Lec: Immune System

Immune system

recognizes bacteria and fungi by structures on their cell walls

• recognizes foreign bodies = “not self”

• responds with the production of immune cells and proteins

Innate immunity

present before any exposure to pathogens and is effective from the time of birth

• consists of external barriers

• internal cellular

• chemical defense

recognition of traits shared by board ranges of pathogens, using a small set of receptors

Acquired immunity

adaptive immunity, develops after exposure to microbes, toxins, or foreign substance

• very specific response to pathogens

recognition of traits specific to particular pathogens, using a vast array of receptors

Phagocytosis

the ingestion and digestion of foreign substance including bacteria

Innate immunity defenses

include barrier defense, phagocytosis, antimicrobial peptides

• additional defense: inflammatory response and natural killer cells

Barrier defense

the skin and mucous membrane of the respiratory, urinary, and reproductive tracts

• many body fluids, saliva, mucus and tears

• the low pH of the skin and digestive system prevents growth

Cellular innate defenses

white blood cells= leukocytes

• engulf pathogens in the body via phagocytosis

• pathogens are recognized by TLR, toll-like receptors

types of phagocytic cells

• Neutrophils: engulf and destroy microbes

• Macrophages: are part of the lymphatic system and are found throughout the body

• Eosinophils: discharge destructive enzymes

• Dendritic cells: stimulate development of acquired immunity

Antimicrobial peptides and proteins

peptide and proteins function in innate defenses by attacking microbes directly or impeding their reproduction

• interferon: proteins provided innate defense against viruses and help activate macrophages

Inflammatory response

following an injury, mast cells release histamine

• promotes changes in blood vessels

• these changes increase local blood supply and allow more phagocytes and antimicrobial proteins to enter tissue

Pus

a fluid rich in white blood cells

• dead microbes

• cell debris

• “battle field”

Fever

a systemic inflammatory response triggered by pyrogens (release= fever)

Septic shock

life threatening condition caused by an overwhelming inflammatory response

• bacteria attack blood —> lead to organs —> attack on organs

MHC I

all body cells have MHC protein on their surface

• protein attachment

• found on almost all nucleated cell of the body

MHC II

protein molecule found on specialized cells

• special access

• T & B cells

• located on dendritic cells, macrophages, b cells

T cells

Lymphocytes that mature in the thymus above the heart

• has receptor proteins that bind to foreign molecules

• consist of two different polypeptide chains: V region and C region

• bind to an antigen that is free, fragments presented on a host cell

B cells

Lymphocytes that mature in the bone marrow

• has receptor proteins that bind to foreign molecules

• give rise to plasma cells, secrete proteins = antibodies or immunoglobulins

• bind to specific, intact antigens

• consists of two identical heavy chains and two identical light chains

MHC molecules

Antigen presentation = bind and transport antigen fragments to the cell surface

• call for help

Clonal selection

lymphocytes with antigen receptors for epitope, induces the lymphocytes to divide rapidly

two types

1. effector cells

2. memory cells

effector cells

short lived cells, fight current battle

memory cells

long lived memory cells, for future attacks by same pathogen

Primary immune response

first exposure to specific antigen

• effector B cells= plasma cells are generated,

• T cells activated to their effector forms

Secondary immune response

memory cells facilitate faster, more efficient response

Humoral immune response

Acquired immunity: activation and clonal selection of B ells.

• production of secreted antibodies

Cell-mediated immune response

Acquired immunity: activation and clonal selection of cytotoxic T cells

CD4

surface protein, binds to class II MHC molecule

• keeps helper T cell joined to antigen-presenting cell

• activated T cell secrete cytokines

POSITIVE FEEDBACK in the immune system enhances the process until some endpoint or maximum rate is reached

CD8

made from Cytotoxic T cells, surface protein (angry)

• enhances interaction between a target cell and a cytotoxic T cell

• makes into active killer

• secretes proteins that destroy the infected target cell

Active Immunity

develops naturally in response to an infection

• also develop following from immunization = vaccination

• immunological memory

Passive Immunity

provides immediate, short term protection

• can be artificially by injecting antibodies into nonimmune person

• ex. mother to infant in breast milk