A study of cells present in lymph draining from a contact allergic reaction in pigs sensitized to DNFB.

The binding of the third component of the complement system (C3) to Con-A-stimulated murine spleen cells (MSPC) and the role of C3 for the formation of cell aggregates was examined. C3 became bound up to 15% of the T blasts (Thy-1.2 positive cells) while only 2.5% of the non-activated T cells bound C3 when they were incubated with autologous serum. Application of purified human C3 or heat-inactivated autologous serum did not result in a detectable C3 binding. The highest percentage of C3-carrying T blasts (15% of Thy-1.2 positive cells) was observed concomitantly with maximum ³H]-thymidine incorporation when cells were harvested between 24 and 38 hours of culturing. Treatment of the Con-A-stimulated MSPC with phenylmethylsulphonylfluoride (PMSF) and soybean trypsin inhibitor (SBTI) induced a decrease of the percentage of C3-binding T blasts. However, at small concentrations the protease inhibitors (PI) effected increased C3 binding depending on the time of harvesting the cells. The PI when applied in concentrations causing an enhancement of the percentage of C3-positive T cells also increased the aggregation of Con-A-stimulated MSPC. In contrast Con-A-stimulated MSPC aggregated less when treated with autologous mouse serum containing anti-mouse C3. These observations suggest that the cell contact among Con-A-stimulated MSPC in the presence of serum is at least in part mediated by C3 bound to T-cell blasts. Based on these and previous findings that certain concentrations of DFP enhance rosette formation of blast-transformed B cells with EAC1423b, we hypothesize that PI are involved in regulation of B- and T-blast membrane metabolism, thereby influencing C3-deposition on T-cell blasts and C3-dependent cell—cell interaction.