Can someone set me straight on conditions/antigens which induce
tolerance when taken orally as opposed to those capable of eliciting an
immune response? I have long understood that most antigens taken
orally lead to tolerance (thus the basis of "feeding" MBP to EAE mice
and thus relieving autoimmune reactions)...Of course there are
conditions under which a "protective" response can be elicited when
antigen is encountered orally (sabin live attenuated polio vaccine for
example)....I had assumed the critical difference was that the polio
vaccine was alive and thus capable of penetrating the mucosal lining
and also capable of generating a transient infection...But now I am
confused by a recent paper that appeared in Science (May 5,
1995/vol.268) regarding antigens expressed in plants. When "fed" to
mice, IgA annd IgG specific to the cloned antigen were indeed elicited.
There is even a News & Views article in the May 5 Science touting the
great potential of oral vaccines grown in plants....even discussion of
"feeding" babies "banana vaccines"...my first impression is that such
an approach could be potentially dangerous should tolerance be induced
instead of immunity, particularly when fed to infants....Your comments
would be greatly appreciated!
Monica Ranes-Goldberg, Ph.D.
Immunology Instructor
UC Berkeley Ext.
