Although the central nervous system (CNS) is thought to be immunoprivileged, 
under special circumstances it can produce antibody. Antibody production within 
the CNS, called intrathecal antibody production (ITAbP), is a prominent feature 
of neurological infections and inflammatory diseases, and is thought to possibly 
contribute to disease in multiple sclerosis (MS), but it has not been 
extensively studied. We investigated ITAbP in a viral model of MS. ELISpot, 
real-time RT-PCR for IgG mRNA in CNS tissue, and CSF analysis were used to 
assess ITAbP in two types of SJL mice infected with one of two strains of 
Theiler's murine encephalomyelitis virus (TMEV). The amplitude of ITAbP 
increased during the first 4 months of infection. TMEV viral load remained high 
during the course of the infection, which likely was the main stimulus for 
ITAbP, since within samples of infected CNS tissues, levels of IgG gene 
expression were highly correlated with viral RNA levels, and a large percentage 
of intrathecally produced antibody was directed against TMEV. This study 
provides the first extensive analysis of ITAbP in TMEV infection, and 
demonstrates that, in this animal model of MS, antibody production within the 
CNS is likely driven by the presence of the causative pathogen.