Humoral immune responses within the human central nervous system following systemic immunization.

We investigated sequential humoral immune responses in the CSF and blood of 6 stable multiple sclerosis (MS) patients without decreases in the blood-brain barrier. Anti-tetanus toxoid antibodies (anti-TT Ab) increased to a similar relative degree within the CSF and blood starting within 2 weeks after subcutaneous booster injection of TT. In 3 of 4 subjects, CSF lymphocytes obtained at 2 weeks secreted anti-TT Ab to the same degree as autologous blood lymphocytes when cultured with pokeweed mitogen. These findings suggest a prompt antibody response within the CSF to systemically administered antigen, not due to diffusion from the serum, with active trafficking of TT-sensitized lymphocytes into the central nervous system.