Haematoporphyrin-treated murine lymphocytes: in vitro inhibition of DNA synthesis and light-mediated inactivation of cells responsible for GVHR

It has been known that haemoatoporphyrin derivative (Hpd) has a preferential distribution in tissues with high mitotic index. Furthermore, cytocidal activity of light activated Hpd within the cells has been exploited in the therapy of experimental and human cancer. It is reported here that maximum, long lasting, although reversible, inhibition of DNA synthesis was obtained in Hpd-treated lymphocytes. However, Hpd-treated lymphoid cells did not stimulate allogeneic lymphocytes in the primary mixed lymphocyte reaction (MLR) culture. Phytohaemagglutinin (PHA) stimulated murine lymphocytes treated with Hpd and exposed to laser light have shown higher susceptibility to lysis than resting, PHA unstimulated, lymphocytes. In vitro DBA/2 stimulated C57 lymphocytes, inoculated into X-irradiated BD2F1 mice, upon Hpd treatment followed by exposure to light, did not cause a lethal graft vs. host reaction (GVHR).