Class 3 - Alterations in Immune Response

Question 1

Adaptive / Acquired Immunity

Answer 1

• Third line of defence

Characteristics

• Specificity: pathogen specific response
• Memory: long term protection
• Inducible: by vaccinations
• Self-tolerance: identifies substances that are self and non-self

Humoral B cells

• Produces antibodies
• Bacteria and viruses

Cellular T cells

• Reacts directly with antigen on cell surfaces
• Viruses and cancer cells
• Helper T cells stimulate B cels

Question 2

Hypersensitivty

Answer 2

• Excessive or inappropriate immune response to an antigen that results in disease or damage to the host
• Includes allergy, autoimmunity and alloimmunity
• May be either antibody mediated B cells or cell mediated T cells

Question 3

Allergy

Answer 3

• An immune response to an environmental antigen

Question 4

Autoimmunity

Answer 4

• Disturbances in the immunological tolerance of self antigens
• The body recognizes self-antigens as foreign
• Cause not clearly understood: heredity, gender, infection, and drugs?
• More common in females

Question 5

Allotimmunity

Answer 5

• Immune reaction to tissues of another individual

- Transplant / graft rejection

Question 6

Mechanisms of Hypersensitivity

Answer 6

Type I
- IgE mediated
- Mast cells degranulate 
Type II
- IgM and IgG mediated
- Antigen-antibody complex forms on the cell surface
Type III
- IgM and IgG mediated
- Antigen-antibody complexes formed during circulation and is later deposited in different tissues
- Antigen and antibody are bound together 
Type IV
- Cell mediated by T cells

• Types I, II and III are mediated by B cells

Question 7

Type I Allergy

Answer 7

• Against environmental antigens. Takes at least 2 exposures
• IgE mediated.
• IgE binds to receptors on the surface of mast cells. The host is sensitized.
• Subsequent exposure: the allergen binds directly to IgE on the mast cell
  1. The mast cell degranulates (dissolves) and releases histamines
  2. Histamine binds with H1 receptors that cause symptoms
  3. Histamine causes vasodilation and increased permeability of capillaries

Systems most affected:
- skin, respiratory, GI tract

Question 8

Manifestations of Type I Allergy

Answer 8

• Itching
• Urticarial (hives)
• Conjunctivitis
• Rhinitis (inflammation of the mucous membrane in the nose)
• GI cramps and malabsorption

Question 9

Anaphylactic Reaction - Type I Allergy

Answer 9

• Genetic predisposition (atopic)
• Life threatening allergic reactions

Manifestations

• Wheezing and difficulty breathing
• Hypotension and tachycardia
• GI - nausea, vomiting, diarrhea
• Systemic, not local

Medication / Reaction

• First line: epinephrine
• Others: corticosteroids, antihistamines. These won’t be helpful in preserving and maintaining ABC’s

Question 10

Type II Hypersensitivity Reaction

Answer 10

• IgG and IgM mediated
• Tissue specific. Immune response to proteins only on certain cell membranes
• Cells are lysed or phagocytize: thrombocytopenia (low blood platelet count), and transfusion reactions

Question 11

Hemolytic Disease of the Newborn

Answer 11

Type II Hypersensitivity Reaction

• Occurs with a mom who is Rh- and baby is Rh+
• Begins to occur in the 36-37 week of pregnancy with the first baby, mom is exposed to Rh factors
• Mom produced antibodies to Rh factors
• With subsequent pregnancies, the antibodies cause hemolysis (breakdown of RBC’s) in the fetus
• Mild outcomes: jaundice. To help get rid of jaundice, put under UV “bilirubin lights” to help break down bilirubin faster
• Severe outcomes: multiple miscarriages

Prevention:

• Prevent the formation of antibodies in the first pregnancy
• Uses injection of RH immune globulin (rhogam)
• Used for Rh- moms on their first pregnancy

Identification for at risk babies

• Use fetal Rh testing
• Intrauterine transfusion
• Exchange transfusion after the baby is born to remove most of the hemolyzed RBC’s

Question 12

Type III Hypersensitivity Reaction

Answer 12

• IgG and IgM mediated

- Antigen-antibody complexes are formed in circulation and are later deposited in vessel walls or extravascular tissues

Question 13

Systemic Lupus Erythematous (Lupus)

Answer 13

Type III Autoimmunity

• Antigen-antibody complexes form and circulate in plasma then deposited in various tissues and organs
• Skin, muscle and bone, heart, kidneys, lungs, reproductive organs, nerves

Clinical Manifestations

• Arthralgia or arthritis 90%
• Vasculitis and rash 70-80%
• Renal Disease 40-50%
• Hematologic changes 50%
• Cardiovascular disease 30-50%

