more disease and immune system

• Lupus


  • A notoriously hard disease to diagnose as the symptoms that individual present with often vary drastically
  • The most distinctive symptom is a butterfly rash across the face
  • Women tend to suffer from the disease more than men
  • The connective tissue of the body is attacked by the immune system, affecting several organs
  • Areas affected include the joints, kidneys, heart, lungs and skin
  • It causes long-term destruction
• Rheumatoid arthritis


  • An autoimmune disease that solely affects the joints
  • It is different from osteoarthritis in several ways
  • It usually begins in the fingers and hands, spreading to the shoulders and elsewhere
  • Symptoms include muscle spasms, inflamed tendons, lethargy and constant joint pain
• Causes of autoimmune diseases

  • Genetics is an influencing factor
  • Susceptibility to an autoimmune disease was shown to be inherited
  • Susceptibility is the likelihood of an individual developing the disease when exposed to the specific pathogen or stimulus
  • The environment is also important
  • When individuals moved from areas of low autoimmune disease prevalence (like Japan) to areas of higher autoimmune disease prevalence (like the USA) they showed an increased chance of developing an autoimmune disease
• Vaccine


  • A suspension of antigens that are intentionally put into the body to induce artificial active immunity
  • A specific immune response where antibodies are released by plasma cells
• Types of vaccines


  • Live attenuated
  • Inactivated
• How vaccines cause long-term immunity

  • Vaccinations produce long-term immunity as they cause memory cells to be created
  • The immune system remembers the antigen when reencountered and produces antibodies to it, in what is a faster, stronger secondary response
• Problems with vaccination


  • People having a poor response
  • Antigenic variation
  • Antigenic drift
  • Antigenic shift
  • Antigenic concealment
  • Cross breeding
• Antigenic variation


  The variation (due to major changes) in the antigens of pathogens causes the vaccines to not trigger an immune response or diseases caused by eukaryotes (eg. malaria) have too many antigens on their cell surface membranes making it difficult to produce vaccines that would prompt the immune system quickly enough
• Antigenic drift


  Over time there are small changes in the structure and shape of antigens (within the same strain of virus)
• Antigenic shift


  There are major changes in antigens (within the same strain of virus)
• Antigenic concealment


  • The pathogen 'hides' from the immune system by:
  • Living inside cells
  • Coating their bodies in host proteins
  • Parasitising immune cells such as macrophages and T cells (eg. HIV)
  • Remaining in parts of the body that are difficult for vaccines to reach (eg. Vibrio cholerae - cholera, remains in the small intestine)
• Cross-breeding


  • When different strains of the virus invade the same cell, producing new viruses with antigens from different strains (essentially the strains swap antigens with each other)
  • The strains of influenza viruses that cause human influenza have been known to crossbreed with viruses that cause similar diseases in other animals
  • This crossbreeding can produce new strains of the human influenza virus that cause pandemics (as no individuals have immunity against them)
  • Every year the World Health Organisation (WHO) tries to provide information about strains that are likely to spread in order to aid government decisions and the development of flu vaccines
• Herd immunity


  • Arises when a sufficiently large proportion of the population has been vaccinated (and are therefore immune) which makes it difficult for a pathogen to spread within that population
  • Those who are not immunised are protected and unlikely to contract it as the levels of the disease are so low
  • It is very important as it allows for the individuals who are unable to be vaccinated (e.g. children and those with weak immune systems) to be protected from the disease
• Ring immunity


  • It is another way by which mass vaccination programmes can work
  • People living or working near a vulnerable (or infected) person are vaccinated in order to prevent them from catching and transmitting the disease
  • The vaccinated individuals do not spread the pathogen onto others so those vulnerable individuals "within the ring" are protected as the people they interact with will not have the disease
• Challenges of eradicating disease

  • Some pathogens are simply complicated and present with disease processes that are not straightforward and so a successful vaccine has not been developed
  • Diseases that could be eradicated where a vaccine does exist, have not been eliminated because too few in the community have been vaccinated
  • Unstable political situations
  • Lack of public health facilities
• Live attenuated vaccines


