White blood cells

[DoctorGeorge]

I understand that Lymphocytes produce antibodies which attach themselves to foreign bodies. How do the antibodies recognise the surface of the alien? Is it due to something chemical or physical?

thanks.

[Poison]

receptors...

[DoctorGeorge]

what are they? We've looked at white blood cells in school, but only in very sparse detail.

[Poison]

Receptors are the molecules on the lymphocytes. They are usually glycoproteins in structure. They help the cells to know about the envionment. When foreign bodies are present, lyphocytes recognise them by the help of its receptors.

[mith]

I think the foreign invaders get tagged by marker proteins.

[biostudent84]

It is a process called self/non-self recognition. All cells in your body made by your body have a protein marker. Whenever your lymphocytes detect any cell without this marker, an immune response is initiated, resulting in the destruction of these cells.

This is why blood tranfusions an organ transplants are so difficult. A donor needs to be found with identical protein markers. Blood is a little easier to match because only the ABO and the Rh proteins need to match. Organs are more difficult as there are 14 different types of protein markers that need to be identical.

[DoctorGeorge]

Awesome, thanks very much.

[Poison]

Can't protein markers also considered as receptors?

[D_Juggz]

i think what your getting at is - its actually when it comes down to it, something physical, the antibody recognises the antigen by its physical conformation ( i think ) - i stand open to correction.

[MrMistery]

Actually the phenomenon is of a much larger scale than it has been described. An antigen recognises one(AND ONLY ONE) protein at the level of the membrane. It can make a difference between 2 different proteins which resemble one another by their sequences, 2 different 3D conformations of the same protein, even 2 optical izomers.
How do they recognise them? Good question. Alberts book simply states that they are complementare proteins(like the SNARE complex, if you are in college you should know what that is). I always looked at it as a reversible chemical reaction, but i am not sure that is correct.
What you should know is that this is not restrictive of cells. It also works on viruses. The virus known as HIV1 has found a way to cheat this system. It keeps changing it's proteic layer so the antibodies don't recognise it
Hope this helps
Andrew