[A new genetic marker for human IgG3 linked to factor Gm (21) in caucasian and mongoloid populations].

A new antigenic determinant Gm (L 1) was shown to be present on protein IgG, Gm (21) but absent on protein IgG, Gm (5). It was found present in a French family and in an Algerian family where it was transmitted with the Gm (1) and Gm (17). In caucasian and mongoloid populations it is usually associated with Gm (21) but dissociated in negroids.