Diagnostic: must have 4 of 11 cardinal

• Facial rash - butterfly pattern, can also occur on neck and upper shoulders
• Discoid rash (raised, scaling)
• Photosensitivity
• Oral or nasopharyngeal ulcers
• Arthritis
• Inflammation of lung or heart membranes
• Renal disorder
• Neurologic disorder
• Immune disorder
• Presence of antibodies

Question 14

Type IV Hypersensitivity Reaction

Answer 14

• Does not involve B cells / antigen-antibody
• Involves T cells
• Contact dermatitis, skin test for tuberculosis, poison ivy, acute organ rejection

Acute organ rejection:

• Uses T cells
• T cell response to unmatched HLA antigens
• Occurs within days to months after transplantation

Question 15

Preventing Organ Rejection

Answer 15

• Tissue typing HLA: human leukocyte antigen matching
• Immunosuppressive techniques:
  1. Corticosteroids: suppresses immune response, will slow healing after transplant, but still necessary, higher risk for infections
• Cytotoxic drugs: destroy lymphoid tissue
• Anti-lymphoserum: specific to T cells

Question 16

Immune Deficiencies

Answer 16

• Failure of immune mechanisms of self defence
• Primary (congenital) immunodeficiency
• Secondary acquired immunodeficiency (more common)
• Clinical hallmark is the development of unusual or recurrent, severe infections
• B cell deficiencies (humoral): recurrent and life-threatening bacterial infections
• T cell deficiencies (cellular): viral, fungal, yeast, atypical microorganisms, and cancers

Question 17

DiGeorge Syndrome

Answer 17

Primary T-lymphocyte Deficiency
- Due to a partial lack of thymus
CATCH
- Cardiac and aortic defects
- Abnormal facial features
- Thymic aplasia/hypoplasia
- Cleft palate
- Hypocalcemia/hypoparathyroidism

Question 18

Secondary (Acquired) Deficiencies

Answer 18

• More common than primary deficiencies
• Normal physiology conditions aging

Complications of other conditions:

• Infancy, aging and pregnancy
• Stress
• Dietary insufficiencies
• Malignancies
• Medical treatments (chemotherapy, corticosteroids)
• Trauma, like burns
• Other diseases (diabetes, SLE)

Question 19

AIDS

Answer 19

Secondary Acquired Deficiencies

• Caused by HIV
• Depletes the body’s CD4 T-helper cells
• CD4 T cells needed for development of both plasma cells (antibodies) and cytotoxic T cells
• Incidence of HIV infection:
  1. In Canada, 20% don’t know they have HIV
  2. Globally, 50% don’t know

Diagnosis:

• Opportunistic and severe infections and cancers
• CD4 T-helper cells <200 cells/mm3

Question 20

HIV

Answer 20

• Effective antiviral therapies have made HIV a chronic disease

Epidemiology:

• Blood born pathogen is transmitted through sexual contact, blood to blood contact, through the placenta, contact with blood at birth, or through breastfeeding
• Increasing faster in women than in men
• Globally, most important mode fo transmission is heterosexual contact

Stages:

1. Acute Infection:
   - Within 2-4 weeks of infection
   - Flu like symptoms
   - Antibodies usually appear within 4-7 weeks of exposure
   - Can remain sero-negative for 6-14 months
2. Clinical Latency:
   - Asymptomatic
   - With treatment, may last several decades
3. AIDS
   - Vulnerable to infections and cancers

Diagnosis:

• Presence of the virus
• Decreased CD4 T-helper cells

Question 21

General Treatment for Immunodeficiency’s

Answer 21

• Place missing component of the immune system
• Gamma globulin therapy
• Transplantation: bone marrow, thymus transplant (DiGeorge), stem cell
• Gene therapy

Question 22

Immune Response and Stress

Answer 22

• Direct innervation from ANS to: Thymus, spleen, lymph nodes, lymphoid tissue, bone marrow
• Receptors on immune cells for stress hormones and neurotransmitters
• Increased cortisol, norepinephrine and epinephrine during stress:
  1. Cause atrophy of the thymus (fewer T cells). This creates less resistance to infections, cancer, and more chronic sustained stress
  2. Increases antibody response (B cells). Causes increased allergies and autoimmune reponses
  3. May enhance or suppress inflammatory response

Stress and Disease known links to:

• Coronary disease
• Cancers
• Infections
• Type 2 Diabetes Mellitus
• Asthma
• Psychological disorders: depression, PTSD, Anxiety
• Accelerated aging