2- Cells of the Immune System

Question 1

Hematopoietic Stem Cells (HSC)

Answer 1

Progenitor cells from which all differentiated blood cell types arise during the process of hematopoiesis.

Though they can be found in the circulation, they generally home in the bone marrow or in specific niches.

Question 2

How do Hematopoietic stem cells self renew?

Answer 2

They must be surrounded by a niche of osteoblasts and sinusoidal endothelial cells because these supply GROWTH FACTORS AND OTHER REGULATORY MOLECULES that support HSC self-renewal.

Question 3

HSC differentiation

Answer 3

Influenced by STROMAL CELL FACTORS.

These push the cells to be differentiated into COMMON LYMPHOID or MYELOID PROGENITORS and then eventually many different cell types (ex. replenishment of RBC, WBC and platelets)

Question 4

Basic Lymphocyte Functioning

Answer 4

These are responsible for setting up specific responses to pathogens. It only works if these lymphocytes first LOOK FOR THE PATHOGENS.

In lymph nodes, lymphocytes are presented with broken parts of pathogens.

Question 5

Where do lymphocytes typically meet their specific pathogens?

Answer 5

(1) lymph nodes
(2) mucosal lymphoid tissue such as in the intestine
(3) spleen
(4) tonsils and adenoids

Question 6

Interconnection between innate and adaptive system.

Answer 6

Innate cells are responsible for presenting suspected pathogens to the adaptive cells.

Question 7

Myeloid White Blood Cells

Answer 7

• comprise most of the innate immune cells

- first line of defense against microbial invasion

Question 8

Basics of the Neutrophil

Answer 8

(1) Aka the PMN
(2) FUNCTION: Phagocytosis and activation of bactericidal mechanisms. Foot soldiers of the immune system. Most numerous and short lived.

Most abundant WBCs.

Question 9

What forms pus?

Answer 9

Ultimately it is a result of neutrophil activation. The majority of pus’s content are dead neutrophils.

Question 10

Basics of the Monocyte/Macrophage

Answer 10

FUNCTION: Phagocytosis and activation of bactericidal mechanisms

Also function in antigen presentation and recognition of foreign microbials

Monocytes REPLENISH tissue macrophages and dendritic cells.

Macrophages are the work horses of the adaptive immune response

Question 11

Antigen

Answer 11

Any molecule that can bind to an antibody

Question 12

Basics of the Dendritic Cell

Answer 12

FUNCTION: Antigen uptake in peripheral sites. Antigen presentation to naïve T-cells (within lymph node), signaling them to proliferate and attack.

Play a KEY ROLE in initiating adaptive immunity.

They degrade pathogens for the purpose of DISPLAY rather than destruction.

Question 13

Basics of the Eosinophil

Answer 13

FUNCTION: Killing of antibody-coated parasites

Activated eosinophils release highly dangerous substances from their granules which are toxic to parasites AND to surrounding tissue.

They are also recruited in allergic reactions and can help sustain them, sometimes causing remodeling of the tissues.

Question 14

Basics of the Mast Cell

Answer 14

FUNCTION: Release of granules containing histamine and active agents.

Activation causes degranulation and increases local blood flow to allow recruitment of WBC, as well as increased fluid accumulation to flush antigen to the lymph.

MOST ASSOCIATED WITH ALLERGIC REACTIONS.

Question 15

Basics of the Basophil

Answer 15

FUNCTION: Participates in immunity against parasitic infection and in allergic response, along with mast cells and eosinophils

Question 16

Basics of the NK cells

Answer 16

Natural Killer Cells

FUNCTION: Release of lytic granules that kill some virus-infected cells.

Part of innate immunity.

They recognize when cells “don’t look right” and prevent a viral infection from “going viral” by inducing apoptosis.

Question 17

Basics of the B-cells

Answer 17

Have surface B-cell receptors that are variant and recognize a specific antigen. Proliferate and differentiate into PLASMA CELLS.

Question 18

Plasma Cells

Answer 18

Effector form of B-cells

Produce antibodies which bind specific antigen.

Question 19

Basics of the T-cells

Answer 19

Have surface T-cells receptors that are variant. After the first encounter with its antigen it proliferates and differentiates.

Can include cytotoxic T-cells which can directly kill infected cells.

Question 20

The 2 major forms of T-cells

Answer 20

(1) Cytotoxic: recognize and kill viral-infected cells (CD8+)
(2) Helper T cells: direct the immune response by macrophages and B-cells and augment recruitment of immune cells to the infection site (CD4+)