Differential cytostatic effect of interferon on murine BALB/c B- and T-cell tumors

Synergistic effects of interferon-gamma and tumor necrosis factor against proliferation of gynecologic tumor cell lines

The cooperative effects of recombinant human tumor necrosis factor (rH-TNF) and recombinant human interferon-gamma (rH-IFN-gamma) against the proliferation of four human gynecologic tumor cell lines (HHUA, ISHIKAWA, HeLa S3, and SCH) were examined in vitro. The effect of rH-IFN-gamma on TNF receptors was also examined. ISHIKAWA and SCH cells were highly responsive to rH-TNF alone, HHUA cells exhibited a minimal degree of responsiveness to rH-TNF, and HeLa S3 cells were unresponsive to rH-TNF alone. HHUA, HeLa S3, and SCH cells were responsive dose-dependently to rH-IFN-gamma, and ISHIKAWA cells were unresponsive to rH-IFN-gamma alone. A synergistic antiproliferative effect of rH-TNF and rH-IFN-gamma appeared in HHUA, ISHIKAWA, and HeLa S3 cells. The effectiveness of rH-TNF increased in these cell lines pretreated with rH-IFN-gamma, but not vice versa. rH-IFN-gamma did not change the binding affinity of TNF receptors in the four cell lines, but increased the number of binding sites for TNF in HeLa S3 and SCH cells. These findings suggest that there is no relationship between the increase in TNF binding sites by rH-IFN-gamma and the synergistic antiproliferative effect of rH-IFN-gamma and rH-TNF. The combination therapy of rH-IFN-gamma and rH-TNF will be a new approach against cancers.

Inhibitory effects of interferon-gamma on the T suppressor cell circuit in contact sensitivity

The effects of a partially purified, splenocyte-derived murine interferon (MuIFN-gamma N) and a recombinant IFN-gamma (MuIFN-gamma R) on the T suppressor pathway and on the T effector cells of delayed type hypersensitivity were investigated in a 2,4-dinitrofluorobenzene contact sensitivity model. Various T cell subpopulations, suppressor T cells of afferent and efferent types, and an auxiliary T suppressor cells as well as a T effector cell of delayed type hypersensitivity were induced and the functions assessed in transfer experiments. Confirming the results of earlier experiments obtained with IFN-alpha, beta, the MuIFN-gamma N preparation and the rec. MuIFN-gamma R: enhanced the decreased response in animals sensitized with an antigen overload to an optimal response; inhibited the afferent-acting T suppressor cell in vivo and in vitro; inhibited the Ts-eff response; blocked the auxiliary T suppressor cell response after intravenous injection to recipients of Ts-eff cells on day 0 and 1; and did not suppress the activity of the T effector cell of delayed type hypersensitivity in vivo and in vitro (the MuIFN-gamma R was not tested). We conclude that IFN-gamma preferentially inhibited the T suppressor cell circuit of contact allergy. These results are similar to our observations on the inhibitory effects of a pure interferon-alpha, beta on the regulatory T suppressor cell circuit in contact allergy. Selective suppression of different T subpopulations by IFN-gamma may be an important regulatory mechanism in delayed type hypersensitivity.

Modulation of the growth of murine thymoma cell lines having different Lyt-phenotypes by MDP and MDP(D-D): macrophage-mediated inhibition of in vitro cell growth

The ability of N-acetylmuramyl-L-alanyl-D-isoglutamine (MDP) and its adjuvant-inactive stereoisomer, N-acetylmuramyl-D-alanyl-D-isoglutamine, (MDP(D-D] to inhibit the in vitro growth of 3 murine ascitic thymoma lines, expressing different Lyt-phenotypes, was studied. MDP inhibited the growth of all 3 cell lines. MDP(D-D) inhibited the 2 cell lines expressing Lyt-1+2- or Lyt-1+2+ phenotypes, but not the third cell line which expressed the Lyt-1-2+ phenotype. The ability of MDP or MDP(D-D) to inhibit thymoma growth was lost when the ascitic cell populations were depleted of macrophages. MDP could be replaced by a supernatant derived from an ascitic Lyt-1+2- cell population exposed to MDP. The supernatant required the presence of macrophages for activity. The inhibition by MDP of the growth of the Lyt-1-2+ cell line was prostaglandin synthetase dependent: indomethacin antagonized the inhibitory activity of MDP. The inhibition by MDP of the Lyt-1+2- cell line was partially antagonized by indomethacin, and no antagonism was observed with the Lyt-1+2+ cell line.