  • They contain whole pathogens (e.g. bacteria and viruses) that have been 'weakened'
  • These weakened pathogens multiply slowly allowing for the body to recognise the antigens and trigger the primary immune response (plasma cells to produce antibodies)
  • These vaccines tend to produce a stronger and longer-lasting immune response
  • An example is the MMR vaccine
• Inactivated vaccines


  • They contain whole pathogens that have been killed ('whole killed') or small parts ('subunit') of the pathogens (eg. proteins or sugars or harmless forms of the toxins - toxoids)
  • As inactivated vaccines do not contain living pathogens they cannot cause disease, even for those with weak immune systems
  • However, these vaccines do not trigger a strong or long-lasting immune response like live attenuated vaccines. Repeated doses and/or booster doses are often required
  • An example is the polio vaccine
• Ways in which new drugs are discovered and developed

  • Finding candidate genes
  • Identifying molecules that fit into drug targets
  • Modifying drugs
  • Identification of useful compounds produced by organisms
• Synthetic biology


  A recent area of research that aims to create new biological parts, devices, and systems, or to redesign systems that already exist in nature
• Antibiotics


  • Chemical substances that inhibit or kill bacterial cells with little or no harm to human tissue
  • Many antibiotics are derived from naturally occurring substances that are harmful to prokaryotic cells (structurally or physiologically) but usually do not affect eukaryotic cells
  • The aim of antibiotic use is to aid the body's immune system with fighting a bacterial infection
• Sir Alexander Fleming discovered penicillin
• Bactericidal antibiotics


  Antibiotics that kill bacteria
• Bacteriostatic antibiotics


  Antibiotics that do not actually kill bacteria but rather inhibit their growth
• What happens when an antibiotic is present with bacteria (resistance and non-resistance)

  • Bacteria with the allele for antibiotic resistance have a massive selective advantage so they are more likely to survive, reproduce and pass genome (including resistance alleles)
  • Those without alleles are less likely to die and reproduce
  • Over several generations, the entire population of bacteria may be antibiotic-resistant
• Consequences of antibiotic resistance

  • Commonly prescribed antibiotics are becoming less effective
  • The main reason is Overuse of antibiotics and antibiotics being prescribed when not necessary
  • Large scale use of antibiotics in farming to prevent disease when livestock are kept in close quarters, even when animals are not sick
  • Patients failing to complete the full course of antibiotics prescribed by doctors
  • These factors have led to a reduction in the effectiveness of antibiotics, and an increase in the incidence of antibiotic resistance
  • In addition, resistance may first appear in a non-pathogenic bacterium, but then be passed on to a pathogenic species by horizontal transmission
  • There is a constant race to find new antibiotics as resistant strains are continuously evolving
• Staphylococcus aureus


  • The most common example of a resistant bacteria is a strain of Staphylococcus aureus that has developed resistance to a powerful antibiotic, methicillin and is now known as MRSA (Methicillin-resistant Staphylococcus aureus)
  • Some MRSA strains have also become resistant to other antibiotics (eg. penicillin)
  • S.aureus usually lives on human skin, without causing disease however when there is an opportunity for the pathogen to enter the body (e.g. surgical wound) they can cause serious disease
• How to reduce antibiotic resistance and its impact

  • Tighter controls in countries in antibiotic prescription
  • Doctors avoiding the overuse of antibiotics when not needed
  • Finish the entire course
  • Not being used for viral infections
  • Using highly specific antibiotics
  • Less use of antibiotics in agriculture
• How to limit the spread of already-resistant strains

  • Ensuring good hygiene practices such as handwashing and the use of hand sanitisers (this has reduced the rates of resistant strains of bacteria, such as MRSA, in hospitals)
  • Isolating infected patients to prevent the spread of resistant strains, in particular in surgical wards where MRSA can infect surgical wounds