Ch 14 microbiology 211 PDF

Preview

Summary

Download Ch 14 microbiology 211 PDF

Description

Chapter 14: Disorders in Immunity

The Immune Response: A Two-Sided Coin •

The human immune system is powerful and intricate, having the potential to cause injury and disease.

•

Immunopathology: ________________________________________

•

Hypersensitivity: over reaction of the immune system -

•

Allergy and autoimmunity

Hyposensitivity or immunodeficiency: immune system is incompletely developed, suppressed, or destroyed

Type I Allergic Reactions: Atopy and Anaphylaxis •

Allergy: exaggerated immune response that is manifested by inflammation -

Caused by physiological effects of mast cell derived allergic

•

Allergens: _______________________________________________

•

2 Levels of Severity -

__________: chronic local allergy such as hay fever or asthma

-

________________: systemic, sometimes fatal reaction that involves airway obstruction and circulatory collapse

Who Is Affected? •

Nearly half of the US population is affected by airborne allergens

•

Majority are mild; some are severe

•

May last a lifetime, some are “outgrown,” and others develop later in life

•

Generalized susceptibility is inherited

•

Why are they so common?

– Hygiene Hypothesis: ___________________________________ Mechanisms of Type I Allergy: Sensitization and Provocation (Fig 14.4) •

The Role of Mast Cells and Basophils: -

Mast cells are located in all all connective tissue in particularly high concentrations in the lungs, skin, gastrointestinal tract, and genitourinary tract.

-

Each cell carries 30,000 to 100,000 cell receptors that bind IgE and degranulate, releasing inflammatory cytokines.

•

Symptoms of allergy are not caused by the direct action of allergen on tissues, but the physiological effects of mast-cell-derived allergic mediators on target organs.

•

They are a type of WBCS AND basophils circulate more in the blood.

Cytokines, Target Organs, and Allergic Symptoms •

•

Histamine: -

Most profuse and fast-acting allergic mediator

-

Effect on small bronchi and intestine: constriction

-

Effect on skin: wheal and flare reactions in the sking

Bradykinin: -

Prolonged contraction of the bronchioles

-

Dilation of peripheral arterioles

-

decreased capillary permeability

-

Increased mucus secretion

•

Serotonin: effects appear to complement histamine and bradykinin

•

Prostaglandins: -

Vasodilation

-

Increased vascular permeability

-

Increased sensitivity to pain

-

Bronchoconstriction

-

•

NSAIDs prevent the actions of prostaglandins.

Leukotriene: -

Induces gradual contraction of smooth muscle

-

Slow reacting substance of anaphylaxis”

-

Prolonged bronchospasm

-

Increased vascular permeability

-

Increases mucus secretion

IgE- and Mast-Cell-Mediated Allergic Conditions: Atopic Diseases •

Hay fever: A generic term for allergic rhinitis -

•

•

•

Seasonal or year-round reaction to inhaled plant pollen, molds, or inhalants

Asthma: -

Airways of asthmatics are extremely sensitive to minute amounts of allergens and are chronically inflamed and constricted.

-

Symptoms range from labored breathing to fatal suffocation

Atopic dermatitis/eczema: -

Intensely itchy inflammatory condition of the skin

-

Sensitization occurs through ingestion inhalation and skin contact with allergens.

-

Usually begins in infancy and is characterized by reddened, weeping, encrusted skin lesions on the face, scalp, neck, and inner surfaces of limbs and trunk

-

Progresses to a dry, scaly, thickened skin condition in adults

Drug Allergy -

Reactions range from a mild rash to fatal anaphylaxis.

•

Allergen is not the intact drug itself, but a happen given off when the liver processes the drug.

Food Allergy (can rarely be anaphylactic) -

Most common food allergens are peanuts, fish, cow’s milk, eggs, shellfish, and soybeans.

-

Symptoms include vomiting, diarrhea, and abdominal pain.

-

Other manifestations include hives, rhinitis, asthma and occasionally anaphylaxis

Anaphylaxis: An Overpowering IgE-Mediated Allergic Reaction •

Anaphylaxis/anaphylactic shock: -

Systemic anaphylaxis: characterized by sudden respiratory and circulatory disruption that can be fatal within minutes due to the airway blockage

-

Bee stings and injection of antibiotics or serum are most commonly implicated

-

Results of the sudden and massive release of chemicals into the tissues and blood which act rapidly on target organs

Treatment and Prevention of Allergy fig 14.9 pg 416 1. Avoid the allergen 2. Take drugs to block the allergy -

Corticosteroids, cromolyn, antihistamines, epinephrine, asprin/acetaminophen ( pain relief)

-

Whipworms •

Trichuris suis: re directs Ig- e and eosinophils to react to it instead of the allergy.

3. Desensitization: -

What’s in an allergy shot?

