Sequential assay of human milk immunoglobulins shows a predominance of lambda chains.
BACKGROUND
Little is known of the light chains associated to heavy chains in secretions immunoglobulins. We investigated the partition of light chains in a mucosal fluid of easy access and major physiologic importance: human milk.


METHODS
This study provides a sequential analysis of IgA, lambda and kappa chains levels in human milk during the first days of lactation. The levels of IgA alpha-chain and of lambda and kappa light chains of immunoglobulins were assayed in 162 samples of normal human milk collected during the first night of lactation, using a classical immunonephelometric assay. A specific enzyme-linked immunosorbent assay was developed to specifically measure the levels of IgA-linked light chains, yielding similar values. Ten samples of normal human serum obtained from healthy adults were tested in parallel.


RESULTS
The highest levels were observed during the first 3 days of lactation, and a plateau appeared for the three proteins after day 4. Mean lambda chains levels were consistently higher than these of kappa chains, resulting in a reversed kappa/lambda ratio, significantly different from the classical 2:1 serum ratio confirmed with this method on control samples.


CONCLUSIONS
This study indicates that milk immunoglobulins use an unusual partition of light chains, especially in IgA.
Molé
C M
CM
Laboratoire d'Immunologie, Faculté de Médecine de Nancy Vandoeuvre les Nancy, France.
Montagne
P M
PM
Béné
M C
MC
Faure
G C
GC
D006801:Humans; D007071:Immunoglobulin A, Secretory / Q000737:chemistry*; D007145:Immunoglobulin kappa-Chains / Q000378:metabolism; D007146:Immunoglobulin lambda-Chains / Q000378:metabolism*; D007774:Lactation; D008895:Milk, Human / Q000276:immunology*; D013997:Time Factors
D007071:Immunoglobulin A, Secretory; D007145:Immunoglobulin kappa-Chains; D007146:Immunoglobulin lambda-Chains