Digestion of bovine αs1-casein with bovine trypsin
produced peptide(s)
with an inhibitory effect on concanavalin A-induced proliferation of mouse
spleen
cells. One of these peptides was isolated from the αs1-casein
digest following
ultrafiltration, hydroxyapatite chromatography and reversed-phase HPLC,
and
amino acid composition and sequence analyses showed it to be sequence 59–79
from
the phosphoserine-rich region of αs1-casein. The isolated
peptide significantly
inhibited the concanavalin A-induced proliferation of mouse spleen cells
and rabbit
Peyer's patch cells, whereas it enhanced the lipopolysaccharide- and
phytohaemagglutinin-induced proliferation of both cells. The
peptide displayed mitogenic activity
in the cell cultures without the commercial mitogen, and significantly
enhanced
immunoglobulin production. Moreover, residues 1–25 from the phosphoserine-rich
region of bovine β-casein had a similar effect on the proliferation
of mouse spleen cells
and rabbit Peyer's patch cells stimulated or not stimulated by the
commercial
mitogen. These results indicate that caseinophosphopeptides may act as
a humoral
immunostimulator in cell cultures.