[Protein A: an immunomodulator in cancer patients]

Protein A defined as one of the components of the wall of Staphylococcus Aureus Cowans 1 has shown its effects as modifier of the immune response: it induce changes in cellular receptors, polyclonal activation of T and B lymphocytes, liberation of lymphokines, increase in the production of gamma-interferon (probably as the result of activation of NK cells). In the present work we have studied NK activity and its modifications by Protein A and gamma-interferon in blood of 50 patients with solid tumours. The method used was the Cr 51 liberation assay. The effectors cells were non-adherent lymphocytes treated with different doses and times of incubation of Protein A and gamma-interferon. As target cells we utilized the cellular line K-562 for NK activity and autologous tumoral cells isolated from surgical specimen for tumour-specific cytotoxicity. The results obtained allow us to state the following conclusions: 1. NK activity against K-562 cells is not always a specific parameter of such activity. 2. Tumour-specific cytotoxicity can vary according to the histological type of tumour. 3. Protein A is a potent inducer of tumour-specific cytotoxicity in a higher degree than gamma-interferon.