1
Immunology
Lecture 1:
Immunology: scientific discipline that studies the immune
system, which serves to protect your body from infectious
agents and cancer
Infectious diseases
- Extracellular bacteria
- Intracellular bacteria
- Viruses
- Fungi
- Parasites
Vaccination (since 1798, Jenner) → understanding that specific germs cause specific diseases.
Koch’s postulate: critical step forward in identifying causal agents
Koch’s postulate
1) Germ is found in diseased but not healthy organisms
2) The germ can be isolated from the diseased organism
3) The germ causes diseases when transferred
4) The germ can be isolated again
Infectious diseases
● Polio: highly contagious virus; paralysis and deformation in 1/200 patients
● Measles: highly contagious virus, with very severe complication and often resulting in
death
● Diphtheria: arterial infection, most common cause of pediatric death before a vaccine
became available. After Diagnosis: 10% of patients die with and 50% die without
treatment
Studying and understanding the interactions between infectious agents and the immune system
has led to eradication of the viral disease smallpox and strong reductions in the incidence of a
large series of other infectious disease
→ with loss of confidence in vaccines, infectious diseases are resurfacing
→ not bad in isolated islands, but when disease gets an outbreak there, it will be (example:
Samoa measles, death rate was 1.5% of all infection children on the island)
SARS-CoV-2
2020 slide: 62.5 million cases; 1.5 million death confirmed → no vaccine or treatment
2021 slide: 265 million causes; 5.2 million deaths confirmed → vaccine and better treatment
2022 slide: 645 million ases; 6.6 million death confirmed
1
, 2
Vaccines are effective
- First 4 graphs: Total numbers of hospitalized
COVID-19 patients per day in 4 age groups
- In younger age groups more unvaccinated
patients, in elderly: more vaccinated
- Second 4 graphs: Proportion of hospitalized
COVID-19 patients per day in 4 age groups per
100.000 people
- In all age groups far more unvaccinated
patients are hospitalised per 100.00
- Third 4 graphs: total number of COVID-19
patients in the ICU per day in 4 age groups
- In younger age groups, more unvaccinated
patients end up in ICU (severe COVID), in
elderly: equal numbers
→ This translates to 20 out of 30 COVID-19 patients in
the ICU are not vaccinated
→ A little less than 5 out of 30 people in the
Netherlands were not vaccinated
→ This “real-live” experiment clearly shows that
vaccination protects against severe COVID-19 after
SARS-CoV-2 infection
We knew this prior to COVID
- Meningococcal disease: caused by a bacteria
that can inhibit the mouth and throat. In rare
occasions, the bacteria can enter the circulation, leading to sepsis and meningitis, with a
death rate around 10% and severe complications (including neurological symptoms,
deformations, and amputation)
2
, 3
- In 2002, vaccinations against type C has nearly eradicated this meningococcus type
- Meningococcal type W has seen a strong increase since 2017
- This meningococcal type is very aggressive, leading to a new vaccination program for
this disease (2018)
Do vaccines actually help?
→ Second vaccination program; incidence dropped in 2019 except for 80+ group
→ Also for the C-strain, the vaccination program eradicated the outbreak of meningococcal
disease
More vaccines are needed
- Respiratory Syncytial virus (RSV), a cause of common cold with yearly seasonal
epidemics around the globe
- In preterm infants, RSV can cause severe complications. In susceptible children, also
those carried to term, RSV infections in the first year can contribute to asthma inception
- Due to relief of COVID-19 lockdown restrictions, the Netherlands had an RSV pandemic
with pediatric ICUs overflowing in summer 2021
Cells of the immune system
● White blood cells, or leucocytes, are the most important cells in the immune system.
However, other cells also play an important role, including epithelial and endothelial cells
● Leukocytes originate from the hematopoietic stem cell
● Mature leukocytes often circulate the body using the blood and lymph systems, However
tissue also harbor a large number of specialised tissue-resident leukocytes
3
, 4
Innate vs Adaptive
Innate Acquired / adaptive
Specificity: groups of microorganisms Specificity: a single (protein) antigen
Fast response, first defense Slow response, very powerful
Always active Induced by specific trigger
Encoded in the germline DNA Requires DNA rearrangement
Memory response by epigenetic Source of specific immunological memory
programming only and basis for vaccination
The different steps in the immune response start at different moments after injection, and are
then active for different time periods as well
Immunological memory of the adaptive immune system can offer lifelong protection
4
Immunology
Lecture 1:
Immunology: scientific discipline that studies the immune
system, which serves to protect your body from infectious
agents and cancer
Infectious diseases
- Extracellular bacteria
- Intracellular bacteria
- Viruses
- Fungi
- Parasites
Vaccination (since 1798, Jenner) → understanding that specific germs cause specific diseases.
