M
MICROBIOLOGY & PARASITOLOGY
C3
PREFINALS HOST RESPONSE TO INFECTION
HOST RESPONSE TO INFECTION - immunogenicity also depends on how the
Immunology antigen is administered.
- the study of the immune system and the - The dose of the antigen as well as the mode of
immune response. administration should be taken into
Immunogen consideration.
- any substance capable of inducing an immune - one might need a small amount of antigen to
response, whether humoral or cell-mediated or induce an immune response if the antigen
both. introduced is a protein as compared to a larger
Antigen amount if the antigen were a polysaccharide. In
- a substance recognized by the immune system, the same manner, antigens may not elicit a
whether by the B cell or the T cell, that serves reaction intramuscularly but may provoke
as the target of the immune response but may a good response when given
not necessarily lead to an immune response. subcutaneously.
Epitope
- the structure in the antigen that is recognized IMMUNE SYSTEM
by the B cell or the T cell. - system is composed of molecular and cellular
Hapten components that are derived from the central
- a substance that is of low molecular weight that (primary) and peripheral (secondary) lymphoid
can only induce an immune response if bound to organs.
another substance that is already immunogenic Central Lymphoid Organs
(carrier molecule). - are the primary sites for differentiation and
maturation of the important cells that play an
PROPERTIES OF ANTIGENS important role in adaptive immunity which are
properties that an antigen must possess to the T lymphocytes (or T cells) and the B
make it immunogenic: lymphocytes (or B cells).
foreignness and genetic composition, - These consist of the bone marrow and the
chemical composition and complexity, thymus.
molecular size and stability, - The bone marrow is the site from where blood
mode of entry of the antigen. cells originate.
Foreignnes and genetic composition - The precursor cells for lymphocytes found in
- Antigens are genetically foreign to the host or the adult bone marrow and this is where they
recognized by the body as non-self. differentiate into B cells and T cells.
- most humans are exposed to similar - Once differentiated, B cells remain in the bone
environmental components (e.g., dust) but not marrow and undergo maturation in the bone
all will have similar reactions. One person may marrow.
manifest a hypersensitivity reaction to a - the T cells will go out of the bone marrow as
substance that will provoke no reaction in immature and incompetent forms then go to the
another. This is because each individual has thymus where they mature and become
a different genetic composition from competent.
another. - After maturation, the mature B cells and T
cells proceed to the peripheral lymphoid
chemical composition and complexity organs to await any antigen that may
- chemical composition and complexity of an enter the body.
antigen may also affect its immunogenicity. Peripheral Lymphoid Organs
- Most organic substances can be antigenic - consist of the lymph nodes, spleen, and the
except for pure lipids and nucleic acids. Of the mucosa- associated lymphoid tissues (MALT),
different chemical groupings, proteins are the o tonsils, adenoids,
most immunogenic. This is because proteins o Peyer's patches in the ileum,
are larger molecules than others that have o appendix.
more complex structures. Likewise, between These organs are the site of
a pure protein and a glycoprotein, a reactivity of lymphoid cells.
glycoprotein will be more antigenic because its These are where antigens are
structure is more complex. trapped and subsequently
encounter the T and B cells.
molecular size and stability - Antigens are brought to these peripheral
- is another property that can affect its lymphoid organs where the cells needed for
immunogenicity. their destruction are located.
- As a rule, molecules with molecular weights - Both mature T cells and B cells are found
below 10,000 daltons are weakly immunogenic in the peripheral lymphoid organs.
or not immunogenic at all.
- Those with molecular weights greater than
10,000 daltons are very potent immunogens.
- There are some substances that have high
molecular weights that break up into smaller
molecules once they enter the body, in which
case they lose their immunogenicity.
mode of entry of the antigen
Hannah Adan 1
, M
MICROBIOLOGY & PARASITOLOGY
C3
PREFINALS HOST RESPONSE TO INFECTION
- The granules of both eosinophils and basophils
contain histamine which when released is
responsible for the changes seen during the
initial phase of an allergic reaction.
