Understanding the Immune System

The Immune System

• Defends the body against disease and damaging foreign entities
• Essential for survival by identifying viruses, bacteria, and parasites
• Guards against disease and tissue damage
• Immune cells concentrate in blood and lymphatic tissue
• Functions include defense against invading organisms
• Cleans up and removes damaged tissue
• Surveillance by identifying and destroying abnormal body cells

Major components of the immune system

• Lymph Nodes
• Spleen
• Bone Marrow
• Lymphocytes that consist of:
  • B-cells make antibodies that attack toxins
  • T-cells kill pathogen-infected or damaged cells
  • Helper T-cells determine immune response to a particular pathogen
• Thymus
• Leukocytes

Why We Need an Immune System

• Protects from invaders
• Guards against external threats like bacteria, viruses, pollution, and allergens
• Defends against internal threats

Timing of Immune System Function

• Starts to develop in utero
• Always working

First Line of Defense: Non-Specific & Innate Immunity

• Consists of mechanical and chemical barriers
• Skin and mucous membranes
• HCL acid
• Tears and saliva
• Cilia
• Wax

Normal Microbiome

• Body surfaces are colonized by unique bacteria and fungi
• It does not cause disease when immune systems are functioning
• Opportunistic infections can occur otherwise

Second Line of Defense: Non-Specific & Innate Immunity

• Phagocytes are WBCs that eat and destroy pathogens
• Inflammation is the body's response to infection and injury
  • Erythema (redness)
  • Edema (swelling)
  • Heat
  • Pain
• Pyrogens travel to the hypothalamus, which is responsible for temperature, producing a fever
• Cytokines stop the spread of viruses to new cells
  • Interferons
  • Interleukins
• Complement proteins enhance the action of antibodies

Phagocytosis

• Involves neutrophils and macrophages

Inflammation

• Body aims to self-protect, remove harmful stimuli, and begin healing
• Infections, wounds, and tissue damage would not heal without an inflammatory response
• Chronic inflammation causes more diseases and conditions

Third Line of Defense: Specific & Acquired Immunity

• Lymphocytes are WBCs that target specific pathogens
• Both T and B cells need to encounter a pathogen before responding
• Both T and B cells develop memory
• T Cells:
  • Originate from the thymus gland
  • Recognize and target cells that are wrong
• B Cells:
  • Originate from bone marrow
  • Produce antibodies that bind to foreign material

Immunity

• Active Immunity:
  • Gained through actively engaging with an antigen through invasion or vaccination
  • Examples include building resistance to a disease or fighting off a cold
• Passive Immunity
  • Receives antibodies made outside the body by another person, animal, or recombinant DNA
  • Breastfeeding

CD Molecules

• Surfaces are expressed on immune cells
• They play crucial roles in cell-to-cell communication
• They are essential markers for identifying and isolating leukocytes and lymphocyte subsets.

Immunoglobins (Antibodies) Classes

• These have specificities for particular antigens
• IgG is the most abundant and accounts for most protective activity against infections
• IgA is found in blood and body secretions

Disorders of the Immune System

• Complications arise when the immune system does not function properly
• Minor effects
  • Allergies
• Extensive effects
  • Cancer
  • Genetic disorders
  • Immune deficiency
  • Autoimmune diseases
  • Sepsis

Hypersensitivity

• Body responds in an exaggerated fashion to a substance
• Inflammation and destruction of healthy tissue occur
• Reactions can be immediate or delayed
• Four types of reactions that can be produced by the immune system

Types of Hypersensitivity Reactions

• Type I is Immediate IgE Mediated, such as Hay fever, food allergies, and anaphylaxis
• Type II is Tissue Specific, where IgG or IgM reacts with an antigen
• Type III is Immune Complex Mediated, where the antigen-antibody complexes are deposited in tissues and autoimmune disorders occur
• Type IV is Cell Mediated, where antigen processing is delayed

Type 1 Hypersensitivity - Immediate

• Allergies occur when the body has a hyper-response to a foreign material.
• Localized Responses:
  • Itchy eyes
  • Runny nose
  • Scratchy throat
  • Hives
  • Digestive issues
• Systemic Response:
  • Anaphylactic shock causes respiratory and circulatory collapse.

