Inhibition of monocyte spreading. A direct in vitro test for assessing delayed-type hypersensitivity in man.

An expression of delayed-type hypersensitivity to tuberculin was tested in Mantoux positive and Mantoux negative persons. Their lymphocytes and monocytes were isolated from venous blood and incubated in vaseline chambers with or without tuberculin. In the presence of tuberculin, a substantially lower percentage of monocytes from Mantoux positive persons spread, than monocytes from Mantoux negative persons. This antigen-induced inhibition of monocyte spreading seems to be a reliable measure of tuberculin hypersensitivity, since it occurs only in Mantoux positive persons and correlates well with the intensity of the tuberculin skin reaction. Reproducibility of the test and the speed with which it is performed could constitute a basis for the use of monocyte spreading inhibition in clinical studies of cell-mediated immune reactions.