[Importance of studying deficiencies of IgG subclasses (IgG2 and IgG4) in immuno-allergologic practice].

Levels of the sub-classes of immunoglobulins IgG2 and IgG4 have been established by radial diffusion with monoclonal antibodies in 150 subjects. 49 (42 adults and 7 children) showed either a low level of IgG2 (less than 0.42 g/l n = 11) or a reduced level of IgG4 (less than 0.05 g/l n = 38). A single patient had a double deficit, 38 subjects had a superinfection of which 17 had a severe form and in 77% of these cases a level of IgG4 of less than 0.05 g/l.