21 & 22 Lymphatic and Immune System

Question 1

What are the two primary lymphatic organs?

Answer 1

Red bone marrow
Thymus

Question 2

What are lymphatic capillaries missing that blood capillaries have?

Answer 2

lymphatic capillaries are missing a basement membrane

Question 3

What are the two types of pulp in the spleen? State their function.

Answer 3

Red pulp - contains erythrocytes, platelets, macrophages and B-lymphocytes, serves as a blood reservoir for both erythrocytes and platelets
White pulp - clusters of T-lymphocytes, B-lymphocytes and macrophages surrounding a central artery, monitors the blood for foreign materials, bacteria, other harmful substances

Question 4

What are some of the benefits of a fever?

Answer 4

-inhibits the reproduction of bacteria and viruses
-promotes interferon activity
-increases activity of adaptive immunity
-accelerates tissue repair
-additional immune cells migrating out of blood.

Question 5

Name and define three processes that occur during inflammation that help leukocytes locate damaged tissue.

Answer 5

1)release of chemicals by injured tissue causes endothelial cells of nearby capillaries to display adhesion molecules that attract neutrophils and proinflammatory chemicals cause neutrophil CAM (cell adhesion molecules) to stick to endothelial cells (margination)
3) inflammatory mediators cause mast cells to release histamine, increasing capillary permeability and allowing for diapedesis
chemicals released from damages cells, dead cells or pathogens diffuse and forma chemical gradient that attracts immune cells (chemotaxis)

Question 6

Lymphocytes go through two rounds of selection before they are activated. For each round what is selected and which cells survive?

Answer 6

Positive Selection→ if cell can bind to MHC it survives, CD4 or CD8 receptor complex must be able to mind to an MHC class I or II molecule on a thymic epithelial cell
Negative selection → if cell can bind self antigen it is killed, TCR must not bind to self antigen within MHC molecules presented by a thymic dendritic cell, self-tolerance

Question 7

All nucleated cells can present antigens, but some cells do it as part of their major function. Which cells are your “professional” antigen presenters? What molecule is necessary for antigen presentation?

Answer 7

–>dendritic cells and macrophages (also B-lymphocytes)
–>MHC transmembrane protein is required for presentation (MHC class I on all nucleated cells and both class I and II on APCs)

Question 8

Helper T Lymphocyte activation

Answer 8

1) CD4 receptor binds to the MHC class II molecule (TCR interacts with the antigen to recognize it)
2) second signal - other receptors of each cell interact to release cytokines (IL-2)
3) proliferate/ differentiate to form clones (active and memory helper Ts)

Question 9

Cytotoxic T lymphocyte activations

Answer 9

1) CD8 binds to MHC class I molecule of the infected cell (TCR interacts with antigen to recognize it)
2) other receptors of each cell interact creating second signal, enhanced by IL-2 from helper Ts
3) proliferate/differentiate to form clones (active and memory cytotoxic Ts)

Question 10

B lymphocyte activation

Answer 10

1) antigen binds to BCR, B-lymphocytes engulfs and presents antigen to helper-T
2) other receptors of the B-lymphocyte and helper T interact and helper T releases IL-4
3)IL-4 stimulates B-lymphocyte to proliferate and differentiate (plasma cells producing antibodies and memory B-lymphocytes)