What is HLA?

HLA molecules provides immunological unique identification to humans that modulates immune response with external and internal variables. Learn more about HLA here: http://en.wikipedia.org/wiki/Human_leukocyte_antigen

External variables are infectious agents (viruses, bacteria, fungi, parasites), food, foreign tissue, drugs and etc. Internal factors are tissue modification due to infections, cancer and physical trauma (heat, cold etc). Learn more here: http://en.wikipedia.org/wiki/Antigen_presentation