Immunoglobulin elution from multiple sclerosis brain

Immunoglobulin (Ig) was eluted from multiple sclerosis (MS) brain tissue. Razor thin slices of white matter from 10 g of MS and control brains were washed with 5 liters of phosphate-buffered saline (PBS), then treated for 90 sec with acetic acid, pH 2.5, containing Pepstatin and epsilon-aminocaproic acid. The protein concentrations of the PBS washes and neutralized acid eluates were determined, and the eluates were assayed for Ig by competitive microradioimmunoassay using rabbit anti-human F(ab1)2. Successive PBS washes reduced extracellular protein to a very low level. Equivalent quantities of protein were recovered from 7 MS and 6 non-MS brain samples after PBS washing and acetic acid elution. However, the amount of protein needed for 50% inhibition of [125I]IgG binding to anti-human F(ab1)2 was significantly less in MS brain than in non-MS brain (P less 0.05). The Ig in brain eluates was present in the void volume of a DEAE cellulose column. The techniques described above facilitate the isolation and characterization of cell-surface Ig in MS brain.