Which organs of the immune system are classified as "primary immune organs"?
The thymus and bone marrow. All of the rest are secondary.
What distinguishes primary immune organs from secondary immune organs?
Immune cells originate and mature in primary immune organs and have the capacity to interact with an immunogen upon leaving.
Where is bone marrow found?
- 1.) Long bones (legs, arms, fingers, toes)
- 2.) Flat bones (cranium, pelvic bone, sternum, scapula, ribs)
- In short, bone marrow is all over the body.
What is the function of bone marrow? Why must it continue to work throughout an individual's entire life?
- 1.) It makes all blood cells and some mast cells
- 2.) Cells that mature in the bone marrow have a short life span
For example: B-cells (3-7 days), neuts. (1 day), eosins. (1 day), macrophages (25-30 days).
What are the functions of the Thymus gland?
- 1.) It is the principle site of pre-T-cell maturation to T-helper cells
- 2.) It is the principle center for self-recognition (during the 8th to 9th week of embryonic development)
True or False?
Even if a virus is present in a fetus during weeks 8 and 9, the body will eventually recognize the pathogen as foreign and respond accordingly.
- Though the mother's immune system will handle it at that time, for some time after birth the child's body will not respond to the pathogen.
True or False?
Though a child's body may have accidentally labeled a pathogen as "self" during fetal development, given enough time, the body may respond appropriately if re-exposed.
- Self-recognition is a memory type activity. If the child is not re-exposed to the pathogen for many years (ex. 15), the body will have forgetten it as "self" and will attack it.
True or False?
The thymus gland does not function for an entire lifetime.
- The thymus gland atrophies over several decades and ultimately stops functioning, beginning at puberty due to hormonal changes (sex steroids, cortisol, etc.)
All things being equal, a woman who has relatively more pregnancies than normal will have (less, more) atrophy of her thymus.
During what decade(s) of life is it expected that the thymus gland nearly ceases to function?
60's - 80's.
Given that the thymus gland nearly ceases to function in the latter years of life, why do people continue to live so long?
No one kno
ws for sure.
Evidence shows that mice may have structures in their intestines similar to a thymus. Pre-T-cells go in, come out as mature T-cells.
A Pre-T-cell may come out of the thymus as ...?
- 1.) A T-helper cell (TH0)
- 2.) A CTL
- 3.) A T-regulatory cell
If the body is suffering from a viral infection, which WBC level should you be concerned with being too low?
- Neutrophil count.
- Phagocytosis doesn't stop during an immune response, and neutrophils die once they have "eaten" a microbe/molecule.
List the 5 secondary immune organs discussed in class.
- 1.) Spleen
- 2.) Lymph nodes
- 3.) Adnoids and Tonsils (MALT)
- 4.) Appendix (MALT)
- 5.) Peyer's patches (MALT)
What 5 characteristics distinguish secondary immune organs?
- 1.) Immune cells are concentrated here
- 2.) Site of interaction with immunogens
- 3.) Site of activation/proliferation/ and differentiation into needed cell-type
- 4.) Immune cells are relocated to different place in organ
- 5.) Organs function as filters
The spleen filters _________ for the presence of foreign organisms, while the lymph nodes filter _________.
- 1.) The vasculature
- 2.) Interstitial fluid
*Criteria of an immunogen: If an organism cannot be phagocytized (and thus no IDP), how must we deal with it?
Where is the spleen located?
On the left side of the body, posterior to the stomach. It is encased in a capsule.
How many basic tissues make up the spleen? What are they?
- 1.) 2 distinct types of tissue
- 2.) Red pulp and white pulp
What are the functions of the spleen?
- 1.) Stores excess erythrocytes (ready as an immediate source of healthy RBC's)
- 2.) Repairs RBC's
- 3.) Principle center of antibody production
- 4.) Screens vasculature for foreign organisms and transformed cells
What specialized tissue allows the spleen to act as a filter?
Reticular connective tissue.
What is the function of the white pulp of the spleen?
White pulp contains a high concentration of immune cells and is the site of their activation and proliferation.
What term describes "scaffolding of dense connective tissue" that provides structure to the spleen?
Starting with the descending aorta, describe the breakdown of blood vessels up to and inside the spleen.
- 1.) Descending aorta
- 2.) Celiac trunk
- 3.) Splenic artery
- 4.) Trabecular arteries
- 5.) Central arteries through tubes of white pulp and opening into red pulp
What structure/material surrounds the central arteries of the spleen? What cell(s) reside there?
- 1.) The periarterial lymphatic sheath (PALS)
- 2.) T-helper cells
What cells reside in the reticular connective tissue of the white pulp?
At various points along a tube of white pulp are follicles. What cells reside here?
- 1.) Dendritic cells
- 2.) B-cells
In a follicle, B-cells and dendritic cells concentrate in the _______. Acitivated B-cells & T-cells proliferate in the _______.
- 1.) Mantle layer
- 2.) Germinal center
In the white pulp of the spleen, where do macrophages concentrate?
In the outer layer of the follicles, known as the marginal layer.
What WBC's are present in the white pulp of the spleen?
- 1.) Dendritic cells
- 2.) Macrophages
- 3.) B-cells
- 4.) T-helper cells