This came in on my pediatrics email newsletter from Medscape.
(http://www.medscape.com).  It's a free service and well worth the
registration, imho.

Anna Swisher
LLL Leader
Austin, TX

Protein Found in Colostrum and Milk Is a B-Cell Mitogen

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WESTPORT, CT (Reuters Health) Jan 16 - Soluble CD14 found in colostrum and
milk promotes B-cell proliferation and differentiation, Canadian and
Japanese researchers report in the January 16th issue of the Proceedings of
the National Academy of Sciences.

To find proteins involved in B cell growth and differentiation, Dr. Michael
Julius from the University of Toronto, and colleagues fractionated bovine
colostrum and isolated a protein that they later determined was equivalent
to soluble CD14. They also found that at nanomolar concentrations, either
native or recombinant forms of the protein led to growth and differentiation
of B cells and antibody secretion.

Since they had used bovine colostrum as a source of soluble CD14, the
researchers assessed the expression of the protein in human mammary
secretions and found that it was enriched 100- to 1000-fold compared with
plasma and persisted for up to 400 days postpartum. Similar results were
found in bovine colostrum and milk.

Lastly, the researchers administered soluble bovine CD14 to neonatal mice,
which induced a transient surge in B cell differentiation 4 days later.

"The results presented establish soluble CD14 as a naturally occurring
soluble B-cell mitogen of mammalian origin," Dr. Julius and colleagues
conclude.

"Based on the described enrichment of soluble CD14 in colostrum and milk, it
is tempting to speculate on its role in actively stimulating the immune
system of the suckling neonate," they add. "It may be involved in the
homeostasis of immunoglobulin M in the developing neonate, and its
demonstrated capacity to synergize with B-cell antigen receptor signaling
may reflect its role in the activation of B cells before the generation of a
full complement of functional helper T cells."

Proc Natl Acad Sci USA 2001;98:603-608.

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