Human uropod bearing lymphocytes: Isolation of a factor from human milk that abrogates the uropod inhibitory protein from human serum

Summary

Previous studies have demonstrated a factor from human serum or plasma that regulates uropod formation in peripheral blood thymus-derived lymphocytes. This study describes the isolation and partial purification of a factor from colostrum and mature human breast milk that abrogates the uropod inhibitory protein (UIP) of serum. The antagonist is protein in nature since trypsin and protease destroy the activity. Thermal inactivation experiments indicate a relatively heat stable protein with complete inactivation occurring only after heating at 75° C. Gel filtration of the milk antagonist on Bio Gel A 15 M demonstrated a peak of biological activity in the void volume indicating a molecular weight of greater than 15 × 10⁶ daltons. The milk antagonist is not associated with the cream fraction of milk or with the acid precipitable casein fraction. Finally, the antagonist could be neutralized with anti-whole human milk in a dose dependent fashion. The physiologic role of this antagonist is not known; however, the ability to regulate lymphocyte deformability suggests that the protein may be important in controlling the traffic of lymphocytes to the mammary gland.