Immune System Cell Types

Memorize what does what, not meant to teach the entire unit, just the categories of cells.

Megakaryocytes

Reside in the bone marrow, break down into platelets.

Platelets

Break off of megakaryocytes and flow through bloodstream. Play key role in blood clotting by forming plugs at sites of vessel injury and support immune response by releasing signaling molecules and interacting with white blood cells.

Erythrocytes (red blood cells)

Circulation of gases in blood and formation of blood clot (trapped by fibrin).

Granulocytes

Umbrella term for eosinophil basophil, mast cells, and neutrophils because they all appear granular due to the large number of secretory vesicles on their surface.

What is similar about how Eiosinophils, Basophils, and Neutrophils function?

They all circulate through the blood stream until they detect a pathogen.

What are the three granulocytes that circulate through the blood? Describe the response of each once they detect a pathogen.

Eiosinophils: Secrete cytotoxic agents and cytokines.

Basophils: Secrete cytotoxic agents, cytokines, and histamine.

Neutrophils: Engage in phagocytosis and can also secrete cytokines.

What are cytokine molecules

Generic term for molecules that influence the behavior of neighboring cells.

When granulocyte doesn’t circulate through the bloodstream? Where does it reside and what function does it perform?

Mast cells: reside in interstitial fluid and release histamine in response to many innate system triggers.

Monocytes: Location and function?

Circulate through the blood and penetrate into tissues when detect signal of damage. Once they penetrate into tissues, they differentiate into macrophages.

Macrophages: Location and function

Originate from monocytes once they penetrate tissues in response to damage signals. Engulf and destroy foreign particles by phagocytosis.

Natural Killer Cells function?

Secrete antimicrobial and cytotoxic agents (they are not specific to any particular pathogen, therefore still part of the innate immune system).

B cells function?

Produce antibodies. These include memory and plasma cells.

Helper T Cell function?

Stimulate B cells

Cytotoxic T Cell function?

Secrete Cytotoxic agents

Adaptive Immunity is only found in _______

Vertebrates

Which branch of the immune system is responsible for Inflammatory response?

Innate Immune System

Which branch of the immune system is responsible for specificity and memory?

Adaptive Immune System

Which branch of the immune system is responsible for surface coverage and barriers to infection?

Innate Immune System

Which branch of the immune system is responsible for nonspecific, rapid response?

Innate Immune System

Which three things contribute to the body’s skin coverage and barriers to infection?

Skin, mucous membranes, and digestive substances

How does the skin contribute to the body’s skin coverage and barriers to infection?

Physical barrier, dry & dead cellular layer. Low pH environment is unideal for growth of most bacteria.

Lysozymes function?

Break down "chew up” bacteria

How do mucous membranes contribute to the body’s skin coverage and barriers to infection?

Traps foreign particles, contains lysozymes that break down bacteria, and sometimes contains cilia that move particles out of the body. Found in airways, digestive system, and reproductive tract.

How do digestive substances contribute to the body’s skin coverage and barriers to infection?

Stomach acid, enzymes

What must the innate immune system do in order to target pathogens? How does it do this?

It must distinguish between “self” and “non-self,” and does this via Pathogen Recognition Receptors (PRRs) on the surface of immune cells that recognize distinct Pathogen Associated Molecular Pathogens (PAMPs).

Neutrophil location and function?

Phagocytes that reside in blood until detect pathogen, then move into tissues.

Main differences between macrophages and neutrophils?

Neutrophils circulate through bloodstream and only penetrate into tissues once detecting a pathogen while macrophages reside in tissues (they only become macrophages once monocytes penetrate into the tissue).

What triggers phagocytosis?

Binding of PRR on the surface of a phagocytic cell to a PAMP.

Pseudopodia

Extensions of phagocytic cells that “grab” foreign particles to be engulfed.

What role to lysosomes play in phagocytosis?

Fuse with phagosome and kill pathogen using enzymes.

Which types of cells are considered “executioner cells”?

Eosinophils, basophils, and natural killer cells.

How to “executioner cells” kill pathogens?

PRR binds to PAMP trigger intracellular signaling pathway —> cytotoxic compounds stored in the immune cell’s vesicles is released to kill the pathogen.

