Immune Defense Against Viruses Not Based On Antibody Production, Study Says
A new research comes with a new explanation for immune defense against certain viruses. According to a study published on March 1st in the journal Immunity, the connection between the specific immune system and nonspecific immune system is crucial when it comes to defense against certain viral infections. This fact suggests that antibodies are not an essential component of the immune system as it was previously thought.
Immune system relies on two types of mechanisms: innate immunity and acquired immunity. Innate immunity forms the first line of defense against infection. It is very important to note that this type of immunity is inherited from parents and can not be changed until the end of life. Also, innate immunity is antigen independent and has no immunological memory. Cells that play role in innate immunity are the polymorphonuclear cells (PMN), macrophages, complement system, natural killer cells (NK) and dendritic cells. The defense mechanisms of innate immunity are anatomical barriers (skin, mucosa), enzymes, body temperature, and others.
Acquired immunity is selective and is directed against the triggering agent, that is against the antigen. The cells that participate to this type of immunity are T lymphocytes, B lymphocytes and antibodies.
The senior study author, Dr. Ulrich H. von Andrian, from Harvard Medical School, explained that, even in mice infected with vesicular stomatitis virus (VSV) that presented a high concentration of anti-VSV antibodies in their system, the infection still managed to invade the central nervous system fatally.
Researchers studied VSV infection in mice that have B lymphocytes but no antibodies. Even if B cells were essential to mice survival after exposure to the VSV, they did not require any specific antibodies. B cells produce a substance that activates macrophages and macrophages in turn produce type I interferon, essentially in killing the virus.
VSV is a virus belonging to family Rhabdoviridae. VSV is in fact an arbovirus , that is transmitted by insect bites and infected mammalians. Therefore, the risk of being exposed to such a virus is higher among farmers. People infected with VSV present flu-like symptoms.
The study provides a new explanation on how the immune system functions against fatal infections such as rabies virus. Moreover, the research shows that B cells do not play a major role in acquired immunity against the virus but are related to innate immunity. Dr. von Andrian, pointed out that this new finding contradicts current opinion according to which antibodies are essential for survival after an viral infection such. In addition the study highlights a new B cell function (activation of macrophages).
Future studies aim to shed light on the role of antibodies and interferon in fatal infections such as West Nile virus and rabies.