PCAT-IMMUNE SYSTEM |VERIFIED QUESTIONS AND CORRECT
DETAILED ANSWERS|RATED AND GRADED A+ NEW UPDATE|
2026/2027
All blood cells arise from stem cell precursors located where? - ANSWER✔ bone marrow
The first line of defense in human immunity is called what? - ANSWER✔ innate immunity
(Note: non-specific response)
What are the general components of innate immunity? - ANSWER✔ 1. skin (physical/acidic
environment)
2. antimicrobial proteins (ex: lysozyme)
3. cilia (in lungs)
4. gastric juice (acidic environment)
5. symbiotic bacteria (digestive/vaginal)
All WBC's originate from stem cells located in what? - ANSWER✔ bone marrow
(Note: but some multiply and become non- naive in the lymph node)
What happens when a WBC recognizes a pathogen? - ANSWER✔ naive —> activated
What are the relative amounts of leukocytes in the blood to platelets and erythrocytes? - ANSWER✔
erythrocytes > platelets > leukocytes
What describes the second line of defense? - ANSWER✔ nonspecific and is also innate
, Which type of WBC's engulfs foreign particles, bacteria, dead or dying cells via phagocytosis? -
ANSWER✔ phagocytes
(Note: macrophages are
the largest phagocytes)
Which type of WBC's function in the destruction of pathogens in infected tissues - drawn to the infected
area by chemicals via chemotaxis? - ANSWER✔ neutrophils
(Note: a type
of phagocyte)
By what process do neutrophils enter tissues? - ANSWER✔ diapedesis
(Note: slip between
endothelial cells of
capillary)
Which type of WBC's circulate in blood until they move into tissues via diapedesis where they develop
into macrophages that phagocytize cell debris and pathogens, which are professional antigen-presenting
cells? - ANSWER✔ monocytes
(Note: a type of phagocyte)
Besides macrophages, what can monocytes also give rise to? - ANSWER✔ dendritic cells.
Which type of WBC's work collectively to surround and destroy multicellular parasites. These are not? -
ANSWER✔ eosinophils
(Note: NOT a type of phagocyte)
DETAILED ANSWERS|RATED AND GRADED A+ NEW UPDATE|
2026/2027
All blood cells arise from stem cell precursors located where? - ANSWER✔ bone marrow
The first line of defense in human immunity is called what? - ANSWER✔ innate immunity
(Note: non-specific response)
What are the general components of innate immunity? - ANSWER✔ 1. skin (physical/acidic
environment)
2. antimicrobial proteins (ex: lysozyme)
3. cilia (in lungs)
4. gastric juice (acidic environment)
5. symbiotic bacteria (digestive/vaginal)
All WBC's originate from stem cells located in what? - ANSWER✔ bone marrow
(Note: but some multiply and become non- naive in the lymph node)
What happens when a WBC recognizes a pathogen? - ANSWER✔ naive —> activated
What are the relative amounts of leukocytes in the blood to platelets and erythrocytes? - ANSWER✔
erythrocytes > platelets > leukocytes
What describes the second line of defense? - ANSWER✔ nonspecific and is also innate
, Which type of WBC's engulfs foreign particles, bacteria, dead or dying cells via phagocytosis? -
ANSWER✔ phagocytes
(Note: macrophages are
the largest phagocytes)
Which type of WBC's function in the destruction of pathogens in infected tissues - drawn to the infected
area by chemicals via chemotaxis? - ANSWER✔ neutrophils
(Note: a type
of phagocyte)
By what process do neutrophils enter tissues? - ANSWER✔ diapedesis
(Note: slip between
endothelial cells of
capillary)
Which type of WBC's circulate in blood until they move into tissues via diapedesis where they develop
into macrophages that phagocytize cell debris and pathogens, which are professional antigen-presenting
cells? - ANSWER✔ monocytes
(Note: a type of phagocyte)
Besides macrophages, what can monocytes also give rise to? - ANSWER✔ dendritic cells.
Which type of WBC's work collectively to surround and destroy multicellular parasites. These are not? -
ANSWER✔ eosinophils
(Note: NOT a type of phagocyte)
