Some time ago, there was a question about a reference for increased
concentrations of immune factors in the milk of "extended" nursers.  I
found the following:  Goldman AS, Goldblum RM.  Immunologic components in
human milk during the second year of lactation.  Acta Paediatr Scand
1983;72:461-2.  They studied the milk from five women at 12, 13-15, or
16-24 months of lactation.  They compared their results to previous
studies (Goldman AS, et al.  Immunologic components in human milk during
the first year of lactation. J Pediatr 1982;100:563-7; and Goldman AS, et
al.  Immunologic components in human milk during weaning. Acta Paediatr
Scand 1983;72:133-4), and found the concentrations of total and secretory
IgA, lactoferrin and lysozyme to be similar to those in the last 6 months
of uninterrupted lactation and during gradual weaning at 6-9 months.  The
concentrations listed were as follows:

COMPONENT               12 MONTHS       13-15 MO        16-24 MO

IgA
        Total           0.8+/-0.3       1.1+/-0.4       1.1+/-0.3
        Secretory       0.8+/-0.3       1.1+/-0.3       1.1+/-0.2

Lactoferrin             1.0+/-0.2       1.1+/-0.1       1.2+/-0.1
Lysozyme                196+/-41        244+/-34        187+/-33

They also found that SIgA antibodies to E.coli were produced during the
second year of lactation, which supported the idea of persistent
functioning of the enteromammary lymphocyte pathway throughout lactation.
Their conclusions were "...partial breast-feeding during the second year
benefits the infant by providing immunologic factors that would otherwise
be unavailable."  Does anyone know if Dr. Goldman or anyone else has done
any further studies in this area?  Alicia.