DETERMINATION OF PARAMETERS THAT CHARACTERIZE EFFECTOR-TARGET CONJUGATION OF HUMAN NK AND LAK CELLS BY FLOW-CYTOMETRY

Effector-target conjugation between different cell populations of huma n NK cells and K562 tumor cells has been studied from binding isotherm s obtained from data of effector (alpha) and target (beta) conjugate f requencies measured by flow cytometry analysis at different effector-t o-target ratios. Non-linear and linear regression methods were applied to these isotherms to calculate the binding parameters that character ize the process of conjugation, namely, the maximum effector and targe t conjugate frequencies, the dissociation constant of the conjugates f ormed, the binding units and the area under the binding isotherms. The results obtained show that: (1) flow cytometry analysis of effector-t arget conjugation is faster, unbiased and more suitable than microscop ic counting of conjugates, thereby permitting the analysis of larger n umber of conjugates in shorter times, (2) the binding parameters deriv ed from conjugate frequencies obtained by flow cytometry analysis diff er from those obtained by microscopy, (3) the discrepancies between th e two methods are due to the presence of several cells engaged in mult icellular conjugates that are detected as single particles by flow cyt ometry and (4) the analysis of population distributions of the conjuga tes formed at different values of the effector-to-target ratio permit the above discrepancies to be corrected. (C) 1997 Elsevier Science B.V .