Platelets
CELLS OF IMMUNE SYSTEM - are membrane-bound cell fragments that are
- various responses of the human immune system derived from large cells called
are mediated by specific cells and the megakaryocytes.
substances they produce. - Platelets are mainly involved in blood
- These cells include the white blood cells coagulation, however, they secrete substances
which include: that play a role in inflammation.
o granulocytes (e.g., neutrophil) 50%-80%
of white blood cells
o lymphocytes, approximately 20%-45%
of total white blood cells
o monocytes and macrophages,
Neutrophils
- play a major role in acute inflammation as well
as in bacterial infections.
Lymphocytes
- involved in chronic inflammation
- are the predominant inflammatory cells in viral
infections.
Macrophages
- also involved in chronic Inflammation
Antigen Presenting Cells
- are cells that are involved in the processing and Natural Killer Cells (NK/Null cells)
presentation of antigens to the T cells. - are large granular lymphocytes.
- These include - They were originally classified as cytotoxic T
o Macrophages cells because they had the same manner of
o B cells, killing target antigens.
o dendritic cells - studies conducted on their structures showed
o Langerhans cells in the skin that all T cells had a T-Cell Receptor (TCR)
o Kupffer cells in the liver on their surface that was not present in NK
o glial cells in the central system. cells, hence NK cells are not classified
anymore as T cells.
- B cells, macrophages, and dendritic cells
- NK cells are classified as large granular
are the professional antigen presenting cells,
lymphocytes and are part of the body's innate
the most important of which are the dendritic
immune system.
cells.
o Some of these cells are found in
association with lymphoid follicles in the
lymph nodes and are thus called
follicular dendritic cells.
- Langerhans cells in the skin also bring
antigens to the paracortical zone of the lymph
node where they are called interdigitating
dendritic cells.
- Dendritic cells are considered as the true link
between innate and adaptive immunity.
WBC in Innate arm of IS
Eosinophils
Basophils
Platelets
Eosinophils
- possess eosinophilic granules that play a role in
type I hypersensitivity reaction or allergy
- secrete a substance that is called major basic
protein that is toxic to parasites, especially
helminths or worms.
Basophils
- play a role in allergies
Hannah Adan 2
MICROBIOLOGY & PARASITOLOGY
C3
PREFINALS HOST RESPONSE TO INFECTION
HOST RESPONSE TO INFECTION - immunogenicity also depends on how the
Immunology antigen is administered.
- the study of the immune system and the - The dose of the antigen as well as the mode of
immune response. administration should be taken into
Immunogen consideration.
- any substance capable of inducing an immune - one might need a small amount of antigen to
response, whether humoral or cell-mediated or induce an immune response if the antigen
both. introduced is a protein as compared to a larger
Antigen amount if the antigen were a polysaccharide. In
- a substance recognized by the immune system, the same manner, antigens may not elicit a
whether by the B cell or the T cell, that serves reaction intramuscularly but may provoke
as the target of the immune response but may a good response when given
not necessarily lead to an immune response. subcutaneously.
Epitope
- the structure in the antigen that is recognized IMMUNE SYSTEM
by the B cell or the T cell. - system is composed of molecular and cellular
Hapten components that are derived from the central
- a substance that is of low molecular weight that (primary) and peripheral (secondary) lymphoid
can only induce an immune response if bound to organs.
another substance that is already immunogenic Central Lymphoid Organs
(carrier molecule). - are the primary sites for differentiation and
maturation of the important cells that play an
PROPERTIES OF ANTIGENS important role in adaptive immunity which are
properties that an antigen must possess to the T lymphocytes (or T cells) and the B
make it immunogenic: lymphocytes (or B cells).
foreignness and genetic composition, - These consist of the bone marrow and the
chemical composition and complexity, thymus.
molecular size and stability, - The bone marrow is the site from where blood
mode of entry of the antigen. cells originate.
Foreignnes and genetic composition - The precursor cells for lymphocytes found in
- Antigens are genetically foreign to the host or the adult bone marrow and this is where they
recognized by the body as non-self. differentiate into B cells and T cells.
