BIOL 252 Portage Module 4: Lymphatic System and Immunity

Lymphatic System

lymph, lymphatic vessels, lymphoid tissue, and organs.

Function of lymphatic system

take up excess fluid and retun it to bloodstream

lymph

excess fluid not returned to cv system

lymphatic capillaries

returns lymph to the heart by means other than the cv system

Where are there no lymph vessels?

bone marrow and epidermis

Lymph nodes

found at lymphatic junctions

filter debris and infectious materials from entering

What is the function of the spleen regarding blood cells?

Extracts old blood cells and platelets

What does the spleen remove from the blood?

Debris, foreign material, toxins, bacteria, and viruses

What types of immune cells are contained in the spleen?

Lymphocytes and macrophages

thymus

anterior surface of the heart

secretes thymosin and thymopoeitin that enable T cells to mature

T Cells

attack pathogenic cells

Tonsils

lateral, posterior throat

gather bacteria that is inhaled or from food

Appendix

tube connected to the cecum (end of large intestine)

stores beneficial gut bacteria

Red Bone marrow

site of T/B cell development

B cells remain to mature

Peyer's Patch

MALT (mucosa-associated lymphoid tissue) clusters in intestines

containt WBC's

What is the first line of defense in the nonspecific immune system?

Physical and chemical barriers

What is the second line of defense in the nonspecific immune system?

Destroys pathogens that have already entered the body

How does the nonspecific immune system respond to threats?

It has the same response to all threats, which is to destroy pathogens and act rapidly

specific immune system (adaptive)

several days to activate

targeted, effective against pathogens

main responders are T/B cells, antibodies, and antigen-presenting cells

What is the function of a phagocyte?

Surround and engulf particles (phagocytosis) to clean or kill cells.

What role do phagocytes play in the immune system?

They are a fast-acting first line defense for cells that have entered the body.

macrophage

irregularly shaped phagocyte

agranulocytes

move through tissues/into capillaries

participated in innate and adaptive respoinses

Kupffer Cells

liver macrophages

histiocytes

Macrophages in connective tissue

Alveolar macrophages

lungs

Monocyte

differentiates into macrophage or dendritic cells

neutrophil

phagocytic cell attracted via chemotaxis to infected tissue from bloodstream

What is diapedesis?

WBC's move through endothelial walls to reach inflammation sites/infections.

What do granulocytes do?

Engulf and destroy pathogens, while releasing chemicals from granules to kill.

NK Cells

lymphocytes and induce lysis in infected cells

What is the first step in NK cell death?

Recognize infected cell and adhere to it

What happens after NK cells recognize and adhere to an infected cell?

Reallign Golgi to face infected cell and secrete perforins

What do perforins do in the context of NK cell death?

Form pores for granzymes to enter through

What is the final step in NK cell death?

Lysis of the infected cell

Cardinal signs of inflammation

heat, swelling, redness, and pain

Cytokine

signaling molecule for cells over short distances

Secreted in Intracellular spaces

Chemokine

attracts cells over long distances

cell migration

Histamine

vasodilator

increases blood flow

increase capillary permeability, causing plasma to leak which increases swelling

Heparin

anticoagulant

mediate inflammatory chemicals released

Leukotrienes

attract neutrophils via chemotaxis

increase vascular permeability

Prostaglandins

vasodilation by relaxing smooth muscles

major cause of pain

What initiates the inflammatory response?

Tissue injury: injured cells release chemicals that stimulate mast cells to release inflammatory mediators.

What role do histamine and heparin play in the inflammatory response?

They cause vasodilation, leading to increased blood flow, which is responsible for heat and redness.

What is the effect of increased vascular permeability during inflammation?

It causes leakage of fluid into the interstitial space, resulting in swelling (edema) and pain.

What attracts neutrophils to the site of inflammation?

Leukotrienes attract neutrophils.

What is the role of macrophages in the inflammatory response?

Macrophages clean up debris from the site of injury.

What can result from severe inflammation involving phagocyte recruitment?

The formation of pus, which consists of cell remains.

Complement System

proteins in blood plasma

made in the liver

What is the function of opsonization in the immune response?

Bind to cell of pathogen and label it for phagocytosis.

What is chemotaxis in the context of the immune response?

Attract other phagocytes to the site of infection.

What is the role of the Membrane-attack complex (MAC) in the immune system?

Inserts pores into the plasma membrane of pathogens, causing lysis by disrupting osmotic balance.

