An Experimental System for the Simultaneous Estimation of Mitostatic and Lymphotoxic Effects of Immunosuppressants and Cytostatics

Abstract

Beginning in 1967, our laboratory has published a number of investigations of the nonsyngeneic stem ceil-inactivation phenomenon (1-3). It has been shown that, after transplantation of a mixture of allogeneic lymphoid and hemopoietic cells into lethally irradiated hosts, stem elements of the mixture are inactivated by allogenic lymphocytes of the graft. In other words, after transplantation of such a cell mixture exogenous colony-forming units (CFU) ~ give no colonies in recipient spleens. On the basis of this fact we supposed that lymphoid cells of parental genot)~pe, being transplanted into sublethally irradiated F1 recipients, must inactivate host endogenous CFU, i.e., inhibit endogenous colony formation. The degree of inhibition may serve as a quantitatively accurate value for graft-versus-host (GVH) reaction. It is evident that such an experimental system is characterized by the development of two simultaneously occurring processes: multiplication of endogenous CFU and homograft reaction against them by transplanted lymphocytes. Both processes may be quantitatively estimated by counting the number of spleen colonies in animals of corresponding experimental groups. By this technique, it is possible to compare quantitatively two of the most important actions of immunosuppressive agents: their mitostatic effect (CFU inhibition), and their lymphotoxic action; the latter is a true immunosuppressive effect, the abolition of endogenous CFU inactivation. Materials and MethodsMice (20--22 g) of CBA, C57BL/6J inbred strains and (CBA X C57BL/6J)F1 were used in the experiments. Lymph nodes were removed from CBA and C57BL/6J mice and prepared cell suspensions (2) were injected into (CBA X C57BL/6J)F1 mice in amounts varying from 0.2 to 12 X l0 s cells. 24 hr before cell transfer, recipients were irradiated with 600 R gamma rays at a dose rate of about 438 R/min. For determination of endogenous CFU number, recipients were sacrificed 9-10 days after irradiation (4).Immunosuppressaslts at various dose ranges were injected intraperitoneally into (CBA X C57BL/6J)F1 mice. The first injection of 6-MP, Imuran, or anti-lymphocyte serum (ALS) was given simultaneously with cell transfer; cyclophosphamide was administered 1-2 hr 1 Abbreviations used in this paper: ALS, anti-lymphocyte serum; CFU, colony-forming units; GVH, graft-versus-host.

Effects of cytotoxic immunosuppressants on tuberculin-sensitive lymphocytes in guinea pigs.

“…It acts both before and after initial antigenic challenge (9)(10)(11) and is capable of suppressing secondary (anamnestic) responses (24). In several studies, it appears to be a more potent imunosuppressant than phasespecific drugs such as 6-MP (25)(26)(27) and has a high therapeutic: toxic ratio (1). In other reports, cyclophosphamide has been shown to be more effective in depleting pools of small lymphocytes than phase-specific drugs (25).…”

Differential Effects of Immunosuppressants on Lymphocyte Function

“…Lymph node cells from unsensitized animals treated with a similar course of cyclophosphamide did not inhibit migration, thereby indicating that drug therapy itself did stimulate these cells to elaborate MIF. DISCUSSION Owing to differences in pharmacologic activities, immunosuppressive agents have variable effects on both lymphocyte kinetics (10,11) and immune responses (12)(13)(14)(15)(16). In these reports, the comparative effects of drugs were defined on selective parameters of lymphocyte function.…”

Studies on the immune response to Newcastle disease virus in poultry

“…Linking results in a major disruption of the DNA function and subsequent interference with normal cell mitosis and kills cells undergoing multiplication. Cyclophosphamide appears to be selectively cytotoxic for lymphocytes at intermediate doses (Petrov et al, 1971), but it does have some effect on all rapidly dividing tissues, such as the cells of the bone marrow and gastrointestinal tract (Bach, 1975).…”