-

How do the shots work? -

Blocking antibody:

-

Also hypothesized that allergen delivered in this fashion combines with IgE itself, taking it out of circulation

-

Eating small amounts of food allergens may accomplish desensitization

-

Whipworms (insert explanation)

Type II Hypersensitivities: Reactions That Lyse Foreign Cells •

A complex group of syndromes that involve complement-assisted destruction (lysis) of cells by antibodies (IgG and IgM) directed against those cells’ surface antigens: -

Transfusion reactions: Agglutination

-

Hemolytic disease of the newborn (See Figure 14.8) -

Rh factor

Type III Hypersensitivities: Immune Complex Reactions •

Involves the binding of soluble antigen with antibody

•

In immune complex disease, these complexes are deposited in the basement membrane of epithelial tissues: -

•

Neutrophils release lysosomal granules that cause a destructive inflammatory condition.

Arthus reaction and serum sickness are examples (Figure 14.9)

Type IV Hypersensitivities: Cell-Mediated (Delayed) Reactions •

Results when T cells respond to antigens displayed on self-tissues or transplanted foreign cells

•

Traditionally known as “delayed hypersensitivity”: -

•

it take one to several days signs/symptoms to develop

Tuberculin reaction: -

Acute skin inflammation at the injection site following an extract of Mycobacterium tuberculosis.

•

-

Similar skin reactions occur with leprosy, syphilis, histoplasmosis, toxoplasmosis, and candidiasis.

-

TH1 cells release cytokines and recruit macrophages, neutrophils and eosinophils to the site, causing a red bump.

Contact Dermatitis -

List at least 3 allergens that cause contact dermatitis: Resins in poison ivy and poison oak,

-

haptens in household and personal articles

-

haptens in drus

-

Requires a sensitizing dose followed by a provocative dose.

-

Allergen penetrates the outer skin layers: -

Processed by skin dendritic cells and presented to T cells

-

Subsequent exposures attract lymphocytes and macrophages.

-

Cells release enzymes and cytokines that damage the epidermis and vicinity.

An Inappropriate Response to Self: Autoimmunity •

Possible Causes -

Genetics

-

Molecular mimicry:

-

Infection -

-

•

Some autoimmune disorders are possibly triggered by viral infection

Gut Microbiome - Composition has changed drastically in recent years - May be future tool for treatment

Autoimmune diseases: individuals develop hypersensitivity to themselves -

Auto-antibodies, T cells or bot:

•

•

•

•

•

the abnormal attack against self-antigens

May be systemic or organ specific

Systemic lupus erythematosus (SLE or lupus): -

Manifestations vary, but all patients develop autoantibodies against organs, tissues, or intracellular materials.

-

Viral infection and loss of normal immune response suppression are suspected as causes.

Rheumatoid arthritis: -

Causes progressive, debilitating damage, primarily to the joints and and at times to the lungs, eyes, skin, and nervous system

-

Autoantibodies form immune complexes that bind to the synovial membrane of joints

-

Chronic inflammation develops, leading to scar tissue and joint destruction.

-

Epstein-Barr virus has been implicated as a precipitating cause.

Graves’ disease: Hyper-thyroidsism -

Attachment of autoantibodies to receptors on thyroxin-secreting follicle cells of the thyroid gland

-

Abnormal stimulation of these cells causes over production of the thyroid hormone and symptoms of hyperthyroidism.

Type I Diabetes: -

Molecular mimicry has been implicated in sensitization of cytotoxic T cells to attack and lyse insulin- producing beta cells.

-

A recent study showed permanent reversal of type 1 diabetes by re-infusion of stem cells after complete immune suppression.

Multiple sclerosis: -

Paralyzing neuromuscular disease associated with lesions on the myelin sheath of nerves and white matter of the nervous system.

-

T cell and autoantibody-induced damage compromises the capacity of neurons to send impulses.

-

Symptoms include muscle weakness, tremors, difficulties in speech and vision, and paralysis.

-

Possible association between infection with human herpesvirus 6

-

Treatments include immunosuppressants and interferon beta.

Immunodeficiency Diseases: Hyposensitivity of the Immune System •

Occasionally, an individual is born with or develops weakened immune responses.

•

Results in recurrent, overwhelming infections with opportunistic microbes.

Primary Immunodeficiency Diseases •

Primary at birth (congenital)

•

Lymphocytes may be absent, reduced or present but not functional

•

An individual can lack either B or T cells, or both.

•

Some deficiencies can affect other immune system components as well.

•

Clinical Deficiencies in B-Cell Development or Expression -

Genetic deficiencies in B cells usually result in abnormal immunoglobulin (Ig) expression: -

In some cases, certain classes of Igs are absent (agammaglobulinemia).

-

In other cases, levels of Ig are reduced (hypogammaglobulinemia). •

•

(most common hypogammaglobulinemia).)

Clinical Deficiencies in T-Cell Development or Expression -

More devastating than B-cell deficiencies. Because T helper cells are required to assist in most specific immune functionsIf you don’t have B cells you don’t have T cells and vice versa

-

Defects in T-cell development result in a broad spectrum of diseases: -

Severe opportunistic infections

-

Cancer

-

An individual can lack B ot R cells

-

Can affect other cells functions as well

Secondary Immunodeficiency Diseases: acquired after birth and caused by natural or artificial agents •

Caused by one of four general agents: 1. Infection 2. Chemotherapy 3. Noninfectious metabolic disease 4. Radiation

•

Most recognized infection-induced immunodeficiency is AIDS: -

Depletion of T-helper cells and impairment of immune responses account for cancers and opportunistic infections caused by AIDS....