A comparison of the evolution of transmitted IgG immunoglobulin and diphtheria antitoxin titers in the newborn.

The evolution of the titers of transmitted IgG and diphtheria antitoxin was studied in 20 neonates during the first 2 months of life (6 serum samples for each). A rapid fall of the passive IgG titer was observed during the first weeks: as a rule the higher the initial titer the greater the fall. After the 15th day the rate of decline slows down. The evolution of the titer of transmitted maternal diphtheria antitoxin depends also on the initial level, and if it is low it can remain more or less constant for a long time. The initial level of passive IgG does not influence the drop in diphtheria antitoxin titre and vice versa. Therefore, the evolution of total IgG and diphtheria antitoxin levels appear not to be interdependent.