Immunity and InfectionImmunity and Infection

Chapter 17

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The Chain of InfectionThe Chain of Infection Links in the chain

Transmitted through a chain (six links) Pathogen - disease causing microorganism Reservoir - natural environment of the pathogen: person, animal, or

environmental space such as soil or water Portal of exit – saliva, mucous membranes, blood, feces, nose Means of transmission

Direct transmission – sneezing, coughing Indirect transmission – rats, ticks, mosquitoes

Vectors – carrier of the pathogen from one host to another Portal of entry

Direct contact with or penetration of the skin Inhalation through mouth or nose Ingestion

New host Breaking the chain at any point can prevent disease

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Figure 17.1 The Chain of InfectionFigure 17.1 The Chain of Infection

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The Body’s Defense SystemThe Body’s Defense System Physical and chemical barriers

Skin, mucous membranes, respiratory tract

The Immune System Immunological Defenders

Neutrophils Macrophages – “big eaters” Natural killer cells Dendritic cells – eat pathogens and activate lymphocytes Lymphocytes

T-cells Helper, killer, and suppressor

B-cells Memory cells

Antigens and antibodies “Self” versus “non-self”

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Figure 17.2 The Lymphatic SystemFigure 17.2 The Lymphatic System

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Inflammatory and Immune ResponsesInflammatory and Immune Responses Histamine

Dilation of blood vessels, heat, redness, swelling The immune responses: natural and acquired

Phase 1 – Dendritic cells are drawn to the site Phase 2 – helper T cells multiply

Production of killer T and B cells Cytokines – chemical messengers

Phase 3 – killer T cells strike Cell-mediated immune response Antibody-mediated immune response

Phase 4 – last phase Slow down activity Debris excreted from body

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Figure 17.3 The Immune ResponseFigure 17.3 The Immune Response

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ImmunityImmunity An infected person may never get the same

illness again Lymphocytes reserved by memory T and B cells =

acquired immunity Symptoms and contagion

Incubation – when viruses are multiplying in the body or when bacteria are actively multiplying

Will not feel symptoms until the second or third phase of the immune response cycle

Prodromal period – symptoms first appear, but the infected host may have acquired immunity

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Epidemics and PandemicsEpidemics and Pandemics Epidemic: a rapidly spreading (greater than

expected) disease or health-related concern Pandemic: widespread epidemics Results only if three criteria are met:1. Little or no pre-existing immunity to the new virus2. Efficient human-to-human transmission of the virus3. New virus can cause illness May occur in specific populations or regions

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ImmunizationImmunization The process of priming the body to remember an

encounter with a specific antigen Types of vaccines

VACCINE- Introduction of a killed or weakened pathogen to stimulate the body to produce antibodies

ACTIVE IMMUNITY - person produces his or her own antibodies to the microorganism

PASSIVE IMMUNITY- injection of antibodies produced by other human beings or animals

ACQUIRED IMMUNITY- the ability of a memory lymphocytes to remember a previous infection (chicken pox)

Table 17.2 Immunizations Recommended for Teens and College Students

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Immunization IssuesImmunization Issues

Vaccine shortages in the U.S. Vaccine safety Are they really worthwhile?

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Allergy: The Body’s Defense Allergy: The Body’s Defense System Gone HaywireSystem Gone Haywire Allergies: body defends against harmless

substances Allergens: substances that provoke allergies

Pollen, animal dander, dust mites and cockroaches, molds, food, insects

Allergic response: due to antibody Immunoglobulin E (IgE) Anaphylaxis

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Figure 17.4 The Allergic Figure 17.4 The Allergic ResponseResponse

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Dealing with AllergiesDealing with Allergies Avoidance Medication Immunotherapy or “allergy shots”

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Figure 17.5 PathogensFigure 17.5 Pathogens

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Pathogens and DiseasePathogens and Disease Pathogens: bacteria, viruses, fungi, protozoa, parasitic

worms, prions Bacterium – microscopic single-celled organism

Pneumonia Meningitis Strep throat and other streptococcal infections Toxic shock syndrome and other staphylococcal infections Tuberculosis Tickborne infections Ulcers Other bacterial infections

Tetanus, Clostridium difficile, pertussis, urinary tract infections

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Antibiotic TreatmentAntibiotic Treatment

Actions of antibiotics Antibiotic resistance Proper antibiotics usage

Don’t take an antibiotic every time you are sick; effective for bacteria, ineffective for virus

Use antibiotics as directed; finish full courseNever take an antibiotic without an

prescription

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VirusesViruses Viruses are parasites – they take what they need Most common contagious disease

Common cold Influenza Measles, mumps, rubella Chicken pox, cold sores, and other herpesvirus infections

Varicella-zoster virus Herpes simplex virus (HSV) types 1 and 2 Epstein-Barr virus (EBV) (causes mononucleosis)

Viral encephalitis Viral hepatitis (A, B, C) Poliomyelitis Rabies Human papillomavirus (HPV)

Treating viral illnesses

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Figure 17.6 Life Cycle of a VirusFigure 17.6 Life Cycle of a Virus

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Types of PathogensTypes of Pathogens Fungi

Primitive plant – yeast infections, athlete’s foot, jock itch, ringworm Candida albicans

Protozoa Microscopic single-celled animal: malaria, giardiasis, trichomoniasis,

trypanosomiasis, amoebic dysentery Parasitic worms

Largest organism that can enter the body to cause infection: tapeworm, hookworm, pinworm (most common)

Prions Fatal degenerative disorders of the CNS linked to “proteinaceous

infectious particles” or prions Lack DNA and RNA Transmissible spongiform encephalopathies (TSEs)

Spongelike holes in the brain Creutzfeldt-Jakob disease in humans Bovine spongiform encephalopathy (BSE) or “mad cow disease” in cattle

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Emerging Infectious DiseasesEmerging Infectious Diseases Selected infections of concern:

West Nile virus Severe acute respiratory syndrome (SARS) Rotavirus Escherichia coli 0157:H7 Hantavirus Ebola

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Factors Contributing to Emerging Factors Contributing to Emerging InfectionsInfections Drug resistance Poverty Breakdown of public health measures Travel and commerce Mass food production and distribution Human behaviors Bioterrorism

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Other Immune Disorders: Cancer Other Immune Disorders: Cancer and Autoimmune Diseasesand Autoimmune Diseases

If the immune system breaks down Getting older Certain immune disorders (HIV) Chemotherapy

Autoimmune diseases Rheumatoid arthritis Systemic lupus erythematosus

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Support Your Immune SystemSupport Your Immune System

How to support your immune systemGeneral guidelines

Balanced diet Enough sleep Exercise Don’t smoke Moderation of alcohol Wash your hands Avoid contact with contagious people

Plenty of clean water Avoid contact with vermin Practice safe sex Do not use injectable drugs Vaccinations

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IMMUNITY AND INFECTIONIMMUNITY AND INFECTIONChapter 17

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