What is activated in the alternate pathway when interacting with foreign materials?

C3

What happens to C3 when it reacts with plasma?

It splits apart.

What does the larger fragment C3b do?

It binds to the pathogen surface.

What is the role of the smaller fragment C3a?

It leaves and attracts phagocytes.

What does C3b activate in the immune response?

MAC with C5-C9.

What is the function of C3b in relation to pathogens?

It marks them for phagocytosis.

What is the classical pathway in the immune system dependent on?

Antigens and the adaptive immune response

How many antibodies must C1 attach to in order to activate in the classical pathway?

Two antibodies

What role does C1 play in the classical pathway?

C1 acts as an enzyme, splitting C3 into C3a and C3b

cytokines

proteins that regulate/signal specific and nonspecific responses

types of cytokines

interferons: inhibit replication, activate NK cells

alpha: prodices by infected cells, attracted NK cells

beta: secreted with fibroblasts, slow inflammation

gamma: secreted by T cells and NK cells to stim macrophages

Interleukins

chemical activates, increase immune response

Pyrogens

type of interleukin

raise body temp in hypothalamus to create a fever

Why are fevers beneficial?

interfere with growth/replication of pathogens

casue lysosomes to break down

promote WBC metabolism

What is an antigen?

A substance that can be recognized by the immune system.

What can antigens bind with?

Specific antibodies or antigen receptors on immune cells.

What types of entities can be considered antigens?

Pathogens, toxins, and cancer cells.

Antibody

Y-shaped protein

can recognize, bind to, and neutralize antigens

What is a complete antigen?

A substance that can trigger an immune response and react with the products of that response (T cells and antibodies).

What are complete antigens typically composed of?

Large, complex proteins.

Haptens

small molecules that can induce immune responses, but only when they bind to larger proteins

What is an antigenic determinant?

A small region in an antigen that an antibody can bind to.

What is the size limitation of an antigenic determinant?

It consists of six or fewer amino acid residues or 1-2 sugars from a carbohydrate.

Carbohydrate antigen

bacterial cell walls and RBCs

more simple

Protein Antigen

Respond to parasites and viruses

3-D shaped

more complex

Self-antigens

antigens that present in bodys own cells

proteins, carbohydrates, nucleic acids, lipids

immune system recognizes them as "safe" and does not harm them

Major Histocompatibility Complex (MHC)

cluster of genes that encode antigen-presenting molecules on cell surfaces

Antigen presentation

Process of displaying antigens to T cells.

Where are Class I MHC proteins found?

On the membrane of all nucleated cells

What do body cells do with small peptides in relation to Class I MHC proteins?

They gather small peptides and present them on the surface as a signal for immune cells

What do T cells do if they recognize a healthy cell?

They ignore the cell

What happens when T cells recognize an abnormal peptide?

They attack the cell

Where are Class II MHC proteins found?

Only in membranes of immune system cells, specifically on APCs.

What do Class II MHC proteins contain?

Antigenic fragments from antigen processing of pathogens.

What happens to antigen fragments in relation to Class II MHC?

Antigen fragments bind to Class II MHC and enter the membrane.

What is the role of APCs in relation to T cells?

APCs use protein-antigen to activate T cells.

Antigen-presenting cells (APC's)

cells that present antigens to other cells

"professional" APC's activate T cells

Phagocytes

Three types of APC's

Macrophages: mucousal surfaces

Dendritic: WBC's

B cells

Lymphocytes

T and B cells

primary cells controlling immune responses

Where do T Cells develop?

Thymus

What do T Cells control?

B cell immune responses

Where do mature T Cells migrate after entering the bloodstream?

Lymph nodes, spleen, and lymphoid tissue

B Cells

Develop in bone marrow

antibody-mediated immunity, can differentiate into plasma cells

Central Tolerance

destruction of B cells that recognize self-antigens in bone marrow

clonal deletion

immature B cells that bind to self-antigens undergo apoptosis

What is peripheral tolerance in the context of B cells?

Functional B cells leave the bone marrow but haven't been exposed to antigens in peripheral tissue, remaining inactive.

What type of MHC proteins do professional antigen-presenting cells (APCs) express?

Class I and class II MHC proteins.

What are plasma cells?

B cells that differentiate after binding to an antigen.

Where do plasma cells migrate after differentiation?

They migrate back to the bone marrow.

What happens to some plasma cells after they create antibodies?

Some die while creating antibodies.