what do antigens look like?

[Amalan]

Im curious in seeing one under a microscope. google images just has artist interpretations and wikipedia portrays them like lego building blocks. kinda curious to seeing various forms of antigens if anyone knows where to get some good pics?

[Ryan_m_b]

Welcome to PF Amalan, antigens are any molecule/chemical that triggers the production of antibodies in the immune system. As such antigens are hugely diverse, most would be impossible to see under a microscope because they are so small that they are invisible to visible light.

Here's some examples for you
Melittin (http://www.google.com/imgres?imgurl=http://gold.cchem.berkeley.edu/~macfady/melittin.jpg&imgrefurl=http://gold.cchem.berkeley.edu/~macfady/&usg=__jkV6bv1spJXLJTqQ00gWXTv1Zb0=&h=435&w=471&sz=497&hl=en&start=0&zoom=1&tbnid=jPOQZQcdl2ON6M:&tbnh=156&tbnw=169&ei=fIjaTfTGEoKBswaNqaHuAg&prev=/search%3Fq%3Dmelittin%26um%3D1%26hl%3Den%26sa%3DN% 26biw%3D1366%26bih%3D667%26tbm%3Disch&um=1&itbs=1&iact=hc&vpx=322&vpy=121&dur=1058&hovh=216&hovw=234&tx=148&ty=68&sqi=2&page=1&ndsp=18&ved=1t:429,r:1,s:0) the principle component of a Bee sting (this is an antigen if you are allergic)
P24 (http://www.google.com/imgres?imgurl=http://1.bp.blogspot.com/_-3vLd7sA4vY/THsFusddeSI/AAAAAAAAAAM/9QhXQdzVMIU/s1600/gag%2Bp24.gif&imgrefurl=http://aptamerstream.blogspot.com/2010/08/aptamer-selection-for-integral-hiv.html&usg=__Nqt2qivz1EhcpoJJsPb95HXk2v0=&h=200&w=165&sz=16&hl=en&start=0&zoom=1&tbnid=rKJjT12KFFGHNM:&tbnh=160&tbnw=132&ei=uInaTYDMBofNtAa7hZD4Ag&prev=/search%3Fq%3Dp24%2Bcapsid%2Bprotein%26um%3D1%26hl% 3Den%26biw%3D1366%26bih%3D667%26tbm%3Disch&um=1&itbs=1&iact=hc&vpx=1162&vpy=126&dur=155&hovh=160&hovw=132&tx=74&ty=77&sqi=2&page=1&ndsp=19&ved=1t:429,r:5,s:0) a HIV antigen
Some Rhesus (http://www.google.com/imgres?imgurl=http://sinoemedicalassociation.org/obgyn/gynusmle/Rh%2520isoimmunization_files/image007.jpg&imgrefurl=http://sinoemedicalassociation.org/obgyn/gynusmle/Rh%2520isoimmunization.htm&usg=__LALBDJ9Bnn-qKWU8mAM2M5IbH2c=&h=450&w=600&sz=42&hl=en&start=33&zoom=1&tbnid=_KKcS6OBm2dZDM:&tbnh=156&tbnw=242&ei=LIraTbm9IsGr8AOxmLCEBQ&prev=/search%3Fq%3Drhesus%2Bantigen%26um%3D1%26hl%3Den%2 6sa%3DN%26biw%3D1366%26bih%3D667%26tbm%3Disch0%2C1 280&um=1&itbs=1&iact=hc&vpx=1066&vpy=255&dur=692&hovh=194&hovw=259&tx=133&ty=115&sqi=2&page=3&ndsp=16&ved=1t:429,r:15,s:33&biw=1366&bih=667) antigens.

Something that you should probably know is that there are many ways of schematically representing molecules known as molecular models (http://en.wikipedia.org/wiki/Molecular_model)

[Amalan]

Welcome to PF Amalan, antigens are any molecule/chemical that triggers the production of antibodies in the immune system. As such antigens are hugely diverse, most would be impossible to see under a microscope because they are so small that they are invisible to visible light.

