3 Microbiology: The Immune System

Question 1

from birth onwards, how often are both animals and humans exposed to bacteria, viruses, fungi, protozoa, and multicellular parasites?

Answer 1

Constantly

Question 2

What is the immune system?

Answer 2

a complex array of defensive measures evolved from vertebrates to combat invaders and altered host cells.

Question 3

How do the different elements of the immune system interact and communicate?

Answer 3

communicate via soluble molecules (CYTOKINES) and by direct CELL-TO-CELL interaction
these interactions provide the mechanisms for activation and control of the protective responses

Question 4

How does disease occur even with the immune system?

Answer 4

the protective responses to some infectious agents are insufficient
the response to the invader may be excessive

Question 5

How are immune responses mediated?

Answer 5

by a variety of cells with defined functions and by the soluble molecules which they secrete

Question 6

Where are ALL blood cells generated from?

Answer 6

from a common stem cell in the bone marrow, called PLURIPOTENT stem cells (blood-forming)
ALL blood cells have limited life-spans and produced throughout the life of the animal

Question 7

what are erythrocytes?

Answer 7

red blood cells

they remain within the blood vessels and transport oxygen and carbon dioxide bound to hemoglobin

Question 8

What are leukocytes?

Answer 8

white blood cells

they are the migratory cells of the body’s protective system

Question 9

What are thrombocytes?

Answer 9

platelets
are not entire cells but small detached cell fragments or “minicells” derived from the cortical cytoplasm of large cells called MEGAKARYOCYTES.
blood contains large numbers, and they adhere to the endothelial cell lining of damaged blood vessel, where they help repair breaches and aid in the process of clotting.

Question 10

what is hematopoiesis?

Answer 10

is the formation and development of red and white blood cells from pluripotent stem cells (PPSC; ability to differentiate along a number of pathways) in the bone maarrow

Question 11

Why are stem cells few in number and maintained at homeostatic levels throughout life?

Answer 11

there is only one stem cell per 100,000 bone marrow cells, and they are maintained at this level because of their capasity for self-renewal.
when there is an increased demand for hematopoiesis, stem cells display an enormous proliferative capasity

Question 12

Early in hematopoiesis, a PPSC differentiates along one of two pathways giving rise to what two different cells?

Answer 12

a lymphoid stem cell or a myeloid stem cell.
These cells differentiate into PROGENITOR cells which have lost capacity for self-renewal and are committed to a given cell lineage.

Question 13

What does the lymphoid stem cells generate?

Answer 13

generate T and B progenitor lymphocytes and natural killer cells (NKC)

Question 14

What does the myeloid stem cell generate?

Answer 14

generates progenitor cells for red blood cells, the various white blood cells, mast cells, and platelets (from megakaryocyte).

Question 15

What regulates the growth and differentiation of lymphoid and myeloid stem cells?

Answer 15

regulated by growth factors or CYTOKINES (low molecular weight glycoproteins) secreted by bone marrow stromal cells (connective tissue cells), macrophages, T lymphocytes, etc.

Question 16

How do white blood cells function and transport? (A local injury or infection?)

Answer 16

most function in tissues other than the blood, the blood supply transports them to where they are needed.
infection/injury- rapidly attracts WBCs into the affected region as part of the inflammatory response, which helps fight the infection or heal the wound.
Each type of WBC has its own role in host defense

Question 17

what are the three different ways WBCs can be classified?

Answer 17

shape of nucleus
presence or absence of cytoplasmic granules
type of defense function

Question 18

What are granulocytes?

Answer 18

category of WBCs
all contain numerous lysosomes and granules and are subdivided into three classes on the basis of the morphology and staining properties

Question 19

what are the three classes of granulocytes?

Answer 19

neutrophils
basophils
eosinophils

Question 20

what are properties of neutrophils?

Answer 20

do not pick up either stain (acidic or basic) very well so they show up colorless on stained blood smears
contain lysosomal enzymes (digestive enzymes) that aid in killing microorganisms that it has engulfed (PHAGOCYTOSIS)
site of action is in tissues
polymorphonuclear

Question 21

what are properties of basophils?

Answer 21

they pick up the basic stain and appear blue
contain HISTIMINE that help mediate the inflammatory response
site of action is in tissues
polymorphonuclear

Question 22

what are properties of eosinophils?

Answer 22

pick up the acidic stain and appear red
modulate allergic reactions, DESTROY some PARASITES, PHAGOCYTOSIS
site of action is in tissues
polymorphonuclear

Question 23

what happens as a granulocyte matures?

Answer 23

its nucleus transform from a round structure to a segmented structure that takes on many shapes (polymorphonuclear).
thin filaments of chromatin connect these segments

Question 24

what are agranulocytes?

Answer 24

are WBCs that do not have specific staining granules in their cytoplasm.
NO GRANULES

Question 25

What are included in the agranulocytes?

Answer 25

Monocytes (macrophages)

Lymphocytes (B & T)

Question 26

what are the properties of Monocyte (macrophages)?

Answer 26

PHAGOCYTOSIS, ANTIGEN processing
site of action is blood or body tissues
no staining granules
mononuclear

Question 27

what are the properties of B lymphocytes?

Answer 27

ANTIBODY PRODUCTION (humoral immunity)
site of action is lymphoid tissue
no staining granules
mononuclear

Question 28

what are the properties of T lymphocytes?

Answer 28

CELL-MEDIATED IMMUNITY, LYMPHOKINE production
site of action is lymphoid tissue and other body tissue
no staining granules
mononuclear

Question 29

What is the total WBC count used for?

Answer 29

to evaluate a patient for the diagnosis or prognosis of an abnormal condition.
Ex. if an infection is present in the body, there will be an increased need for neutrophils to kill the microorganisms. The bone marrow responds to this need by releasing more neutrophils into the blood stream that will travel to the tissue where the infection is located.

Question 30

The total WBC count is equal to what?

Answer 30

equal to the sum of each of the individuals WBC counts.
Ex:
if one cell type increases or decreases the total WBC count increases or decreases
however if one cell type increases and another cell type decreases the net effect could be a normal total WBC count.

Question 31

what is leukocytosis?

Answer 31

Increase in the number of circulating white blood cells

Question 32

what is leukopenia?

Answer 32

decrease in the number of circulating white blood cells

Question 33

what is the purpose of hematocrit?

Answer 33

Used for blood testing
blood is place in a plugged test tubed and then spun
after spinning layers should be present showing plasma, WBCs and platelets (buffy coat), and red blood cells.
with the levels shown one can determine anemia (low red blood cells) leukocytosis (thick buffy coat) polycythemia (high red blood cells) leukopenia (thinner buffy coat) and of course normal.

Question 34

What is the difference between plasma and serum?

Answer 34

Plasma- with clotting factors (collected with anticoagulant)

serum- no clotting factors

Question 35

When are domestic animals and humans generally free of microorganisms?

Answer 35

in utero