Stimulation of lymphocytes with proteolytic enzymes

Abstract

This chapter describes stimulate of lymphocytes with proteolytic enzyme. Proteinases such as trypsin, plasmin, and others, stimulate lymphocytes in short-term cultures. With murine spleen or lymph node cells, it has been established that proteinases are polyclonal B cell activators inducing blast transformation, increased thymidine incorporation, differentiation into immunoglobulin-producing cells and replacing T lymphocytes as determined by standard methods. Proteinase preparations by themselves might contain endotoxins that stimulate lymphocytes. The best way to check for interference of endotoxins is to use specific proteinase inhibitors, which should neutralize completely the effect of the enzyme. Some less purified commercial preparations of soybean inhibitor have lectin-like activities and cannot be used in such inhibition experiments. In addition, peripheral blood lymphocytes are less easily cultured in serum-free medium, mainly used for proteinase stimulation, than spleen lymphocytes. Proteinase inhibitors at high dose can interfere also with the lymphocyte response to mitogens. Therefore, appropriate controls have to be included in each experiment. Chloromethyl ketones are not only proteinase inhibitors but also alkylating agents. When added to cultures, they might interfere as much with cell metabolism as with protease activity.