Biology: Immune System Questions and
Answers
immune system
The immune system utilizes a series of internal defense mechanisms that help protect the cells of the
body from pathogens.
pathogen
A pathogen is any agent, living or non-living, that can cause harm to the cells of the body (bacteria, virus,
harmful chemicals)
how do pathogens enter the body?
The pathogens can only cause harm if they enter our body. They can enter the body through the air we
breathe, the food we eat, through the wounds and cuts in our skin and so forth.
physical contact; soil, food, water, contaminated objects, bites and open wounds
antigen
a marker from a toxin or other foreign substance that induces an immune response in the body,
especially the production of antibodies.
Antigens serve as a target, and our body will mark the cells bearing the antigen as non-self
leukocytes
white blood cells are specialized cells that can defend our body from pathogens. All leukocytes originate
from cells in the bone marrow called hematopoietic stem cells. Leukocytes can in turn differentiate into
a variety of different cell types that each have their own unique function.
diapedesis
Leukocytes are amoeba-like cells that are capable of moving independently. They can move against the
flow of blood and can slip through the walls of capillaries and enter our tissue in a process
called diapedesis
the body has 3 lines of defense against infection:
1st line of defense - barriers to infection
2nd line of defense - nonspecific response or inflammatory response
3rd line of defense - immune response or specific immunity
the human immune system and its defense mechanisms can be divided into two types
non-specific (innate) immunity and specific (adaptive) immunity
, non-specific (innate) immunity
The innate immune system consists of non-specific defense mechanisms that act immediately following
infection. This is the primary line of defense against pathogens. Non-specific implies that it does not
depend on the presence of specific antigens; that is, the innate immune system attacks all pathogens
with equal likelihood
1st line of defense (innate immunity)
1st line of defense (innate immunity) = barriers to infection (block pathogen entry)
• skin layers forms a physical and chemical barrier against pathogens - our skin consists of several layers
that create a first line of defense against invading pathogens. The skin also
contains sebaceous glands that secrete fatty acids (antimicrobial properties) and this creates an
environment in which most bacteria cannot grow.
• mucous + cilia: goblet cells found along our air passageways produce a sticky and slimy layer of
mucous membrane that traps pathogens. Cilia in the respiratory tract removes pathogens to
the outside or to the stomach.
• acidity of stomach: parietel cells release HCl, which creates a highly acidic environment that kills off
most pathogens that enter the stomach via food or via mucous
• tears and saliva: lysozyme found in tears and saliva helps breakdown bacterial cell wall
• symbiotic bacteria: not all bacteria are bad! Symbiotic bacteria are our allies and out-compete their
more hostile relatives.
2nd line of defense (innate immunity)
2nd line of defense (innate immunity) = nonspecific response or inflammatory response
Inflammation:
Once the anatomical physical barriers are breached and the pathogen enters our tissue;
The innate immunity then initiates the process of inflammation. In this process, blood flow is increased
to the infected area. This blood brings several important white blood cells – neutrophils, eosinophils,
basophils, and macrophages, NK cells
relative number of leukocytes circulating in the blood from highest number of cells to lowest number of
cells in circulation:
Never Let Monkeys Eat Bananas
Neutrophils > Lymphocytes > Monocytes/Macrophages > Eosinophils > Basophils
chemotaxis
The process of moving to a location in response to a chemical signal is called chemotaxis. Chemo =
chemicals, and taxis = movement. In the inflammatory response, many white blood cells are drawn to
the site of injury via chemical signals to arrive.
Answers
immune system
The immune system utilizes a series of internal defense mechanisms that help protect the cells of the
body from pathogens.
pathogen
A pathogen is any agent, living or non-living, that can cause harm to the cells of the body (bacteria, virus,
harmful chemicals)
how do pathogens enter the body?
The pathogens can only cause harm if they enter our body. They can enter the body through the air we
breathe, the food we eat, through the wounds and cuts in our skin and so forth.
physical contact; soil, food, water, contaminated objects, bites and open wounds
antigen
a marker from a toxin or other foreign substance that induces an immune response in the body,
especially the production of antibodies.
Antigens serve as a target, and our body will mark the cells bearing the antigen as non-self
leukocytes
white blood cells are specialized cells that can defend our body from pathogens. All leukocytes originate
from cells in the bone marrow called hematopoietic stem cells. Leukocytes can in turn differentiate into
a variety of different cell types that each have their own unique function.
diapedesis
Leukocytes are amoeba-like cells that are capable of moving independently. They can move against the
flow of blood and can slip through the walls of capillaries and enter our tissue in a process
called diapedesis
the body has 3 lines of defense against infection:
1st line of defense - barriers to infection
2nd line of defense - nonspecific response or inflammatory response
3rd line of defense - immune response or specific immunity
the human immune system and its defense mechanisms can be divided into two types
non-specific (innate) immunity and specific (adaptive) immunity
, non-specific (innate) immunity
The innate immune system consists of non-specific defense mechanisms that act immediately following
infection. This is the primary line of defense against pathogens. Non-specific implies that it does not
depend on the presence of specific antigens; that is, the innate immune system attacks all pathogens
with equal likelihood
1st line of defense (innate immunity)
1st line of defense (innate immunity) = barriers to infection (block pathogen entry)
• skin layers forms a physical and chemical barrier against pathogens - our skin consists of several layers
that create a first line of defense against invading pathogens. The skin also
contains sebaceous glands that secrete fatty acids (antimicrobial properties) and this creates an
environment in which most bacteria cannot grow.
• mucous + cilia: goblet cells found along our air passageways produce a sticky and slimy layer of
mucous membrane that traps pathogens. Cilia in the respiratory tract removes pathogens to
the outside or to the stomach.
• acidity of stomach: parietel cells release HCl, which creates a highly acidic environment that kills off
most pathogens that enter the stomach via food or via mucous
• tears and saliva: lysozyme found in tears and saliva helps breakdown bacterial cell wall
• symbiotic bacteria: not all bacteria are bad! Symbiotic bacteria are our allies and out-compete their
more hostile relatives.
2nd line of defense (innate immunity)
2nd line of defense (innate immunity) = nonspecific response or inflammatory response
Inflammation:
Once the anatomical physical barriers are breached and the pathogen enters our tissue;
The innate immunity then initiates the process of inflammation. In this process, blood flow is increased
to the infected area. This blood brings several important white blood cells – neutrophils, eosinophils,
basophils, and macrophages, NK cells
relative number of leukocytes circulating in the blood from highest number of cells to lowest number of
cells in circulation:
Never Let Monkeys Eat Bananas
Neutrophils > Lymphocytes > Monocytes/Macrophages > Eosinophils > Basophils
chemotaxis
The process of moving to a location in response to a chemical signal is called chemotaxis. Chemo =
chemicals, and taxis = movement. In the inflammatory response, many white blood cells are drawn to
the site of injury via chemical signals to arrive.