Here's some examples for you
Melittin (http://www.google.com/imgres?imgurl=http://gold.cchem.berkeley.edu/~macfady/melittin.jpg&imgrefurl=http://gold.cchem.berkeley.edu/~macfady/&usg=__jkV6bv1spJXLJTqQ00gWXTv1Zb0=&h=435&w=471&sz=497&hl=en&start=0&zoom=1&tbnid=jPOQZQcdl2ON6M:&tbnh=156&tbnw=169&ei=fIjaTfTGEoKBswaNqaHuAg&prev=/search%3Fq%3Dmelittin%26um%3D1%26hl%3Den%26sa%3DN% 26biw%3D1366%26bih%3D667%26tbm%3Disch&um=1&itbs=1&iact=hc&vpx=322&vpy=121&dur=1058&hovh=216&hovw=234&tx=148&ty=68&sqi=2&page=1&ndsp=18&ved=1t:429,r:1,s:0) the principle component of a Bee sting (this is an antigen if you are allergic)
P24 (http://www.google.com/imgres?imgurl=http://1.bp.blogspot.com/_-3vLd7sA4vY/THsFusddeSI/AAAAAAAAAAM/9QhXQdzVMIU/s1600/gag%2Bp24.gif&imgrefurl=http://aptamerstream.blogspot.com/2010/08/aptamer-selection-for-integral-hiv.html&usg=__Nqt2qivz1EhcpoJJsPb95HXk2v0=&h=200&w=165&sz=16&hl=en&start=0&zoom=1&tbnid=rKJjT12KFFGHNM:&tbnh=160&tbnw=132&ei=uInaTYDMBofNtAa7hZD4Ag&prev=/search%3Fq%3Dp24%2Bcapsid%2Bprotein%26um%3D1%26hl% 3Den%26biw%3D1366%26bih%3D667%26tbm%3Disch&um=1&itbs=1&iact=hc&vpx=1162&vpy=126&dur=155&hovh=160&hovw=132&tx=74&ty=77&sqi=2&page=1&ndsp=19&ved=1t:429,r:5,s:0) a HIV antigen
Some Rhesus (http://www.google.com/imgres?imgurl=http://sinoemedicalassociation.org/obgyn/gynusmle/Rh%2520isoimmunization_files/image007.jpg&imgrefurl=http://sinoemedicalassociation.org/obgyn/gynusmle/Rh%2520isoimmunization.htm&usg=__LALBDJ9Bnn-qKWU8mAM2M5IbH2c=&h=450&w=600&sz=42&hl=en&start=33&zoom=1&tbnid=_KKcS6OBm2dZDM:&tbnh=156&tbnw=242&ei=LIraTbm9IsGr8AOxmLCEBQ&prev=/search%3Fq%3Drhesus%2Bantigen%26um%3D1%26hl%3Den%2 6sa%3DN%26biw%3D1366%26bih%3D667%26tbm%3Disch0%2C1 280&um=1&itbs=1&iact=hc&vpx=1066&vpy=255&dur=692&hovh=194&hovw=259&tx=133&ty=115&sqi=2&page=3&ndsp=16&ved=1t:429,r:15,s:33&biw=1366&bih=667) antigens.

Something that you should probably know is that there are many ways of schematically representing molecules known as molecular models (http://en.wikipedia.org/wiki/Molecular_model)

if they are impossible to see, how do we know its like a key and lock type deal with antigens and antibodies? How do we not know that the antibody just conforms to the antigens proportions?

[Ryan_m_b]

if they are impossible to see, how do we know its like a key and lock type deal with antigens and antibodies? How do we not know that the antibody just conforms to the antigens proportions?

Well if the antibody mechanically conformed to the antigen we should see binding on the basis of morphology rather than chemistry, considering all antibodies have pretty much the same physical conformation (but variable chemical regions) it would mean that all antibodies bind to a huge variety of antigens. Conformational changes would make antibody binding far less specific and would still require chemical bonding.

Obviously morphology plays a part but only by providing an appropriate configuration for the correct chemical binding.

Whilst we cannot see with visible light experiments using X-ray crystallography can show antigen-antibody complexes.

[bobze]

if they are impossible to see, how do we know its like a key and lock type deal with antigens and antibodies? How do we not know that the antibody just conforms to the antigens proportions?

Because we can go into a lab and test the idea.

You can build a column with antibodies stuck to the inside and run antigens through it, collecting them at the bottom. The antigens will come out of the column, based on how well they bind on antibodies within the column.

If we look antigens of protein in nature, what we see is that they can bind to antibodies across species boundaries when protein homology is conserved.

For example, if you make rabbit antibodies to say a human protein then use the homologous protein from another species, the antibodies will still bind very well too it, so long as there is conservation of the proteins sequence and structure. If you use a totally unrelated protein, what you find is damn near all of it just passes through the column.