A sensitive technique for measuring specific macrophage aggregation: a comparison with macrophage migration inhibition, for the detection of lymphokine activity.

A new quantitative method for the measurement of macrophage aggregation, induced by lymphokine preparations, is described. This involves the continuous measurement of the light absorbance of stirred macrophage suspensions. The results have been compared with those obtained by measuring macrophage migration inhibition activity for the detection of lymphokine activity. Separation of crude lymphocyte culture supernatants by Sephadex G-200 shows that the material with aggregating activity is heterogeneous. The greater amount of this activity is not separated from macrophage migration inhibition activity, and has a molecular weight of 35,000--70,000. A comparison has been made with other published methods for measuring macrophage aggregation.