Susceptibility to invasive Haemophilus influenzae type b disease and the immunoglobulin G2m(n) allotype. There has been considerable controversy about the role of the immunoglobulin G2m(n) allotype and risk of invasive Haemophilus influenzae type b (Hib) disease. This allotype was studied in a large cohort of Finnish children (178) with invasive Hib disease. The G2m(n) allotype distribution was similar to that in the normal white Finnish population. No increased risk of Hib disease could be associated with the n-/n- genotype [i.e., lack of G2m(n) allotype]. Thus, the G2m(n) allotype does not seem to be a major determinant of susceptibility to Hib infection among white populations in industrialized countries. 