Normal values for free light chains in serum different age groups.

The concentration of free light chains from the immunoglobulins was measured in twelve paired sera from mothers and newborns and from 149 sera from normal individuals in various age groups. Variations in concentration during life are correlated to the variations in the concentration of 'regular' immunoglobulins. A concentration of light chains in cord blood of 35% of mean normal adult level (MNA) together with a rapid passage of light chains across the placenta is interpreted as indicating catabolization of maternal light chains in the fetus. This is further supported by the finding of a lower concentration of light chains in maternal serum than in normal adult serum. The investigation shows that the concentration of light chains falls rapidly from 35 to 24% of MNA during the first few days of life. From the first week of life the concentration of light chains increases and low normal adult values are attained by one year of age. Except for difference in concentration, the elution pattern for light chains from Sephadex G-100 columns was similar for normal, adult and cord blood. The relationship between kappa and lambda chains--the K/L ratio--is 1.2 for normal and maternal serum and 1.0 for cord serum.