How HIV outmaneuvers the immune system

T cells and antibody-producing B cells carry out immune defense against specific pathogens such as viruses. Antibodies and T cell receptors are highly diverse molecules that can recognize millions of different molecules. Upon encounter of a foreign antigen (such as a molecule from the surface of a virus), T cells and B cells whose receptors match that particular antigen expand dramatically, providing the immune system with a large number of very specific defenders. After an attack is fought off, the overall numbers of specific T and B cells go down again, but a few of them become long-lived so-called “memory cells” that ensure a quick re-mobilization should the same type of attacker strike again.

T cells consist of two major groups: CD4-positive T helper cells (who help other immune cells in mounting an effective response) and CD8-positive killer T cells. HIV infects and destroys CD4-positive cells, leaving patients with a crippled immune system. Throughout the course of HIV disease, however, patients have high levels of HIV-specific killer T cells. Early after initial infection, these cells are able to effectively kill the virus and reduce viral load. On the other hand, during the later stage of disease killer T cells, while still present, seem no longer able to control the virus. In an article in the November 4 issue of the Journal of Clinical Investigation, Premlata Shankar and colleagues from the Center for Blood Research at Harvard Medical School suggest why this might be the case.

The researchers compared killer T cells from HIV infected asymptomic individuals with those from symptomatic AIDS patients. They examined the killer cells’ ability to eliminate target cells infected with laboratory strains of HIV on one hand, and with autologous virus (isolated from the patient) on the other. What they found is that killer T cells from asymptomatic individuals can recognize and kill both types of target cells. In contrast, the killer T cells from symptomatic patients, while still able to recognize and eliminate the laboratory strain targets, no longer killed target cells that were infected with their own, autologous, virus. This is likely due to the virus’ propensity to mutate and the in inability of the patient’s weakened immune system to keep up with the changing virus.

These results demonstrate that the high number of HIV-specific killer T cells found in AIDS patients are remnants of what used to be an effective response early after infection but no longer recognize the mutated autologous virus. Moreover, these findings reveal that conventional assays to measure killer T cell responses in HIV patients–which focus on responses to laboratory strains–do not accurately reflect but overestimate the response to the patient’s autologous virus.

CONTACT:
Premlata Shankar
Harvard Medical School
The Center for Blood Research
800 Huntington Avenue
Boston, MA 02115
USA
PHONE: 617-278-3476
FAX: 617-278-3403
E-mail: shankar@cbr.med.harvard.edu

Media Contact

Brooke Grindlinger EurekAlert!

Weitere Informationen:

http://www.jci.org/

Alle Nachrichten aus der Kategorie: Health and Medicine

This subject area encompasses research and studies in the field of human medicine.

Among the wide-ranging list of topics covered here are anesthesiology, anatomy, surgery, human genetics, hygiene and environmental medicine, internal medicine, neurology, pharmacology, physiology, urology and dental medicine.

Zurück zur Startseite

Kommentare (0)

Schreib Kommentar

Neueste Beiträge

How Stable is the Antarctic Ice Sheet?

Scientists from Heidelberg University investigate which factors determine the stability of ice masses in East Antarctica. As temperatures rise due to climate change, the melting of polar ice sheets is…

Smart sensors for future fast charging batteries

European project “Spartacus” launched Faster charging, longer stability of performance not only for electric vehicles but also for smartphones and other battery powered products. What still sounds like science fiction…

Small molecules control bacterial resistance to antibiotics

Antibiotics have revolutionized medicine by providing effective treatments for infectious diseases such as cholera. But the pathogens that cause disease are increasingly developing resistance to the antibiotics that are most…

Partners

By continuing to use the site, you agree to the use of cookies. more information

The cookie settings on this website are set to "allow cookies" to give you the best browsing experience possible. If you continue to use this website without changing your cookie settings or you click "Accept" below then you are consenting to this.

Close