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Flashcards in Cell Recognition Deck (22):

Why is a fetus rarely infected by a pathogen?

It is protected from the outside world by the mother and the placenta.


What is immunity?

When the body's defences are able to kill a pathogen before it can cause harm.


Does the body produce specific lymphocytes (white blood cells) in response to non self material?

No - there are 10 million different lymphocytes already in the body from birth.

Each one has the potential to bind to a specific antigen.

The lymphocyte with the complementary receptor (clonal selection) undergoes cell division to produce many of the desired lymphocyte.


What is an antigen?

A protein on the surface of a cell membrane.

That (in the case of a foreign antigen) will trigger an immune response.


Describe non-specific defences.

General action



Identify the 2 types of white blood cell.

  • cell mediated responses - T-lymphocytes (helpers (Th) or cytotoxic (Tc)
  • humoral responses - B-Lymphocytes


How is the immune response controlled in organ transplant patients to prevent organ rejection?

Immunosupressant drugs

Organs donated by family members - for a close tissue match.


Why is there a time lag between infection and an immune response?

  • clonal selection involves the lymphocyte with the complimentary protein to undergo cell division in order to destroy the pathogen - this takes time.
  • the correct lymphocyte binding to the non self antigen.


Antigens that belong to the body have _____ antigens on their cell membrane.



When can the immune system cause problems for medical patients?

People who have received organ transplants.

The transplanted organs have non self antigens.

The immune system will destroy the non self material.


Why is a fetus not attacked by its own lymphocytes when in the uterus?

Any lymphocytes that contain 'self receptors' are supressed or die.

The only remaining lymphocytes are those that respond to non-self material.


Foregn antigens are usually found on which 4 materials that can trigger an immune response?

  • Pathogens
  • Cells from other or the same species (organ transplants)
  • Toxins from pathogens
  • Cancer cells


Describe specific defences

Less rapid

Long lasting

Highly specific


Identify the non-specific defences against infection.

  • S.T.E.M.S (Skin, Tears, Earwax, Mucus, Stomach Acid)
  • Phagocytosis


Antigens can be which biological molecules?

Proteins (glycoproteins)

Lipids (glycolipids)


What is it about proteins that makes them useful as antigens?

Their specific 3D structure (tertiary structure) can form a variety of different 'labels' - easily recognised.


Sometimes lymphocytes develop in the bone marrow and have self receptors - initally only encounter self antigens. Why do they not destroy the person's cells?

  • They are programmed to die before they mature - apoptosis
  • remaining ones = non -self and only respond to foreign material.


Antigens that do not belong to the body have _____ antigens on their cell membrane.



What is a pathogen?

A microorganism that causes infectious disease.


Who is susceptible to pathogen infection?

Very old/young

People with compromised immune systems (AIDs)



What is meant by a SELF antigen?

A glycoprotein or glycolipid found on a cell surface membrane of a cell that belongs to the organism.


What is meant by a NON-SELF antigen?

A glycoprotein or glycolipid found on a cell surface membrane of a cell that does not belong to the organism.