Chapter 1
Immunology ⇒ physiological mechanisms that humans and other mammals use to defend
their bodies from invasion of other organisms→ when encountering the same disease will
become immune to the infection. Infectious disease caused by microorganisms, which
reproduce and evolve more rapidly than their human hosts → creates a vast population in
hosts. In response, human body will defend with immune system
Children born without an immune system often die in early childhood from common
infections. Highest risk at first infection for mortality. Infection on a large scale can lead to
pandemics → SARS-CoV-2.
Vaccination ⇒ procedure that prevents severe disease by exposing healthy individuals to
the infectious agents. Provides the immune system a way to become stronger against the
infection. Made from a fraction of the infectious disease.
1.1
Immune system is to protect the human body from infectious disease or other harmful
particles. Some microorganisms live in harmony with our bodies ⇒ commensal
microorganisms, all together known as the microbiota.
Commensal organisms enhance human nutrition by processing digested food and making
essential vitamins, also protecting against disease because their presence prevents
colonization by disease-causing organisms.
, 1.2
Microorganisms that cause disease are called pathogens, including microbes and other
microorganisms that are usually harmless but cause disease if humans immune system and
other defenses are weakened ⇒ opportunistic pathogens. Four kinds of pathogens:
● Viruses
● Bacteria
● Fungi
● Parasites → heterogenous group of unicellular protozoa and multicellular
invertebrates
Relationship between pathogens and human hosts can change which affects the disease
severity over time. Pathogenic organisms evolve adaptations that enable them to invade
their host, replicate and be propagated through human population. Rapid death of host not
useful for microbes → destroys the home and source of sustenance.Fatal pathogens often
evolve an accommodation with their host. Human populations evolve genetic resistance to
common disease, mostly being exposed to it in childhood.
1.3
Epithelium (cells that line the outer surface and inner cavities) is the formidable first defense
against infection, tough, impenetrable outer barrier of layers of keratinized cells. Skin can be
breached by physical damage, wounds, which exposes soft tissue and makes them
vulnerable to infection. Antiseptic procedures done from the 19th century to protect skin
during surgery.
Along the skin, other epithelial lines line the inner cavities: respiratory, gastrointestinal and
urogenital tracts. Here specialized tissues communicate with the environment and are
vulnerable to microbial invasion. Tissues are the mucosal surface (mucosae) which is
coated with mucus (thick fluid layer that contains glycoproteins, proteoglycans and enzymes
that protect epithelial cells from damage) that they secrete. In the respiratory system mucus
is removed through beating of cilia that characterize epithelium. Mucus here is replenished
by goblet cells (specialized in synthesis and secretion of mucus). Respiratory mucus is
constantly cleansed of unwanted material.
Epithelial surfaces secrete
antimicrobial substances. All
epithelia produce antimicrobial
peptides that kill bacteria, fungi and
enveloped viruses by perturbing their
membranes. Tears and saliva contain
lysozyme that kills bacteria by
degrading the cell walls. Also
important are the acidic environments
of the stomach, vagina and skin.
Immunology ⇒ physiological mechanisms that humans and other mammals use to defend
their bodies from invasion of other organisms→ when encountering the same disease will
become immune to the infection. Infectious disease caused by microorganisms, which
reproduce and evolve more rapidly than their human hosts → creates a vast population in
hosts. In response, human body will defend with immune system
Children born without an immune system often die in early childhood from common
infections. Highest risk at first infection for mortality. Infection on a large scale can lead to
pandemics → SARS-CoV-2.
Vaccination ⇒ procedure that prevents severe disease by exposing healthy individuals to
the infectious agents. Provides the immune system a way to become stronger against the
infection. Made from a fraction of the infectious disease.
1.1
Immune system is to protect the human body from infectious disease or other harmful
particles. Some microorganisms live in harmony with our bodies ⇒ commensal
microorganisms, all together known as the microbiota.
Commensal organisms enhance human nutrition by processing digested food and making
essential vitamins, also protecting against disease because their presence prevents
colonization by disease-causing organisms.
, 1.2
Microorganisms that cause disease are called pathogens, including microbes and other
microorganisms that are usually harmless but cause disease if humans immune system and
other defenses are weakened ⇒ opportunistic pathogens. Four kinds of pathogens:
● Viruses
● Bacteria
● Fungi
● Parasites → heterogenous group of unicellular protozoa and multicellular
invertebrates
Relationship between pathogens and human hosts can change which affects the disease
severity over time. Pathogenic organisms evolve adaptations that enable them to invade
their host, replicate and be propagated through human population. Rapid death of host not
useful for microbes → destroys the home and source of sustenance.Fatal pathogens often
evolve an accommodation with their host. Human populations evolve genetic resistance to
common disease, mostly being exposed to it in childhood.
1.3
Epithelium (cells that line the outer surface and inner cavities) is the formidable first defense
against infection, tough, impenetrable outer barrier of layers of keratinized cells. Skin can be
breached by physical damage, wounds, which exposes soft tissue and makes them
vulnerable to infection. Antiseptic procedures done from the 19th century to protect skin
during surgery.
Along the skin, other epithelial lines line the inner cavities: respiratory, gastrointestinal and
urogenital tracts. Here specialized tissues communicate with the environment and are
vulnerable to microbial invasion. Tissues are the mucosal surface (mucosae) which is
coated with mucus (thick fluid layer that contains glycoproteins, proteoglycans and enzymes
that protect epithelial cells from damage) that they secrete. In the respiratory system mucus
is removed through beating of cilia that characterize epithelium. Mucus here is replenished
by goblet cells (specialized in synthesis and secretion of mucus). Respiratory mucus is
constantly cleansed of unwanted material.
Epithelial surfaces secrete
antimicrobial substances. All
epithelia produce antimicrobial
peptides that kill bacteria, fungi and
enveloped viruses by perturbing their
membranes. Tears and saliva contain
lysozyme that kills bacteria by
degrading the cell walls. Also
important are the acidic environments
of the stomach, vagina and skin.
