BIOL163 - IMMUNITY

lymph flow

interstitial fluid enters lymphatic capillaries, is filtered by white blood cells in lymph nodes, and transported back to the bloodstream at the left and right subclavian veins

lymph nodes

house the white blood cells that help with immunity

lymph

enters the node and travels through spaces called sinuses

sinuses

location of white blood cells

capillaries

provide oxygen and nutrients for the cells

pathogens

varied and cause disease/infection in a host organism, this leads to an immune response

nonspecific defenses (attack any pathogen)

external barriers, phagocytic cells, natural killer cells, fever, inflammation

specific defenses (attack a specific, identified pathogen)

cell-mediated immunity, antibody-mediated immunity

antigens

molecules that have the potential to generate antibodies (create an immune response)

antigens

most commonly proteins or carbohydrates found in the plasma membrane, envelop (virus), or cell wall of pathogens

antibodies

(proteins) only interact with specific antigens

self-antigens

normally do not trigger a response

non-specific defenses

mechanisms that respond to all pathogens in the same way

external barriers

integumentary system (skin) -dryness/acidity, mucous membranes - trap pathogens

physical barriers

prevent approach of and deny access to pathogens

phagocytic cells

remove pathogens by engulfing them, includes dendritic cells and macrophages

phagocytes

remove debris and pathogens

dendritic cells and macrophages

present antigens they engulf

natural killer cells

recognize certain types of abnormal antigens presented by cells infected by viruses, or by abnormal cells, destruction of infected cell

immunological surveillance

destroys abnormal cells

nonspecific response - fever

increase in body temperature, caused by pyrogens, increases metabolism to speed up immune response, a natural response to infection

pyrogens

proteins released during phagocytosis, results in brain "resetting body's thermostat"

specific defenses

target a single pathogen and result in future protection (immunity)

possibility 1

pathogen enters extracellular space and gets sucked into lymph vessels, then travels to lymph nodes and can interact with B cells

possibility 2

pathogen is engulfed by macrophages at the site of injury. macrophages are cleaning up debris from damage

possibility 3

pathogens "trick" our cells and gain entry into cytoplasm. can then use cells to make more pathogens - infected cells

cell-mediated immunity

antigen-presenting infected cells activate and are killed by cytotoxic T-cells

antibody-mediated immunity

antigens activate the production of antibodies by B-cells

helper T-cells

required for cell- and antibody- mediated immunity

helper T-cells

activated by "professional" antigen-presenting cells such as dendritic cells and macrophages

step 1

antigen presentation

antigen presentation

both infected cells and the "professional" antigen-presenting cells "show" or "present" antigens to cells of the immune system (T cells)

2 types of MHC proteins

class I and class II, although both classes present antigens, they use different proteins that affect the type of cell that can recognize the antigen

MHC

major histocompatibility complex

MHC

family of protein complexes specialized for presenting antigens

MHC class I

found on all nucleated cells

MHC class II

found on antigen-presenting cells (APCs)

"professional" APCs

macrophages, dendritic cells - engulf foreign antigens in the body and present them (not infected)

when class II cells present an antigen,

sends a message to destroy, the cell is not infected, but functions to display engulfed antigens

MHC class II are only recognized by

helper T-cells, activates helper T-cells for the specific antigen, required for all other steps of the immune system

MHC class I cells

present antigens when they have become infected

when class I cells present a foreign antigen,

send a message that they are infected

MHC class I cells are recognized by

cytotoxic T cells

cytotoxic T cells

activated to kill cells displaying a specific antigen, infected cells are targeted for destruction

step 2

activation of helper T cells, required to activated ALL immune responses

inactive T (helper) cell

binds antigen presented by class II cells

activated T cell

divides, secretes cytokines

cytokines

small proteins that cause changes in many cell types

cytokines functions

help stimulate Tc cells and B cells, non-specific responses

activation

causes differentiation of memory Th cells

memory Th cells

stored in lymph nodes, faster response with next encounter of same antigen

step 3

activated of cytotoxic cells (Tc)

Tc cells activation

initiates cell-mediated immunity, starts with inactive Tc cell

inactive Tc cell

binds antigen presented by class I cell, further activated by cytokines

activated Tc

divides to create specific army of cells

activated Tc cells

attack infected cells with same presented antigen, causes differentiation of memory Tc cells

step 4

B cell activation

B cells

have antibody receptors for specific antigens on cell surface

sensitization

receptor binds antigen, engulfs, and presents on MHC II

activation

bind Th cell activated with same antigen "co-stimulation", required step

produce plasma cells

make and secrete antibodies

produce memory B cells

faster response if exposed to antigen again

neutralization of antibodies

bind to part of antigen that is toxic

agglutination

antibodies bind to multiple antigens causing them to stick together and prevents transport throughout body

additional mode of action (antibodies)

precipitation of antigens from body fluids

recap

- specific response occurs in lymph nodes

- immunity creates a memory of disease

- vaccines also generate immunological immunity