Immunity

Role: Defense Three major types of defense: - Physical and chemical barriers - Non-specific defense  use various means - Specific defense: Immunity

Physical and chemical barriers Physical barriers: - skin, mucous, flow of tears, urine, saliva, earwax, defecation, vomiting Chemical barriers: -Enzymes in the stomach, on the skin, in tears, saliva -Low pH of gastric juice, vaginal secretions -Resident bacteria

Non-specific defenses Phagocytosis Inflammation Natural killer cells Complement system Interferon Fever

Phagocytosis

Inflammation

Natural killer cells Kill cells by perforing the membrane Promote inflammatory response Especially active against viral infections and cancerous cells

Complement system

Interferon

Fever Triggered by pyrogens, substances secreted by macrophages Slow down bacterial growth

Specific defense: Immunity Two categories : -Antibody-mediated immune response (AMI)  against pathogens extrernal to the cell (bacteria, fungi) -Cell-mediated immune response (CMI)  against pathogens internal to the cell (virus, cancer)

Characteristics It recognizes and targets specific pathogens or foreign substances, known as antigens It has memory It protects the entire body

What are antigens Antigens are proteins that are foreign to a body

What about our own cells? They have proteins on the cell membrane. These proteins define our identity and differentiate us from other beings These “self-markers” are known as the “Major Histocompatibility Complex” or MHC The immune system is able to differentiate between the two types of proteins

The main players Macrophages   B lymphocytes Killer T lymphocyte   Helper T Lymphocytes (and a macrophage)

AMI Goal: Attack external pathogens such as bacteria, fungi Cells involved: Macrophages, B lymphocytes (=B cells), plasma cells and helper T lymphocytes

Antibodies Role: Flag the pathogen (do not kill it directly) Promote phagocytosis Five types of antibodies - IgG: in the plasma, most abundant, long life, can cross the placenta - IgM: largest, first to respond, cannot cross the placenta - IgA: in mucous membranes, external secretions, throughout body - IgD: in lymph, on B cells - IgE: on B cells, mast cells, and basophils, trigger allergic responses

Antibody

CMI Goal: Attack internal pathogens such as virus infected cells and cancerous cells Cells involved: Macrophages, Killer T (or cytotoxic) lymphocytes (=killer T cells), plasma cells and helper T lymphocytes

AMI and CMI

Primary and secondary immune response

Types of immunization ActivePassive Natural Artificial

Bacterial resistance to antibiotics

Allergic reactions

Tissue rejection Implanted organs have a high risk of rejection, since no two persons are alike (except identical twins) Cell-mediated immunity is responsible for the reaction Upon receiving an organ, a person must take antirejection medications for life

Autoimmune disorders Lupus erythematosus: inflammation of the connective tissue Rheumatoid arthritis: Inflammation of the synovial membrane (joints) Diabetes mellitus, type I: destruction of the cells synthesizing insulin Multiple sclerosis: destruction of the sheath surrounding the axon of the nerve cells

Ebola vs Flu vs Cold

Human Immunodeficiency Virus

HIV prevalence