Protection of mice against tick-borne encephalitis by different classes of immunoglobulins

The protective capacities of IgM and IgG immunoglobulins from fractionated human or mouse sera were investigated in tests with tick-borne encephalitis virus. Mice were resistant to challenge with tick-borne encephalitis virus if previously inoculated with specific immunoglobulins but not nonspecific immunoglobulins. The protective ability of IgM, whether derived from mouse or human sera, was only about 1/40 of that of IgG preparations adjusted to the same haemagglutination inhibition or neutralising titres.