Lymphocyte-Retrobulbar Fibroblast Interaction: Mechanisms by Which Stimulation Occurs and Inhibition of Stimulation

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Abstract

Mechanisms by which lymphocytes stimulate glycosaminoglycans (GAG) production and glucose utilization by cultures of retrobulbar fibroblasts were investigated. Lymphocytes must be living or undergo at least one day of preincubation before freeze-thawing to be active. Preliminary exposure of lymphocytes to phytohemagglutinin for one day inconsistently induced small increases in the lymphocyte potency. Prolonging exposure of the lymphocytes to phytohemagglutinin to three days resulted, in decreased potency. However, Mitomycin C, an inhibitor of lymphocyte blastogenesis, significantly enhanced the potency of lymphocytes subsequently treated with phytohemagglutinin for one day. Lymphocytes, whether treated with phytohemagglutinin or not, had no definite effect on fibroblast proliferation. Cyclic-adenosine 3',5'-monophosphate in concentrations up to 12.7 x 10^-4M had no effect on the fibroblast metabolism. Sodium fluoride, 10^-4M also had no effect on the fibroblast cultures but at 10^-2 M inhibited all metabolic parameters evaluated. In contrast, theophylline, 5.6 x 10^-4M, stimulated GAG production but had no effect on glucose utilization or proliferation by the fibroblasts. The theophylline effect was additive to the stimulation by lymphocytes at submaximal doses. It appears that the stimulating activity of lymphocytes on retrobulbar fibroblasts, although dependent on in vitro incubation, is not related to blasto genesis. The adenyl cyclase system is not involved in the stimulation of fibroblasts; the enhancement by theophylline of GAG production may occur by some other metabolic pathway. Hydrocortisone inhibited the lymphocyte stimulation of GAG production by fibroblasts but had no effect when preincubated with lymphocytes and had a slight and insignificant inhibitory effect on the basal GAG production by the fibroblast cultures. There was no definite effect of hydrocortisone on glucose utilization and cell proliferation by lymphocyte-stimulated fibroblasts.