- When an organism looks tolerance to some of its self-antigens (individual’s immune system’s self – not a foreign substance) causes autoimmune diseases 
- Any part of the body can become an antigen, but auto immune diseases are typically linked to certain tissues (image below) 
- This tolerance loss the self-antigens may have been caused by a malfunctioning of the mechanism of the immune system to determine itself from a foreign substance. These can be lead on by a trauma or an infection where tissues that are normally free of the immune system are subjected to lymphocytes. i.e. spinal cord
- Auto immune diseases also vary from person to person because of the vast number of possibilities to develop loss of tolerance to self-antigens. 


Immune system and autoimmune diseases from a biochemistry perspective 

- Antibodies can bind two identical antigens simultaneously however, IgM and IgA are multivalent 
- A foreign substance usually has many antigenic regions – places where antibodies can bind. 
- When the immune system activates, there are many different antibodies made to bind these different antigenic regions
- In this way they can cross link and form a lattice and quickens its breakdown from the immune system (i.e. B cell proliferation). 


Grand Valley State University

- Despite having the conserved immunoglobulin fold motif, immunoglobulins can bind many different types of antigens. 
- Amino acid variations lie at the immunoglobulins antigen-binding site.  


How do antibodies bind different antigens? 

Voet, D., Voet, J. G., & Pratt, C. W. (2013). Chapter 7: Protein Function: Myoglobin and Hemoglobin, Muscle Contractions, and Antibodies. In Fundamentals of biochemistry: Life at the molecular level (4th ed., pp. 176-216). Hoboken, NJ: Wiley. Retrieved February 21, 2021, from archive.org.

Fundamental of biochemistry: Life of the molecular level 4th edition: Chapter 7

Biochemsitry: Stimulating an Immune Response 

- Antigens (foreign substance) stimulate creation of preexisting B cell the antibodies which recognize the antigen. 
- The genes that code for antibodies are limited – so where does the diversity come from? 
- The antibody diversity is accounted from the genetic changes of the B lymphocytes development. 
- Antibodies are coded by DNA segments: V, J and C for the light chains and V, D, J and C for the heavy chains. Because there are so many segments and many versions of these segments are possible, the possibilities for antibodies are significantly large. 
- Additionally, changes occur once a B cell has encourntered an antigen and secrets antibodies. 
- The B cells divide and the antibody gene mutation increases and creates a trial of nucleotides that vary (one amino acid mutations for every cell generation) and this allows for antigen specificity of the antibody to be fine tuned over many cell generations. This antigen-binding affinity increases with the B cell proliferation. 


Learn Before

Related

Learn After