werner@aecom.UUCP (Craig Werner) (06/07/85)
First, let me explain what HLA is. HLA stands for Human Leukocyte Antigen, although they are a group of proteins that occur on every cell in the body. There are 4 groups - HLA-A,B,C are found on every cell. HLA-D is particularly prominent on White Blood Cells. There are hundreds of types of each letter - so many in fact, that probably no two people on Earth (except identical twins) have the same arrangement. HLAs are also known as Transplantation antigens -- they are the cause of Rejection following Heart/Kidney/etc. transplant. One of them - HLA-D4 has been shown to react with the antibody to the virus that presumably causes AIDS. This is the first case of a true False Positive with known cause. Therefore, people who carry the HLA-D4 gene will register a positive result to the AIDS blood test, whether or not they have been exposed to the AIDS virus. However, it can be checked via other means. One explanation for the phenomenon is that the only cell line in which HTLV-3 will grow carries the HLA-D4, and hence the antibody is raised to a HLA-D4/HTLV-3 hybrid (also known as a virally-altered self) and then will react with each component separately. -- Craig Werner !philabs!aecom!werner "The world is just a straight man for you sometimes"
werner@aecom.UUCP (06/11/85)
I realized that in my desire to simplify, I may have mislead, so here is a quick clarification. The Test checks for antibodies against HTLV3, also known as AIDS Related Virus, or anti-HTLV3 antibodies. The article described the testing of anti-HLA antibodies (which are normally used in tissue typing for transplants) and the discovery that one, anti-HLA-DR4, reacted with anti-AIDS antibodies. I left out the 'anti's last time and here's where I made the boo-boo. People who have the HLA-DR4 gene will not test false positive for HTLV3. For them to have anti-DR4 antibodies would mean that they would be attacking their own tissues. The only way someone would have those antibodies was if they had recieved a transfusion or a transplant or a skin graft from someone who had HLA-DR4, or if there's still yet another cross-reacting antigen that hasn't been described yet. I feel much better now. Sorry for the inconvenience and confusion. Craig Werner !philabs!aecom!werner "The world is just a straight man for you sometimes" -- Craig Werner !philabs!aecom!werner "The world is just a straight man for you sometimes"