Studies on mechanisms of immobilization of mononuclear cells in the delayed hypersensitivity (DH) reaction

Migration inhibitory (MI) activity in exudates, and migration and inhibition of migration of exudate cells was investigated in the delayed hypersensitivity (DH) reaction induced by intrapleural injection of PPD into complete Freund's adjuvant(CFA)-sensitized guinea-pigs. During the initial reaction (6-hour), two types of antigen-dependent MI activity were detected in serum and cell free exudate. One was a high molecular weight material associated with immunoglobulin, and the other was a low molecular weight material and appeared to be so-called antigen-dependent migration inhibitory factor (MIF). As the reaction progressed (i.e. 12–24-hour), two types of antigen-independent MI activity were revealed in exudate, but not in serum. One of these was a high molecular weight material, and the other was a low molecular weight material and thought to be socalled antigen-independent MIF.Similar experiments were performed on the reversed passive Arthus (RPA) reaction in the pleural cavity of guinea-pigs. A high molecular weight substance having MI activity was detected in 6-hour cell free exudate and was found to be antigen-independent. So-called MIF was not found in this reaction.Migration of unseparated exudate cells from the 18-hour DH reaction was less extensive than that of 6-hour unseparated cells. Addition of antigen caused further inhibition, the effect on 18-hour exudate cells being more pronounced. These results were further examined, using mononuclear cells separated on a Ficoll-Isopaque gradient. The migration area of the mononuclear cells was reduced as the DH reaction progressed. Mononuclear cells from the DH reaction gave a smaller migration area throughout the reaction in comparison with blood mononuclear cells. The migration area of the RPA exudate mononuclear cells was also reduced as the reaction progressed. However 6-hour RPA exudate mononuclear cells gave a larger migration area than blood mononuclear cells.The migration of mononuclear cells from DH exudate was inhibited by addition of antigen. A greater degree of inhibition of migration was induced by addition of antigen to mononuclear cells from 18- and 24-hour exudate cells in comparison with 6- and 12-hour exudates. The migration of mononuclear cells from normal blood (i.e. unsensitized animals) and RPA exudate (6- and 18-hour) was unaffected by addition of antigen. Similar results were obtained for blood of complete Freund's adjuvant sensitized animals from 0- to 18-hour.Adherent (A) and nonadherent (NA) mononuclear cells from 18-hour DH exudate were separated through a glass bead column. The migration of adherent cells from 6-hour exudates was not significantly inhibited whereas that of 18-hour mononuclear cells was markedly inhibited. The effect on migration of each mononuclear cell fraction was detected by mixing with peritoneal exudate cells (used as indicator cells). The effect of the A cells from 18-hour mononuclear cell exudates on peritoneal exudate cells was strong, whereas that of 6-hour exudates was less marked. A similar effect was observed with NA cells, from 6- and 18-hour exudate, on the migration of peritoneal mononuclear cells.