ACTIVATED HUMAN GAMMA-DELTA T-LYMPHOCYTES EXPRESS FUNCTIONAL LACTOFERRIN RECEPTORS

Lactoferrin (Lf) an iron-binding protein in milk, mucosal secretions a nd neutrophil granules has bactericidal properties and is a source of iron for breast-fed infants. In this paper the authors show that most in vivo activated lymphocytes, i.e. freshly isolated lymphocytes from first trimester human decidua, and most in vitro activated human blood lymphocytes, express lactoferrin receptors (Lf-R), while unstimulated blood lymphocytes do not. All major lymphocyte subsets, i.e. alpha be ta T cells, gamma delta T cells, CD8(+) T cells, CD4(+) T cells, B cel ls and NK cells, express Lf-R after activation. The proportion of Lf-R expressing activated gamma delta T cells is significantly larger than that of activated alpha beta T cells. Lf-R and transferrin receptors (Tr-R/CD71) show the same kinetics of appearance on activated blood ly mphocytes and are, to a large extent, expressed on the same cells. How ever, 35% of decidual lymphocytes and 15% of activated blood lymphocyt es express Lf-R only. Addition of Lf to cultures containing an optimal concentration of Tr augments the proliferative response to polyclonal T cell activators and alloantigens, suggesting that presently used st andard culture conditions for in vitro activation are suboptimal in pa rticular for gamma delta T cells. Lf-R on decidual lymphocytes contain bound Lf, which probably is produced locally. The results suggest tha t Lf is a growth-supporting factor, especially important in local immu ne responses in the mucosa.