Immune System Chapter 16 Immune system Immunity the

Immune System Chapter 16

Immune system • Immunity- the body’s ability to protect itself from disease-causing entities (pathogens)

Immune system functions • Recognize/remove abnormal “self” cells – Abnormal cell growth and development • Removes dead/damaged cells – e. g. , old red blood cells • Protects from pathogens (disease causing invaders) – Any exogenous molecule/cell

Immune cells • Leukocytes (white blood cells) • Most circulate in blood but leave and function extravascularly • Some live in tissues

Immune response • Two categories – Innate (nonspecific) – Acquired

Innate immunity Present from birth Nonspecific immune response Quick Immune cells are genetically programmed to respond to a broad range of foreign material • Either clears infection or contains it • •

Innate immunity – Physical barriers (first line of defense) – Chemical

Innate immunity • If pathogens get past physical/chemical barrier, immune cells respond • Natural killer (NK) cells • Phagocytes

Innate immunity • Inflammation – Immune cells release cytokines – Cytokines attract other immune cells and increase capillary permeability – Benefits: • Attracts immune cells to site • Produces physical barrier

Innate immunity • Fever – Stimulates immune cell proliferation – Elevated body temp has indirect effect on microbes

Acquired (adaptive) immunity • Third line of defense • Distinguishes self from non-self • Targets specific antigens • Substance that stimulates immune response • Typically on surface of cells

Acquired immunity • Mediated primarily by lymphocytes • T lymphocytes – Cells that attack and destroy virus-infected cells (killer T) – Cells that direct other immune cells (helper T) • B lymphocytes- develop into plasma cells that secrete antibodies

Killer T • Release cytotoxins to destroy infected cells

Helper T cells • Produces proteins to activate killer T cells and B cells

B cells • Group of lymphocytes specific to one antigen • Determined by receptor • Only a few of each clone, unless pathogen enters, then they reproduce

Antibodies • Protein that detects pathogens • Produced by plasma cells • Free antibodies bind to antigens and signal to immune cells to destroy

Acquired immunity • Repeated exposures, increased number of cells with memory, allows for more rapid reaction

Acquired immunity • Two categories – Active immunity- exposure to pathogen, body produces its own antibodies (natural or artificial) – Passive immunity- acquisition of antibodies made by another organism (natural or artificial)

Artificially acquired active immunity- Vaccines • Expose individual to live or killed pathogen to stimulate antibody production and antigen memory

Pathogens • Viral- infectious agent that replicates only inside the living cells of other organisms • Bacterial- free living, single celled, group of microorganisms • Parasites- lives in/on a host and gets its food from/at expense of host

Viral life cycle • Take over of a host’s cell

Immune system pathologies • Incorrect responses – Failure to distinguish self from non-self, autoimmune disease • Overactive responses – Response out of proportion to threat, allergies • Lack of response – AIDS

Incorrect response • Failure of an organism in recognizing self • Immune response against its own cells/tissues • Autoimmune disease – Can be triggered by an infection (foreign antigens that are similar to human antigens)

Autoimmune diseases • Celiac disease • Gluten is modified by an enzyme in the small intestines • The immune system attacks gluten at the epithelial cells of the bowels • Causes damage to the villi, which interferes with nutrient absorption

Autoimmune diseases • Multiple sclerosis • T cells recognize myelin as foreign and attacks • Release of cytokines attracts other immune cells, inflammation

Overactive response • Allergic reactions • Same process as regular immune reaction • Can be from almost anything (organic, inorganic, natural, synthetic) • Appears to have a genetic basis

Lack of response • One or more components of the immune system are inactive • E. g. , Immune system fails to recognize intruders • E. g. , Immune system can’t keep up with intruder mutations

Human Immunodeficiency Virus (HIV) • Transmission- bodily fluids in contact with mucous membranes • Viral infection that attacks helper T cells • Interruption of helper T activity means no communication with B and killer T cells • Allows for opportunistic infection

HIV • Virus replicates, eventually induces death of T cell host • Viral load increases in the body • Fewer T cells, stresses immune system

HIV/AIDS • Primary infection- HIV destroys T cells • Latent infection- decline of production of T cells • Acquired immunodeficiency syndrome (AIDS)- T cell count less than 200

AIDS • Body can’t fight off other opportunistic infections • People die from secondary infections, rather than from the virus itself

Secondary infections • • Candidiasis Cancer (Kaposi’s sarcoma) Pneumonia Many others • Cryptococcal Infection

HIV treatment • Mutation rate is high, new strain every two days, drugs don’t recognize new strains • Virus can become immune, especially to single drug treatments • Patients typically given a cocktail of drugs