Measurement of K cell activity: Use of human OR1R1 red cells and anti-D to study the role of different leukocytes as effector cells

Abstract A method for quantitative assay of K cell activity (KCA) with an allogenic combination of human OR 1 R 1 red cells and anti-D (IgG, incomplete antibody) as target cells is described. Lymphocytes alone have been shown to cause lysis of these target cells. Fc receptor-bearing lymphocytes appear to be the chief mediators of KCA. This sub-population is a heterogeneous mixture of sub-sets of other sub-populations defined on the basis of different surface markers and likely to show variable expression of Fc receptors by the EAγ rosette method. Monocytes and neutrophils (and possibly eosinophils), most of which bear Fc receptors, are ineffective as effector cells. Monocytes may in some instances have an inhibitory effect on the expression of KCA of lymphocytes. The method described has the advantage of simplicity (easy availability of OR 1 R 1 cells and anti-D) and a high degree of sensitivity (marked lysis at low L/T ratio) and appears suitable for routine use in clinical practice.