Word: cd4
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Dates: during 1990-1999
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Since 1984, investigators have known that HIV assaults the cells of the immune system by latching on to a protein "receptor," named CD4, found on the cells' surface. When an invader attacks the body, the CD4 molecule normally helps mobilize the immune system's defenses. In this case, though, HIV fools the CD4 receptor into allowing viral particles into the cell. Hovanessian reported last week that his team had found a second receptor, called CD26, that helps the virus enter the cell after it has attached itself to CD4. If Hovanessian is correct, scientists might be able to devise drug...
...many other prominent researchers attending the conference, including Robert Gallo of the National Cancer Institute in Bethesda, Maryland, did not seem at all convinced that a cure was any closer. Gallo, among others, has failed in efforts to design an effective treatment based on the original discovery of the CD4 receptor. After Hovanessian's talk, Gallo tried to avoid reporters but was finally cornered. "Why is the press so excited about this?" he demanded. "I'm flabbergasted. I thought it was an interesting presentation, but I can't say more than that." Gallo's lack of enthusiasm was + hardly surprising...
Their investigation begins with a white blood cell called CD4. It is the linchpin of the immune system and the main target of HIV. As a general rule, people who become infected by HIV suffer a drop in their CD4 count from a normal level of about 1,200 cells per 1/1000th of a mL of blood to 500 cells or less. The risk of developing one or more of the illnesses associated with AIDS rises dramatically if the CD4 count drops below...
...most striking things about the healthy survivors is that after the initial drop, their CD4 count stabilizes -- usually above 500. Assaulted but not overwhelmed, they no longer lose any ground against HIV. One possible explanation is that these men were exposed to a strain of the virus that is naturally weaker than most. The immune system subdues the less malevolent virus, allowing the body to fend off any new attacks by more dangerous strains. In the same way, English milkmaids who suffered from cowpox in the 18th century developed an immunity to the disease that also protected them against...
...most surprising findings has been the discovery of a subset of healthy, long-term survivors who have lived for years with CD4 counts less than 200. For the most part, they do not develop the secondary infections that are associated with AIDS, or if they do, they tend to recover. This only goes to prove that there is a lot about the immune system that immunologists still do not understand. Some researchers believe these men managed to press other white blood cells into service to make up for the CD4 deficiency...