Chemiluminescence and immune cell activation: general features of the thymocyte chemiluminescent responses to plant lectins.

Rat thymocytes respond to exposure to plant lectins by a burst of oxidant generation as detected by chemiluminescence (CL) (CL) in presence of luminol. All lectins tested were capable of evoking CL as long as sufficiently high concentration was used. There was no correlation between the capacity of a given lectin to evoke CL on one hand and its ability to cause mitogenic transformation or thymocyte agglutination on the other. During the first few minutes following exposure to Con A, cells in the thymocyte pool become committed to CL but once commitment is induced, removal of cell bound ligand by addition of excess methyl-alpha-D-mannoside does not significantly alter the response. Succinylated Con A is as effective as native Con A at lower concentrations but is much more effective at higher concentrations in evoking CL. Thymocyte CL can occur in absence of extracellular calcium but this calcium-independent CL is reduced by the addition of magnesium. In presence of calcium, CL response is greatly augmented and the calcium dependent response is not inhibited in presence of magnesium. The response is relatively radiosensitive. Thymocyte CL response is inhibitable by catalase and scavengers of oxidative radicals but is relatively resistant to the effects of superoxide dismutase, requiring high concentrations of significant effect.