RADIOIMMUNOMETRIC QUANTIFICATION OF SURFACE LACTOFERRIN IN BLOOD MONONUCLEAR-CELLS

A radioimmunometric method was developed for the quantification of lac toferrin molecules natively bound to blood monocyte and lymphocyte sur faces and the estimation of the surface lactoferrin-binding capacity o f these cells after their incubation with exogenous lactoferrin. Value s of surface lactoferrin obtained were greatest for monocyte-rich isol ates (9,168 +/- 1,713 molecules/cell; n = 19). The values of monocyte surface lactoferrin for males were similar to those of premenopausal f emales (8,980 +/- 2,378 (n = 8) and 9,427 +/- 2,606 molecules/cell (n = 11), respectively), but males had slightly lower values of monocyte surface lactoferrin binding capacity than did premenopausal females (1 0,447 +/- 2,478 molecules/cell versus 15,958 +/- 3,731 molecules/cell, respectively; p > 0.05). Expressed as saturation of the monocyte surf ace lactoferrin binding capacity, values of 97.2% +/- 22.6% for males and 76.6% +/- 14.3% for females were calculated. Intermediate values o f surface lactoferrin were found in B-lymphocyte-rich isolates from fi ve patients with B-cell chronic lymphocytic leukemia. In T-lymphocyte- rich preparations, there were low levels of native lactoferrin express ion (154 +/- 63 molecules of lactoferrin/cell; 3 isolates). The presen t technique should permit additional quantitative studies of mononucle ar cell surface lactoferrin to determine the role of lactoferrin surfa ce binding and analyses of factors that modulate this binding.