Which cells are involved in the inflammatory response? What do they do?

Mast cells and macrophages secrete substances (cytokines, histamines) that cause vasodilation at local arteries to increase blood flow and bring more immune cells, increase blood vessel permeability for movement of immune cells into tissues, and attract other immune system cells (chemokines).

What are chemotaxis

chemical trails that lead cells to the infectious agent or to other immune cells.

Extravasion

The process of neutrophils, monocytes, and other leukocytes into tissues through spaces between cells of vessel walls. Done by following chemotaxis (chemical trail) to the source.

Steps of Extravasion of a cell

1. Tether- Cell catches on the vessel wall

2. Rolling- Cell continues rolling along wall with blood flow.

3. Activation of Adhesion - Cell secretes adhesion molecule

4. Diapedesis -

5. Traversing Basal Lambia

6. Migration though ECM -

Antigen

Piece of foreign material used by the immune system to recognize invaders.

What must the adaptive immune system do to recognize pathogens? How does this process differ from the innate immune system?

It must distinguish between “self” and “non-self.” Distinct MHC markers are found on all nucleated cells in invertebrates, allowing the recognition of self. Infected cells and some macrophages present antigens on the surface of their own cell membrane in combination with MHC molecules for activation of the adaptive immune response.

Major Histocompatibility Complex (MHC)

Found on the surface of all nucleated cells in vertebrates. Allows cells to recognize “self.”

MHC I

Binds to CD4 Receptor on Helper T cells to activate them.

MHC II

Binds to CD8 Receptor on Cytotoxic T cells to activate them.

What do B cells do?

Produce antibodies that recognize antigens, and either present them on the cell surface or secrete them.

Describe the structure of an antibody.

Y-shaped, with the top variable region that specifies which antigen will be recognized and the bottom constant region that only varies between major classes of antibodies.

What do antigens do?

Recognize antigens.

What are the two ways a B cell may be activated?

1. Foreign cell is engulfed by phagocytosis and antigens are presented on the cell surface by MHC molecules. TCR on helper T cell binds to presented antigen, activating the T cell. Activated helper T cell finds B cell that produces appropriate antibody and antidotes it using cytokines.

2. Antibody on surface of B cell binds to antigen, activating the B cell.

What do B cells do once activated?

Divides by mitosis to produce many plasma cells and memory B cells. These will secrete and present antibodies.

Plasma B cells vs. Memory B cells?

Plasma B cells secrete the antibody of the original activated B cell, while memory B cells present the antibody of the original activated B cell.

Opsonins

Proteins that coat pathogens and mark them for phagocytosis

Epitope

The specific molecular structure of the antigen that is bound by the antibody.

How do antibodies block infection? What can you say they act as?

Act as opsonins, coatings virus, which cannot tell its been coated, the virus is then destroyed.

How does adaptive response change between first and second exposure to an antigen.

Response by the adaptive immune system is faster and larger the second time it encounters a specific antigen. This serves as the basis for vaccines.

Chimeric Antigen Receptor (CAR)

Used to treat blood cancer (leukemia); works via removing a person’s T cells and giving them receptors that can recognize the antigens on the surface of the cancer cells.

Primary vs secondary lymphoid tissues

Primary tissues are where the lymphocytes are produced, while secondary tissues are where they are great in population but are not actively produced.

Which parts of the body are considered primary lymphoid tissues?

Bone marrow, Thymus.

Which parts of the body are considered secondary lymphoid tissues?

Spleen, lymph nodes/lymph vessels/tonsils, Peyer’s Patches.

What are the two important roles of the Thymus?

1. This is where selection and elimination of cells that recognize self “too strongly” occurs (this can lead to autoimmune disorders).

2. This is where T cells differentiate into cytotoxic or helper T cells.

What is the main role of the lymph nodes?

Filter lymph. Hub for monitoring infection, this is the place where antigens may be presented.

Main roll of Spleen and its immune cell inhabitants?

Filters blood. Macrophages, natural killer cells, B and T cells.

Peyer’s Patches main role and cell inhabitants?

Monitors gut microbiome. Mainly B cells, but also T cells macrophages, basophils, eosinophils, and mast cells.

What do the tonsils do to assist in protecting the body from pathogens?

Responds to inhaled antigens.