Koch’s postulate: critical step forward in identifying causal agents
Koch’s postulate
1) Germ is found in diseased but not healthy organisms
2) The germ can be isolated from the diseased organism
3) The germ causes diseases when transferred
4) The germ can be isolated again
Infectious diseases
● Polio: highly contagious virus; paralysis and deformation in 1/200 patients
● Measles: highly contagious virus, with very severe complication and often resulting in
death
● Diphtheria: arterial infection, most common cause of pediatric death before a vaccine
became available. After Diagnosis: 10% of patients die with and 50% die without
treatment
Studying and understanding the interactions between infectious agents and the immune system
has led to eradication of the viral disease smallpox and strong reductions in the incidence of a
large series of other infectious disease
→ with loss of confidence in vaccines, infectious diseases are resurfacing
→ not bad in isolated islands, but when disease gets an outbreak there, it will be (example:
Samoa measles, death rate was 1.5% of all infection children on the island)
SARS-CoV-2
2020 slide: 62.5 million cases; 1.5 million death confirmed → no vaccine or treatment
2021 slide: 265 million causes; 5.2 million deaths confirmed → vaccine and better treatment
2022 slide: 645 million ases; 6.6 million death confirmed
1
, 2
Vaccines are effective
- First 4 graphs: Total numbers of hospitalized
COVID-19 patients per day in 4 age groups
- In younger age groups more unvaccinated
patients, in elderly: more vaccinated
- Second 4 graphs: Proportion of hospitalized
COVID-19 patients per day in 4 age groups per
100.000 people
- In all age groups far more unvaccinated
patients are hospitalised per 100.00
- Third 4 graphs: total number of COVID-19
patients in the ICU per day in 4 age groups
- In younger age groups, more unvaccinated
patients end up in ICU (severe COVID), in
elderly: equal numbers
→ This translates to 20 out of 30 COVID-19 patients in
the ICU are not vaccinated
→ A little less than 5 out of 30 people in the
Netherlands were not vaccinated
→ This “real-live” experiment clearly shows that
vaccination protects against severe COVID-19 after
SARS-CoV-2 infection
We knew this prior to COVID
- Meningococcal disease: caused by a bacteria
that can inhibit the mouth and throat. In rare
occasions, the bacteria can enter the circulation, leading to sepsis and meningitis, with a
death rate around 10% and severe complications (including neurological symptoms,
deformations, and amputation)
2
, 3
- In 2002, vaccinations against type C has nearly eradicated this meningococcus type
- Meningococcal type W has seen a strong increase since 2017
- This meningococcal type is very aggressive, leading to a new vaccination program for
this disease (2018)
Do vaccines actually help?
→ Second vaccination program; incidence dropped in 2019 except for 80+ group
→ Also for the C-strain, the vaccination program eradicated the outbreak of meningococcal
disease
More vaccines are needed
- Respiratory Syncytial virus (RSV), a cause of common cold with yearly seasonal
epidemics around the globe
- In preterm infants, RSV can cause severe complications. In susceptible children, also
those carried to term, RSV infections in the first year can contribute to asthma inception
- Due to relief of COVID-19 lockdown restrictions, the Netherlands had an RSV pandemic
with pediatric ICUs overflowing in summer 2021
Cells of the immune system
● White blood cells, or leucocytes, are the most important cells in the immune system.
However, other cells also play an important role, including epithelial and endothelial cells
● Leukocytes originate from the hematopoietic stem cell
● Mature leukocytes often circulate the body using the blood and lymph systems, However
tissue also harbor a large number of specialised tissue-resident leukocytes
3
, 4
Innate vs Adaptive
Innate Acquired / adaptive
Specificity: groups of microorganisms Specificity: a single (protein) antigen
Fast response, first defense Slow response, very powerful
Always active Induced by specific trigger
Encoded in the germline DNA Requires DNA rearrangement
Memory response by epigenetic Source of specific immunological memory
programming only and basis for vaccination
The different steps in the immune response start at different moments after injection, and are
then active for different time periods as well
Immunological memory of the adaptive immune system can offer lifelong protection
4
