Tumour rejection after adoptive transfer of line-10-immune spleen cells is mediated by two T cell subpopulations

Suplatast tosilate, a new type of antiallergic agent, prevents the expression of airway hyperresponsiveness in guinea pigs

Suplatast tosilate (suplatast) is an antiallergic agent capable of down-regulating the functions of CD4+ T cells. We now investigated the effects of suplatast on the antigen-induced airway hyperresponsiveness and the underlying allergic inflammatory response in sensitized guinea pigs. Animals that had been immunized twice by ovalbumin inhalation on day 0 and day 7 developed an increased airway responsiveness against inhaled acetylcholine 24 h after the ovalbumin challenge on day 14. Suplatast (10 and 100 mg/kg per day) and ketotifen (10 mg/kg per day) given orally from day 0 to day 14 effectively inhibited the expression of airway hyperresponsiveness. They also inhibited the infiltration of eosinophils and macrophages into broncho-bronchiolar walls and lumen. Interestingly, suplatast, but not ketotifen, inhibited the infiltration of lymphocytes including CD4+ T cells. Collectively, these results strongly suggest that suplatast prevents the expression of airway hyperresponsiveness due to the ability to suppress the infiltration of inflammatory cells into lung tissues.

A helper T-cell epitope of the E7 protein of human papillomavirus type 16 in BALB/c mice

The helper T-cell response to the E7 protein of human papillomavirus type 16 (HPV16) was studied using BALB/c (H-2d) mice. Twenty-two overlapping synthetic peptides spanning the HPV16 E7 protein were split into 6 groups. Mice were sensitized using mixtures of synthetic peptides corresponding to each of the groups. Lymph node cell suspensions were cultured with the corresponding mixture of synthetic peptides that was used for sensitization. Two mixtures induced a proliferative response. Analysis of the individual peptides from these mixtures showed that two (overlapping) peptides induced a proliferative response. This response was mediated by CD4+ cells. The common region of the two peptides was found to be a single epitope, and a minimal epitope was demonstrated (AHYNIVTFCCK). In conclusion, in contrast to others, we demonstrated a helper T-cell response in BALB/c mice. This may be due to the fact that we used synthetic peptides as immunizing agent. The helper T-cell epitopes in HPV16 E7 demonstrated previously are partly overlapping with the (minimal) epitope demonstrated here, underlining the 'public' nature of the epitope.

Specific tumor memory induced by polyethylene-glycol-modified interleukin-2 requires both helper and cytotoxic T cells

Local polyethylene-glycol (PEG)-modified interleukin-2 (IL-2) immunotherapy of the guinea pig Line 10 (L10) tumor was previously demonstrated to evoke long-lasting systemic immunity after cure of the tumor and metastases. T cells, most likely the helper T cell subpopulation, were demonstrated to be crucial to the antitumor effects. Here we show that systemic immunity is induced within 7 days after the start of PEG-IL-2 therapy, indicating a rapid systemic priming of L10-specific T cells. No in vitro cytotoxic activity was detected in cell suspensions obtained from the primary tumor site, the regional lymph node or the spleen when isolated during (days 21 and 28) intratumoral treatment with 200,000 IU PEG-IL-2. These data confirm our earlier results obtained with 60,000 IU PEG-IL-2. Moreover, no cytolytic activity was observed in the chromium-release assay after in vitro restimulation with irradiated tumor cells. Specific L10 immunity can be transferred using spleen cell suspensions. Depletion of such a suspension of helper T cells resulted in rejection of the primary tumor in two out of four animals, but all the guinea pigs developed lymph node metastases. Removal of the cytotoxic/suppressor phenotype caused rejection of the dermal tumor in four of eight guinea pigs, but the capacity to prevent lymph node metastases was retained in all animals. Thus, depletion of either subtype reduces, but does not abrogate, the capacity to transfer L10 immunity with spleen cells. In conclusion, our data suggest that tumor cell killing through direct T cell cytotoxicity is not the main mode of action in PEG-IL-2-induced L10 tumor regression. PEG-IL-2 therapy induces early systemic immunity, resulting in rejection of a distant tumor, and the transfer of this immunity depends mainly on the presence of helper T cells, although cytotoxic T cells may also play a role.

Locoregional therapy with polyethylene-glycol-modified interleukin-2 of an intradermally growing hepatocellular carcinoma in the guinea pig induces T-cell-mediated antitumor activity

Therapy with repeated intratumoral and perilymphatic administration of relatively low doses of polyethylene-glycol(PEG)-modified interleukin-2 (IL-2) in the syngeneic guinea pig line 10 (L10) hepatocarcinoma results in significant local tumor growth inhibition and a delay in development of regional lymph node metastases of more than 3 weeks when compared to controls. Occasionally animals are cured of tumor. The mechanism of this antitumor activity was studied. The antitumor activity of locoregionally administered PEG-IL-2 was abrogated by pretreatment with polyclonal anti-thymocyte serum, indicating that the observed tumor growth inhibition was a T-cell-mediated phenomenon. Besides the locoregional tumor growth inhibition, a systemic effect was recorded as the growth of a second tumor cell inoculum at the contralateral side was inhibited as well. Furthermore, those animals cured after PEG-IL-2 therapy developed specific immunity against the L10 tumor and this immunity could be transferred to naive animals by spleen cells. Immunohistological observations of the tumor site revealed a slight increase of helper and cytotoxic T cell subpopulations after PEG-IL-2 therapy. More pronounced, however, was the rise in number of eosinophilic granulocytes present in the stroma surrounding the tumor cells. Involvement of cytotoxic cells in the antitumor effects of PEG-IL-2 could not be demonstrated: regional lymph node cells and spleen cells obtained immediately after therapy (day 15) or on day 21 showed no cytotoxic activity in vitro against L10, K562, Daudi and line 1 (L1) target cells. In conclusion, locoregional therapy with PEG-IL-2 induced a a systemic T-cell-mediated antitumor response. As no cytotoxic T cell activity was measured, however, the underlying mechanism is most likely a T-helper response. Eosinophils at the tumor site may be tumoricidal but further experiments must reveal the role of these cells in the PEG-IL-2-induced tumor regression.