THE IMMUNE SYSTEM - evolved over time to protect
organisms from the threat of perceived antigen. All animals have an immune system.
Antigens are anything that might harm the organism and the immune system usually recognizes them as a protein that's shape binds to a receptor on a white blood cell. The immune system will usually manufacture complimentary shaped antibodies to attack the antigen by sticking to and then clumping them (pus is formed this way). Most antigens are the surfaces of a virus, bacteria, fungus parasite (pathogens), or unfortunately the tissue of a foreign graft of tissue such as donated blood or organs such as a kidney or heart.
On occasion a person's immune system will perceive self proteins as antigen and generate an autoimmune attack. Diabetes 1, lupus some arthritis, multiple sclerosis, Crone's disease are a few examples of diseases  caused  by autoimmunity (self immune attack).

The main players of the immune system are the white blood cells or lymphocytes of which there are many types which produce antibodies and can remember previous challenges to the the immune system (the basis of vaccination) as well as proteins called compliment which we will not elucidate in our course!

The leucocytes or WBCs are the major players in the immune system.

All are produced from stem cells in the Hemopoietic system, the bulk of which lies within the marrow of long bones.  The WBCs travel throughout the tissues of the body and take fast tracks by traveling in the lymphatic system.
 


 
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The HIV virus gains access to the T4 (helper "T") lymphocyte by attaching to the CD4 cell marker.
The virus then enters the cells and because it is a Retro virus it uses reverse transcriptase to create new DNA that becomes part of the host cell's nuclear DNA!!!
The viral DNA instructs the T4 cells to create new viruses and terminating its usefulness in the immune system and killing it later.
Because the T4 lymphocyte is key to the orchestration of the immune system function (it acts like a general in an army conducting the actions of other WBCs via lymphokines (hormone like in nature).
                    AIDS DRUGS
One of the key drugs in the AIDS drug cocktail that is used is Zidovudine commonly know as AZT.
AZT is a faulty analogue of thymidine which when inserted into a replicating strand of DNA during virus synthesis cannot link to the next nucleotide. This effectively reduces viral replication.
NOTE the 3' carries an amine group that will not link to another nucleotide.

Fortunately AZT is used by the HIV preferentially during reverse transcription  than by cells in the human body!!! (although some harm is felt)
Regardless of the amazing science involved in the researching of pharmaceuticals this disease will only be eradicated through education, awareness, and subsequent modification of human behavior.