Type 2 Hypersensitivity - Cytotoxic

• Characterized by blood transfusion reactions related to blood types

Type 3 Hypersensitivity - Immune Complex Reaction

• Autoimmune disorders in which the body attacks self tissue

Type 4 Hypersensitivity - Delayed

• Characterized by slower reactions because it takes 48-72 hours to develop after exposure
• Mediated via T lymphocytes

Autoimmune Disorders

• Normal defenses become self-destructive and recognize themselves as foreign
• Causes are usually unclear
• These disorders affect women more than men
• Affect some or all tissue
• Characterized by remission and exacerbation
• Triggered by stress
• Hard to diagnose
• Treatments include meds and methods to manage stress

Systemic Lupus Erythematosus (SLE)

• Inflammatory autoimmune disorder affecting connective tissue
• Has B cells for unknown reasons, producing AB and AG, forming Immune Complexes(IC)
• ICs attack body's own tissue
• To get diagnosis, patient needs 4 of 11 factors:
  • Butterfly rash across cheeks
  • Skin rashes
  • Photosensitivity
  • Mucous membrane ulcers
  • Joint inflammation
  • Arthritis
  • Fever
  • Pain
  • Fatigue
  • Pleuritis or Pericarditis
  • Renal abnormalities
• Treatment involves improving prognosis with early diagnosis

Transplants

• Graft: Tissue taken from one part of body and used in another that matches the best tissue antigens
• Donor sources may be cadavers or living
• Graft types
  • Autograft is from the same person
  • Isograft is from an identical twin
  • Allograft is from the same species
  • Xenograft is from a different species

Transplant Reactions

• Donor organ does not work
• Patient is non-adherent
• Rejection based on timing in 3 types
  • Hyper-acute is called immediate
  • Acute happens in 4 days to 3 months
  • Chronic happens 4 months to years

Rejection Reactions [type 4]

• Host versus Graft: The host is fighting the graft
• Graft versus Host: The graft is fighting the host
• First sign is organ failure
• Treatment:
  • Prevention
  • Immunosuppressive Therapy

Immunodeficiency

• Diminish or absent immune response
• Increases chances of susceptibility to infections
• Genetic loss of one or more lines of defense
• Born with this condition
• Must be given opportunistic infection that does not cause disease in healthy individuals
• Treat with measuring immunoglobin levels
• Treat with WBCs and Lymphocytes
• Treatment:
  • Bone Marrow Transplant
  • Reverse isolation precautions
  • Hand washing
  • limiting visitors
  • Avoiding flowers

At-Risk Individuals for Immune Dysfunction

• Very young and very old
• Poor nutrition
• Impaired skin integrity
• Circulatory issues
• Alterations in normal flora due to antibiotic therapy
• Chronic diseases especially diabetes mellitus
• Corticosteroid therapy
• Chemotherapy
• Smoking
• Alcohol consumption
• Immunodeficiency states

Strategies for Building Immune Systems

• Increase fluid intake
• Eat a balanced diet
• Increase antioxidants and protein intake
• Get enough sleep
• Avoid caffeine and refined sugar
• Spend time outdoors
• Reduce stress

Replacement Therapies for Immune Deficiencies

• Gamma Globulin Therapy
• Transplantation and Transfusion

4 Stages of Infection

• Incubation period is where there is an organism growing and multiplying.
• Prodromal stage occurs when a person is most infectious and shows nonspecific signs of disease.
• Full stage of illness has specific signs and symptoms.
• Convalescent period begins with recovery from the infection.

Shapes of Bacterial Invasion

• Spherical (Cocci): Streptococcus pyogenes can cause strep throat
• Rod-Shaped (Bacilli): Bacillus anthracis causes Anthrax
• Spiral-Shaped: Vibrio cholerae causes Cholera

Common Bacterial Infections

• Central Nervous System (Meningitis): Streptococcus pneumoniae, Neisseria meningitidis, and Haemophilus influenzae
• Mouth: Prevotella spp., Streptococcus spp., and Actinomyces spp.
• Intra-Abdominal: Enteric Gram-negative rods, Enterococcus spp., and Streptococcus spp.
• Urinary Tract infections are Escherichia coli and Proteus spp
• Respiratory Tract infections include Staphylococcus aureus, Haemophilus influenzae, and Streptococcus spp
• Skin/Soft Tissue infections are Staphylococcus spp. And Streptococcus pyogenes

Fungus

• Infection is mycosis
• Candida spp. are hematogenously disseminated infections
• Pneumocystis spp produce pneumonia
• Histoplasma capsulatum causes acute pneumonia
• Cryptococcus spp causes pneumonia and meningitis

Malaria

• Transmitted by mosquitoes is life-threatening
• Preventable and curable
• Children under 5 years of age are the most vulnerable group

AIDS (Acquired Immunodeficiency Syndrome)

• Immune Deficiency is a result from HIV, Pneumonitis, and damages brain leading to Arthritus
• There are three stages of progression:
  • 1- Acute HIV Infection can feel like the flu.
  • 2- Clinical Latency might not show systems. They are mostly not symptoms.
  • 3- AIDs has CD4 count of less than 200 cells.
• There is no cure for either disease, but transmissions of body fluids can cause both
• Testing can detect if there is anibody or antigen
• Should be treated with antiretroviral therapy
  • Transmissions can be prevented
  • CD4 count must remain low