Thursday, January 8, 2015

The Role of Endogenous Retroviruses in B Cell Immune Response to Foreign Antigens

Over the course of evolution, retroviral infections have left remnants of their genetic footprint imprinted within the human genome.  This is believed to play such an important role in human biology that the collective genomes from viruses that innocuously inhabit the human body is referred to as the virome.

The virome is a part of the larger community of microbiota that shares a commensal or symbiotic relationship with the human body.   Important participants in this community are the gut microorganisms that collectively breakdown food, produce important nutrients, inhibit the growth of deleterious organisms and stimulate immune responses.

The immune reaction to an invasive organism typically results in the production of specific antibodies by circulating B cells in response to antigens presented by the offending organism.  There are two arms to B cell involvement – one involving T cell dependent (TD) processes and the other a T cell–independent (TI) response.   This latter response is elicited through the innate immune sensing pathways in antibody production through specific B cell receptor (BCR) cross-linking
Dr. Ming Zeng and his colleagues at the Center for the Genetics of Host Defense at the University of Texas Southwestern Medical Center in Dallas, Texas studied the involvement of endogenous retroviruses (ERV) in innate immune pathways.

In the course of their investigation, they exposed mice to protein molecules ordinarily found on the outer membranes of invasive bacteria and viruses.  These proteins are known to invoke the TI-mediated B cell response.   What they discovered was that immunization with these antigens resulted in the enhanced production of endogenous retrovirus (ERV) RNAs in the responding B cells.  Furthermore, this response apparently triggered a sustained reaction against the specific antigens through enhanced immunoglobulin M production.

These findings are of particular interest, for they offer further validation for the role of endogenous retroviruses in the immune response to invasive and deleterious microorganisms.  A well-functioning immune system is absolutely essential for the individual life of the organism and has been perfected during the evolution of life on the planet.