs)

Cells like dendritic cells and macrophages that present antigens via MHC to T cells.

Clonal Selection

Activation and proliferation of lymphocytes specific to an antigen.

Memory Cells

Long-lived B or T cells that respond rapidly upon re-exposure to the antigen.

Immunologic Specificity

Ability of the immune system to target specific pathogens.

Immunologic Memory

Retention of antigen-specific lymphocytes after an immune response.

T Helper Cells (CD4+)

Stimulate B cells and cytotoxic T cells; orchestrate the immune response.

Cytotoxic T Cells (CD8+)

Kill infected or abnormal cells by recognizing antigen on MHC I.

MHC Class I

Presents endogenous antigens to CD8+ T cells.

MHC Class II

Presents exogenous antigens to CD4+ T cells.

T Cell Receptor (TCR)

Recognizes antigens presented by MHC molecules.

Co-stimulation

Required second signal for full activation of T cells (e.g., CD28-B7 interaction).

Helper T Cell Subtypes

Th1 promotes cellular immunity, Th2 promotes humoral immunity.

Cytokines

Small proteins released by cells that affect the behavior of other cells, key in immune signaling.

Chemokines

A subset of cytokines that direct the movement of immune cells.

IL-1

Pro-inflammatory cytokine involved in fever and activation of immune cells.

IL-2

Stimulates proliferation of T cells.

IL-4

Promotes B cell class switching to IgE and differentiation of Th2 cells.

IL-5

Stimulates eosinophil growth and activation.

IL-6

Induces acute phase response and B cell differentiation.

IL-10

Anti-inflammatory cytokine, inhibits Th1 responses.

IL-12

Promotes Th1 differentiation and IFN-gamma production.

TNF-alpha

Pro-inflammatory cytokine, causes fever, inflammation, and can induce apoptosis.

Interferon-gamma

Activates macrophages and enhances antigen presentation.

Chemotaxis

Movement of immune cells in response to chemokine gradients.

CXCL8 (IL-8)

Attracts neutrophils to sites of infection.

Adhesion Molecules

Help leukocytes adhere to endothelium and migrate to infection sites.

Selectins

Mediate initial attachment of leukocytes to endothelial cells.

Integrins

Strengthen adhesion of leukocytes to endothelium.

ICAM-1

Ligand for LFA-1 integrin on leukocytes, helps in firm adhesion.

Role of Cytokines

Coordinate immune responses by promoting cell growth, differentiation, or suppression.

Cytokine Storm

Excessive cytokine release that can lead to tissue damage and multi-organ failure.

Monokines

Cytokines produced by monocytes

Autoimmunity

Immune response against self-antigens leading to tissue damage.

Central Tolerance

Elimination of self-reactive lymphocytes during development.

Peripheral Tolerance

Mechanisms outside primary lymphoid organs to prevent autoimmunity (e.g., Tregs, anergy).

AIRE Gene

Enables expression of self-antigens in the thymus for negative selection.

T Regulatory Cells (Tregs)

Suppress autoreactive immune cells and maintain tolerance.

Molecular Mimicry

Pathogens share epitopes with self-antigens, leading to cross-reactivity.

Autoantibodies

Antibodies that target host tissues.

Systemic Lupus Erythematosus (SLE)

Autoimmune disease involving anti-nuclear antibodies.

Rheumatoid Arthritis

Autoimmune inflammation of joints with production of rheumatoid factor.

Type 1 Diabetes

Autoimmune destruction of pancreatic beta cells.

Hashimoto Thyroiditis

Autoimmune attack on thyroid gland causing hypothyroidism.

Multiple Sclerosis

Autoimmune attack on myelin in CNS.

Goodpasture Syndrome

Autoantibodies target basement membrane in lungs and kidneys.

Pemphigus Vulgaris

Autoantibodies against desmoglein in skin, causing blistering.

Autoimmune Hemolytic Anemia

Autoantibodies cause destruction of red blood cells.

Graves Disease

Autoantibodies stimulate TSH receptor, causing hyperthyroidism.

Myasthenia Gravis

Autoantibodies block acetylcholine receptors at neuromuscular junction.

Antinuclear Antibodies (ANA)

Diagnostic marker for systemic autoimmune diseases.

Treatment of Autoimmunity

Includes immunosuppressants, corticosteroids, biologics (e.g., anti-TNF).

Genetic Predisposition

Certain HLA alleles (e.g., HLA-DR3, HLA-DR4) are associated with autoimmune diseases.

Hypersensitivity Reactions

Excessive immune responses that cause tissue damage.

Type I Hypersensitivity

Immediate allergic reaction involving IgE and mast cells (e.g., asthma, anaphylaxis).

Type II Hypersensitivity

Antibody-mediated cytotoxic reaction (e.g., hemolytic anemia, Goodpasture).

Type III Hypersensitivity

Immune complex-mediated reaction (e.g., SLE, serum sickness).

Type IV Hypersensitivity

Delayed T-cell mediated reaction (e.g., contact dermatitis, TB test).

Mast Cells

Release histamine and other mediators in Type I reactions.

Anaphylaxis

Severe, systemic allergic reaction, requires immediate epinephrine treatment.

Allergen

Substance that triggers IgE-mediated hypersensitivity.

Sensitization

First exposure to allergen leading to IgE production.

Degranulation

Release of histamine, prostaglandins, and leukotrienes from mast cells.

Arthus Reaction

Local Type III hypersensitivity reaction due to immune complex deposition.

Serum Sickness

Systemic Type III reaction from foreign protein exposure.

Delayed-Type Hypersensitivity (DTH)

Type IV reaction involving memory Th1 cells (e.g., TB skin test).

Contact Dermatitis

Type IV reaction from allergens like nickel or poison ivy.

DRESS Syndrome

Severe drug-induced hypersensitivity involving Type IVb reaction.

Autoimmune Cytopenia

Type II hypersensitivity causing low blood cell counts.

Hemolytic Disease of Newborn

Type II reaction due to Rh incompatibility.

Myasthenia Gravis (revisited)

Type II reaction against acetylcholine receptors.

Patch Testing

Diagnostic method for contact hypersensitivity.

Biologics for Allergy

Anti-IgE (omalizumab), anti-IL4, anti-IL5 for severe allergic conditions.