Differential effects of human granulocytes and lymphocytes on human fibroblasts in vitro

Abstract

Polymorphonuclear leucocytes (PMN) were found to damage human fibroblast monolayers. Allogeneic and autochthonous PMN were equally efficient and monolayer destruction (plaque-formation) occurred within 24 hr, as a rule, in the absence of agglutinating substances such as phytohaemagglutinin. Living PMN were not necessary for plaque-formation, since cells heated to 56°C for 30 min or disintegrated by ultrasound were still competent to produce plaques. It is suggested that enzymes enclosed in cytoplasmic granules in the PMN are responsible for plaque-formation. Although the monolayer was destroyed, the target cells were not killed after treatment with PMN, but detached from the surface of the culture vessel into the medium and could be recultivated from the supernatant. Heparin, chondroitin sulphate and trypan blue suppressed plaque-formation by intact and disintegrated PMN, while a variety of metabolic inhibitors or X-rays had no effect.

Lymphocytes from non-immunized donors were also competent to cause destruction of fibroblast monolayers, but this reaction required the presence of phytohaemagglutinin. Heating of the lymphocytes to 48·5°C or ultrasound disintegration abolished the plaque-forming ability, suggesting that living lymphocytes were required. In contrast to PMN, lymphocytes were shown to kill the target cells. PHA-treated lymphocytes were equally cytotoxic to allogeneic and autochthonous fibroblasts and it is suggested that actual target destruction is immunologically non-specific and caused by transformed lymphocytes, which acquire the ability to kill all fibroblast targets regardless of their genotype and the event triggering lymphocyte transformation.