- most humans are exposed to similar - Once differentiated, B cells remain in the bone
environmental components (e.g., dust) but not marrow and undergo maturation in the bone
all will have similar reactions. One person may marrow.
manifest a hypersensitivity reaction to a - the T cells will go out of the bone marrow as
substance that will provoke no reaction in immature and incompetent forms then go to the
another. This is because each individual has thymus where they mature and become
a different genetic composition from competent.
another. - After maturation, the mature B cells and T
cells proceed to the peripheral lymphoid
chemical composition and complexity organs to await any antigen that may
- chemical composition and complexity of an enter the body.
antigen may also affect its immunogenicity. Peripheral Lymphoid Organs
- Most organic substances can be antigenic - consist of the lymph nodes, spleen, and the
except for pure lipids and nucleic acids. Of the mucosa- associated lymphoid tissues (MALT),
different chemical groupings, proteins are the o tonsils, adenoids,
most immunogenic. This is because proteins o Peyer's patches in the ileum,
are larger molecules than others that have o appendix.
more complex structures. Likewise, between These organs are the site of
a pure protein and a glycoprotein, a reactivity of lymphoid cells.
glycoprotein will be more antigenic because its These are where antigens are
structure is more complex. trapped and subsequently
encounter the T and B cells.
molecular size and stability - Antigens are brought to these peripheral
- is another property that can affect its lymphoid organs where the cells needed for
immunogenicity. their destruction are located.
- As a rule, molecules with molecular weights - Both mature T cells and B cells are found
below 10,000 daltons are weakly immunogenic in the peripheral lymphoid organs.
or not immunogenic at all.
- Those with molecular weights greater than
10,000 daltons are very potent immunogens.
- There are some substances that have high
molecular weights that break up into smaller
molecules once they enter the body, in which
case they lose their immunogenicity.
mode of entry of the antigen
Hannah Adan 1
, M
MICROBIOLOGY & PARASITOLOGY
C3
PREFINALS HOST RESPONSE TO INFECTION
- The granules of both eosinophils and basophils
contain histamine which when released is
responsible for the changes seen during the
initial phase of an allergic reaction.
Platelets
CELLS OF IMMUNE SYSTEM - are membrane-bound cell fragments that are
- various responses of the human immune system derived from large cells called
are mediated by specific cells and the megakaryocytes.
substances they produce. - Platelets are mainly involved in blood
- These cells include the white blood cells coagulation, however, they secrete substances
which include: that play a role in inflammation.
o granulocytes (e.g., neutrophil) 50%-80%
of white blood cells
o lymphocytes, approximately 20%-45%
of total white blood cells
o monocytes and macrophages,
Neutrophils
- play a major role in acute inflammation as well
as in bacterial infections.
Lymphocytes
- involved in chronic inflammation
- are the predominant inflammatory cells in viral
infections.
Macrophages
- also involved in chronic Inflammation
Antigen Presenting Cells
- are cells that are involved in the processing and Natural Killer Cells (NK/Null cells)
presentation of antigens to the T cells. - are large granular lymphocytes.
- These include - They were originally classified as cytotoxic T
o Macrophages cells because they had the same manner of
o B cells, killing target antigens.
o dendritic cells - studies conducted on their structures showed
o Langerhans cells in the skin that all T cells had a T-Cell Receptor (TCR)
o Kupffer cells in the liver on their surface that was not present in NK
o glial cells in the central system. cells, hence NK cells are not classified
anymore as T cells.
- B cells, macrophages, and dendritic cells
- NK cells are classified as large granular
are the professional antigen presenting cells,
lymphocytes and are part of the body's innate
the most important of which are the dendritic
immune system.
cells.
o Some of these cells are found in
association with lymphoid follicles in the
lymph nodes and are thus called
follicular dendritic cells.
- Langerhans cells in the skin also bring
antigens to the paracortical zone of the lymph
node where they are called interdigitating
dendritic cells.
- Dendritic cells are considered as the true link
between innate and adaptive immunity.
WBC in Innate arm of IS
Eosinophils
Basophils
Platelets
Eosinophils
- possess eosinophilic granules that play a role in
type I hypersensitivity reaction or allergy
- secrete a substance that is called major basic
protein that is toxic to parasites, especially
helminths or worms.
Basophils
- play a role in allergies
Hannah Adan 2
