Lisa,
I believe the transplantation study showed the lowest level of organ rejection
between persons breastfed by the same mother (i.e. siblings or half siblings).
 I think the take home message was that breastfeeding modified immune response
to avoid sensitization to the "family antigens" whether a child shared all of
them or not.  There is similar work in transplantation in fetal animals,
before a certain gestational age, transplanted tissue is recognized as "self",
despite genetic/antigenic differences.  Later transplants with the same tissue
type will not be rejected.   It further underscores the immunologic immaturity
of human infants if they can be desensitized to maternal antigens by
breastfeeding.
        Fascinating!
Catherine Watson Genna, IBCLC  NYC  [log in to unmask]