Elevated levels and different repertoire profile of colostral anti-LPS antibodies may have a significant role in compensating newborn immunity

A high prevalence of systemic infections caused by enterobacteria such as E scherichia coli is observed during the neonatal period. Lipopolysaccharide (LPS) is one of the major factors responsible for septic shock caused by th ese Gram-negative bacteria. We have recently demonstrated the presence of a nti-LPS immunoglobulin (Ig)G antibodies in cord blood with a repertoire ide ntical to that found in maternal serum. In the present study, we analyzed a nti-LPS O111 antibody isotypes in maternal serum and colostrum from mothers and in cord serum from their respective full-term (n = 30) and preterm (n = 13) neonate infants. The main isotype found in serum samples from mothers of term infants was IgM (range between 28 and 54 mg/l), followed by IgA (1 -2 mg/l) and IgG (2-3 mg/l). The range of IgG antibody concentrations in co rd blood was between 2 and 3 mg/l, as a result of placental transfer. A nov el observation in our study was that the LPS bands recognized by colostral antibodies were completely different from those recognized by IgG in serum. Colostral IgA antibodies recognized several bands not bound by serum IgG a ntibodies from the respective maternal serum, independently of the antibody quantity. In addition, we verified the pattern of LPS recognition by serum IgA and colostral IgA antibodies was identical, what suggested that the an tibody isotype found in serum could probably be derived from differentiated IgA-positive cells which were homing to the mucosa through the mucosal hom ing mechanism. Identical pattern of recognition was obtained comparing the IgA and IgM isotypes in colostrum. Slight differences in the pattern of rec ognition were found between colostral and serum IgM antibodies. The fact th at colostral antibodies recognize much more bands than serum antibodies may be important for the host to mount an effective immune response in the int estinal lumen, in order to prevent excessive absorption of LPS, reducing po ssible systemic effects caused by the molecule.